The Science of Human Potential

Defending LCHF in the climate change debate

Our last post which questioned in passing aspects of the plant-based position on climate change caused quite a fuss in some circles. We were accused of being science-deniers, on a par with Trump and the anti-vaxxers, by some. There’s a recent blog about us here.


Modelling the effects of increasing fossil fuel emissions before withdrawing from the Paris Accord

The atmosphere is warming, the sea levels are rising, species are dying and habitats becoming sterile, and the major contribution – certainly the largest modifiable contribution – is the fossil fuel combustion which has gone on since the beginning of the industrial era and shows no sign of decreasing. A secondary contribution is increased methane emissions from intensive agriculture and the huge quantities of landfill waste that modern consumerism is able to generate without thought or effort. No denying that!

This is not in question. What is in question are the most effective ways to deal with it and, with regard to agriculture, what to do also about the tsunami of metabolic diseases which threaten to swamp us here in the Pacific before the sea can. People will always need food and the world will always need animals; this may not always be true for fossil fuels, which can potentially be replaced almost completely by various other forms of energy.

We are not experts in climatology, energy, or agriculture – we can only point out the things that seem obvious. One of these facts is that as long as there have been animals on earth, they have breathed out CO2 and emitted methane. They have not always burned fossil fuels (coal, gas, oil, diesel, petrol) or burned down forests. According to a 2013 FAO report, farmed ruminants contributed 14.5% to the total greenhouse gas effect, a figure which did not take into account carbon sequestration in pasture (which has not been properly measured yet) and which included ongoing deforestation, which is not a current farming practice in NZ (although it may contribute to some imported feeds).[1,2,3]

A recent modelling of 10 possible dietary patterns found that 3 dietary patterns that included some animal foods were more environmentally sustainable than a diet of only plants.[4]

Carrying capacity was generally higher for scenarios with less meat and highest for the lacto-vegetarian diet. However, the carrying capacity of the vegan diet was lower than two of the healthy omnivore diet scenarios.” 

However a limitation of this paper was that the environmental impact of meat was based on the US model of intensive beef production in feedlots, and that nutritional value was based on the US dietary guidelines, so that animal fat, full fat dairy, and organ meats were not included, making the use of animal foods much more wasteful than is necessary in the context of the LCHF diet.

One of the trends in NZ farming is that extensive farming of high country land for traditional meat and fibre herds like sheep is being replaced with intensive land use to produce dairy, with consequent harmful effects on our rivers and increased emissions. As a result of this, which is primarily to feed world markets, lamb and mutton are being priced out of the reach of New Zealanders. A further effect of this change on the environment is that wool production has decreased to be replaced with synthetic fleeces which shed minute plastic fibres into the environment when washed, killing fish and other small sealife.


Methods of production of meat from sheep and goat locally produce least GHG [2]

Environmental benefits of LCHF

There are important ways in which the LCHF diet is more sustainable than the standard diets it replaces. Here are a few we can think of….
1) the appetite control effects of the LCHF diet mean that less food will be eaten overall at a population level, and if weight loss is an effect in an overweight person, their energy requirement thereafter also goes down.
(If someone exercises then, unless they are losing weight, their need for food will increase, but no-one is telling us not to exercise; besides, the cost of exercise is partly offset by a decreased use of fossil fuel for common exercises such as cycling, walking, and running).
2) the LCHF diet supplies a mechanism (reduction of serum SFA and increased LDL particle size) by which a higher intake of saturated animal fats is less likely to be harmful; the consumption of fats from animals reduces the need for plant crops, including palm oil. The production of palm oil is an environmental scandal, but the demand for it is entirely an unintended consequence of advice to avoid animal fat.
3) the LCHF diet is not a high protein diet, includes a variety of animal and plant protein foods, and allows the use of organ meats and bone broths, another way of preventing waste and reducing the numbers of animals required to feed a population that has been entirely overlooked in dietary guidelines.
4) the LCHF diet can easily be a lacto-etc-vegetarian diet, with more difficulty has been managed as a vegan diet, and is usually a plant-based diet if by that is meant a diet in which most food, by volume, is unprocessed plants and fruit oils (however the term plant-based, as used in the literature, does seem to be entirely interchangeable with vegan). Unlike the Paleo diet LCHF includes the use of legumes, a low-environmental impact protein source, for people with a sufficiently healthy carbohydrate tolerance.

You can read some criticisms of our last post from a plant-based consultant here. We must point out that their criticism of Zoe Harcombe is out-of-date to say the least. She does have a PhD now and is a published author of important peer reviewed articles in prestigious medical journals. Her expert analysis of the biased and error-ridden Naude et al meta-analysis, which when the errors were corrected said the opposite of what its authors, six supposed experts in their field, claimed it said, helped secure the acquittal of Tim Noakes and looks set to become a textbook case of forensic statistical analysis.[5]

The Zoe Harcombe article we linked to in our last blog post did not contain her own research but quotations from a published work written by an expert in sustainable agriculture, and her conclusions from this were so reasonable and climate-aware that only someone with an ideological agenda could ignore them in favour of an ad hominem dismissal.

We wanted to comment on the blog containing these plant-based criticisms of us, but comments were not allowed. However, the author complains in his post that we had censored comments he tried to place on this blog; we have never seen such comments in moderation and would not censor them. We welcome them, so please send them in.

The author, who is friendly enough, engaged with one of us (GH) on twitter and informed us that glycotoxins from the flesh of animal species increase the risk of Alzheimer’s.

This seems to us like pseudoscientific scare-mongering  in pursuit of an ideological agenda. Firstly, even in the NIH-AARP study which was heavily weighted against red meat for mortality outcomes, red meat had a protective association with Alzheimer’s mortality alone. Secondly, the world’s oldest people have consistently been omnivores with red meat in their diets, not vegans, and have kept their wits about them to the end. Thirdly, Alzheimer’s is identified as an insulin resistance disease and the role of processed carbohydrate cannot be overlooked. Fourthly, there is no evidence that glycotoxins from meat have been related to any specific case of Alzheimer’s. Fifthly, glycotoxins are also known as AGEs and are formed from a wide variety of foods due to high-temperature cooking, not just from meat, and are also formed in the body under high-sugar conditions.

In fact the reduction of AGE exposure for health was the subject of a chapter in Dr Atkins; Age Defying Diet back in 2000AD.

Plant fibres and polyphenols normally thought to be beneficial can form large concretions called bezoars, familiar to fans of Harry Potter, in the intestines of people eating them, with deadly and painful consequences. This is a thing that actually happens – there is no doubt about it, it is not just a hypothesis like the meat->glycotoxin->Alzheimer’s claim. Should we then warn people against eating plants in case they get a bezoar? Of course not. Bezoars are extremely rare (which is why they are valuable to magicians) and result from very imbalanced diets.[6]

We’re going to stick our necks out here – you can safely eat plants without worrying about bezoars (but please don’t sue if we’re wrong).

What can we do?

Agricultural climate science, and agriculture’s role in nutrition and health, are too important to be captured by a special interest lobby which represents less than 1 percent of the population, a relatively privileged 1 percent at that, for whom climate control is not the primary motivation for the ideology, and who frequently resort to pseudoscientific scare-mongering tactics (“nutritional terrorism”) to influence people’s dietary choices.

But if you want to stop this happening, and to prevent the destruction of our planet in the most human-friendly way possible, everyone needs to take a bigger interest in the subject, and vote, shop, travel, and if necessary eat accordingly. Support farming methods you agree with and give feedback to industry when you can. Support the stalled campaign to label palm oil in food the next time you write to an MP or meet one (seriously, what is wrong with people that this didn’t happen?). We are not experts, you are not experts, but the future surely depends on what we all do much more than it depends on what the experts decree. If we sweep this issue under the rug, then we are giving away control of it.

The Bottom line – when we rediscover how to control our weight and appetite, and how to include animal fat and organ meats in our diets, we will need fewer animals and fewer plants per capita to be nourished and healthy.
Beyond this, attitudes to family planning, energy use, and the consumption of natural resources are at the root of our problems. Reduce, recycle, reuse, repair; use public transport or your own muscle power whenever possible, if not try to carpool. Use dinner leftovers for breakfast. All this will make you wealthier too – what’s not to like?


{1] Gerber, PJ, Steinfeld, H, Henderson B, Mottet A, Opio C, Dijkman J, Falcucci A and Tempio, G. Tackling Climate Change through Livestock – A Global Assessment of Emissions and Mitigation Opportunities, Food and Agriculture Organization of the United Nations, FAO 2013, Rome.

[2] Opio, C., Gerber, P., Mottet, A., Falcucci, A., Tempio, G., MacLeod, M., Vellinga, T., Henderson, B. and Steinfeld, H. (2013) Greenhouse Gas Emissions from Ruminant Supply Chains – A Global Life Cycle Assessment. Food and Agriculture Organization of the United Nations (FAO), Rome.

{3] There is a good discussion of the WHO estimates and other aspects of sustainable animal farming from Richard H Young, Policy Director of the Sustainable Food Trust and Beef cattle and sheep farmer Sustainable Food Trust, here

[4] Peters CJ, Picardy J, Darrouzet-Nardi AF et al. Carrying capacity of U.S. agricultural land: Ten diet scenarios. Elementa. 2016. DOI: 10.12952/journal.elementa.000116

[5] Harcombe Z; Noakes TD. The universities of Stellenbosch/Cape Town low-carbohydrate diet review: Mistake or mischief?. South African Medical Journal, [S.l.], v. 106, n. 12, p. 1179-1182, dec. 2016. ISSN 2078-5135.

[6] De Toledo AP, Rodrigues FH, Rodrigues MR, et al. Diospyrobezoar as a Cause of Small Bowel Obstruction. Case Reports in Gastroenterology. 2012;6(3):596-603. doi:10.1159/000343161.



Red Meat Will Kill You – and make it look like an accident.

By George Henderson and Grant Schofield

Disclaimer – we’re not recommending that people eat red meat in preference to white meat, anymore than we think people should eat red peppers instead of onions. A mixed diet of various types of animal and plant foods, as close to nature as is consistent with good hygiene, good digestion, and good eating, is the default option for good nutrition.

However, red meat epidemiology is the modern example of bad science which, because it panders to a vegetarian bias that runs along class lines, isn’t being properly criticised and is allowed to regularly misinform the public about nutrition.


The knives are out for red meat again

This latest example is particularly worth examining because its faults are very clear and give an insight into what may have gone wrong with other studies of this sort behind the scenes.[1] They even allow us to make recommendations about how to improve these studies in future.

The BMJ has published a “new” epidemiological paper from the NIH-AARP study (based on FFQs sent in by mail from half-a million people, an impressive number) in which red meat – compared with white meat, which includes both chicken and fish – is associated with an increased risk of cancer, heart disease, and all-cause mortality.

This comes along with no less than two accompanying editorials one from Professor Potter, from Massey University NZ telling us to give up meat for the sake of our health and the planet’s.[2] Just what you’d expect, right? All those warnings about red meat couldn’t be for no reason, and all that stuff about TMAO, haeme iron, and saturated fat has to mean something, right? And those cow burps and farts have to be worse than dinosaur burps, mammoth burps, or bison burps ever were, right?


Not so fast – there are even stronger associations between unprocessed red meat and liver disease mortality and respiratory disease mortality. How did that happen? The authors are left floundering around for explanations – they settle on nitrites and nitrates. But hang on – the association is for unprocessed red meat, and not for processed white meat, so that makes no sense. And we know that saturated fat, as found in beef fat, protects against alcoholic liver disease, whereas polyunsaturated fat, as found in chicken, makes it worse – and this is a very strong, consistent, and reliable experimental finding – so, what gives?[3]

Luckily an earlier paper also looked at the same data sets, and this allows us to clearly see what went on.

In the 2009 paper that looked at the same aspect of the NIH-AARP data – red meat, white meat, and mortality – in a slightly different way (i.e. without the dodgy and unrealistic “substitution” analysis), the associations between unprocessed red meat and accidental death in men, HR 1.26 (1.04-1.54), were as great (albeit with slightly wider CIs) as the associations for cancer mortality, HR 1.22 (1.16-1.29) or CVD mortality, HR 1.27 (1.20-1.35). There was a comparable protective association between white meat and accidental death which was non-significant after adjustment.[4]

So what’s the biological mechanism by which red meat causes accidental death in men? If anything, the cognitive effects of deficiencies of red meat nutrients such as vitamin B12 suggest that an unconfounded relationship should run in the opposite direction. Men’s risk of accidental injury mortality in the US is 2-3x that of women, accidental death rates in NIH-AARP were low, and the association was not seen in women. However women’s accidental deaths may be less due to risk-taking behaviour than the deaths of men (for example if women are more likely to be victims in vehicular accidents caused by men than by women); so accidental death in men is by far the bulk of deaths caused by accidents in the NIH-AARP population (similar to the gender difference in deaths from heart attacks).

The finding for accidental death gives us some idea of the effect of healthy-user bias in this population. Perhaps men who ignored health warnings about red meat and did not replace it with white meats (or vegetable protein) were more likely to ignore basic health and safety advice, or work in dangerous workplaces. Dangerous workplaces are also places where one can be exposed to carcinogens and pollutants which increase cardiovascular risk. People who ignore health warnings about red meat are also likely to ignore warnings about sugar-sweetened beverages, and highest intake of fructose from SSBs was also associated with cardiovascular mortality in NIH-AARP.[5]

Who can spot the possible confounding in this sort of study? Give yourself a pat on the back if you can…’ll be ahead of some of the more claimed epidemiologists in modern nutrition science!

The potential for healthy user bias can clearly be seen in the baseline data (Table 1), with many more men, a more than doubled rate of smoking, and a mean BMI of 28.3 vs 25.8 in the highest red meat quintile.[1] Good luck adjusting for all that. And what does this adjustment mean in reality anyway? It is a mythical person.

For some reason accidental death was dropped as an outcome of interest in the current study, concealing important information about the likely effect of healthy-user bias on the results, and the analysis did not include adjustment for fructose, high-GI carbs, or other nutrients of interest.

Risk-taking behaviour and workplace safety are even more important considerations with regard to the two strongest associations in the BMJ paper, liver disease mortality (risk of both viral infection and hepatotoxicity from drug-taking) and respiratory mortality (pollutant exposure), causes of death which lack mechanisms sufficient to explain the strength of association with red meat in this paper.

Mechanisms run both ways

But what about the mechanisms? Doesn’t heme iron cause cancer, and TMAO from red meat cause heart disease?

The truth is probably more complicated than that. For example, heme iron can interact with other chemicals to increase production of the hydroxyl free radical, which can damage DNA, but it’s also needed for the catalase enzyme that turns peroxide radicals to water, and the CYP450 enzymes that detoxify most of the carcinogens we’re exposed to, among other things. This may help explain why, in those rare studies that control for healthy-user bias by matching sets of individuals, vegetarian and vegan diets are associated with more cancer, not less.[6,7]

Although TMAO levels in serum are associated with cardiovascular mortality, high TMAO levels are likely to be a warning sign of kidney disease, or some other metabolic disorder, rather than a causative agent.

The evidence for this is 1) that chemicals which are precursors for TMAO are found in large amounts in nuts and fish, which are negatively associated with CVD mortality, 2) that carnitine, the precursor of TMAO found in meat, prevents heart attacks when given in large doses as a supplement to patients with established heart disease.[8]
The evidence seems to say that, while there are mechanisms by which red meat can cause CVD and cancer, there are also mechanisms by which red meat can prevent CVD and cancer, and at a population level these mechanisms, if they are important, seem to cancel each other out anyway in health-conscious individuals who choose to eat meat.
There is however evidence for limiting red meat (or donating blood) in persons with high ferritin levels, especially with the genetic condition known as familial haemochromatosis.

But what about the planetary health?

In New Zealand, lamb and beef, venison and goat (but not so much dairy) are being farmed on pasture land established a couple of centuries ago, and watered with the rain, whereas pork and chicken, even free-range chicken, are being fed grains and soy, much like factory farmed beef in the US. Red meat (other than pork) as grown in NZ is thus not bad for the planet, but instead sequesters carbon, fertilises the land, and maintains the stability of topsoil undermined by plant monoculture farming (which is how plant crops are grown outside market gardens and organic or semi-organic mixed-farming model farms these days). We waste food by not eating as much organ meat, fat, and bone as we used to (because we’ve been indoctrinated by health experts to eat “lean meat”, i.e. the more expensive muscle meat, and throw the rest away), and this is not great for the planet. Zoe Harcombe has written a more detailed analysis of the environmental claims in Professor Potter’s editorial here.

New Zealanders do not eat “too much” red meat in any case. The 2008/9 NZ Adult Nutrition Survey showed that Kiwis consumed more iron and protein from grains than from all animal foods combined. When you consider that animal food including meat is a very good source of these nutrients and grains are (or ought to be, in the natural, whole grain, state) a very poor source, this might suggest that the average Kiwi diet is either badly out of proportion or over-processed or (our bet would be) both.

Improvements suggested

We can think of ways to protect future epidemiological studies from the inaccuracies likely to be in this latest one.
1) Always give results for accidental death, ideally for men and women separately, in any mortality analysis. This will allow some assessment of healthy-user bias. (Injury requiring hospitalisation rates could be given in papers without mortality outcomes).
In the BMJ paper, the authors already knew about the association with accidental death from their 2009 paper but chose not to include it when they were being funded by the WHO, an organisation that seems to have taken up an activist position against red meat to go with its already dated position on salt and saturated fat.
2) Where possible, give subgroup results for closely matched, and equally health conscious, subjects; those with the same income, BMI, smoking rates, ethnicity and gender balance, etc.
We also think it would be a good idea if professors of agriculture, preferably ones with farming experience, wrote more editorials about planetary health, if that’s what the medical journals are after.


[1] Etemadi A, Sinha R, Ward MH et al. Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study

[2] Potter JD. Red and processed meat, and human and planetary health

[3] Kirpich IA, Miller ME, Cave MC, Joshi-Barve S, McClain CJ. Alcoholic Liver Disease: Update on the Role of Dietary Fat. Osna N, Kharbanda K, eds. Biomolecules. 2016;6(1):1. doi:10.3390/biom6010001.

[4] Sinha R, Cross AJ, Graubard BI, Leitzmann MF, Schatzkin A. Meat intake and mortality: a prospective study of over half a million people. Archives of internal medicine. 2009;169(6):562-571. doi:10.1001/archinternmed.2009.6.

[5] Tasevska N, Park Y, Jiao L, Hollenbeck A, Subar AF, Potischman N. Sugars and risk of mortality in the NIH-AARP Diet and Health Study. The American Journal of Clinical Nutrition. 2014;99(5):1077-1088. doi:10.3945/ajcn.113.069369.

[6] Burkert NT, Muckenhuber J, Großschädl F, Rásky E, Freidl W. Nutrition and Health – The Association between Eating Behavior and Various Health Parameters: A Matched Sample Study.
PlosOne: February 7, 2014

[7] Key TJ, Appleby PN, Spencer EA et al. Cancer incidence in vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr. 2009 May;89(5):1620S-1626S. doi: 10.3945/ajcn.2009.26736M.

[8] DiNicolantonio JJ, Lavie CJ, Fares H, Menezes AR, O’Keefe JH. L-carnitine in the secondary prevention of cardiovascular disease: systematic review and meta-analysis. Mayo Clin Proc. 2013 Jun;88(6):544-51. doi: 10.1016/j.mayocp.2013.02.007. Epub 2013 Apr 15.


NZ case study; A citizen scientist controls autoimmune diabetes without insulin, with a low carb diet, a glucose meter, and metformin.

The case study is a very important type of medical publication that’s overlooked in this age of big data. Unlike large statistical studies, which tell you the probability of something happening, the case study tells you whether something CAN happen at all, and under exactly which circumstances it has happened.

Case studies answer questions like “Can autoimmune diabetes, with lower insulin production, be managed long-term without insulin?”

Yes, it can, and this is described in full detail and a clear and simple style in a new case-study from Christchurch.[1]
2017 Nelson Jacobs Case report Management of autoimmune diabetes without insulin

This is published on, an online data repostitory set up by people involved in CERN and other places. Warrick Nelson, the first author is the patient and is an operations manager at Plant and Food Research in NZ. The second author is his doctor. This is citizen science.  We love it.

So onto the topic of diabetes, and  management of the condition with low carb diets……

We reviewed the strong evidence for low carb diets in diabetes management in the New Zealand Medical Journal in a 2016 review cited in the current paper.[2]

Its case study is a great example of how the wisdom of Citizen Scientists, equipped with mass produced measuring devices and, in this case, a proven medicine, can discover the one way to treat a disease. It is written up by the patient and his doctor, who was wise enough to recognise this as the teachable moment it is.

The patient first presented with type 2 diabetes, non-alcoholic fatty liver disease, insulin resistance, and a high risk TG/HDL ratio. He was highly motivated and was able to lose weight and correct all of these issues with a better diet and metformin alone.

In early 2013 the patient, a white male 53 years of age, was diagnosed diabetic following a routine screening test, based on fasting glucose of 10.8 mmol/L and HbA1c of 58 mmol/mol (7.5%). Mild overweight, especially abdominal, mild hypertension, mild dyslipidaemia and elevated liver function panel (Table 1) indicated the onset of T2D. Metformin 500mg twice daily and 10kg weight loss were indicated. Advice on weight loss was primarily calorie control (particularly between-meal calories, as the patient self-reported a tendency to snack in the evenings on biscuits). Snacks were recommended to be reduced and cheese or almonds suggested as options. The patient was highly motivated and within nine months HbA1c test showed a pleasing result at 37 mmol/mol (5.5%) and BMI of 26 (Table 1).

A year later and the patient has signs of Type 1 Diabetes, this pattern is known as Latent Autoimmune Diabetes of the Adult (LADA).

However, a year later a routine HbA1c of 83 mmol/mol (9.7%) occurred, associated with unexplained weight loss and fatigue. By this time, the BMI target was very close to achievement. Anti-GAD tests were ordered on the assumption it was likely the patient had resolved to a Type 1 diabetic pattern. The result was unrecordably high autoantibodies and the patient was referred to a specialist diabetes clinic to begin insulin therapy.

But in the meantime the patient has begun testing post-meal blood sugars and eating accordingly – note that the doctors or dietitians had already recommended eating almonds or cheese instead of biscuits in the weight-loss phase, so he has a general idea of the alternatives.

In the interim, the patient had begun using a home glucose meter with nearly immediate resolution of blood glucose from the 15-23 mmol/L range to sub-10 postprandial tests (Figure 1). This was achieved by an immediate drastic reduction of bulk dietary carbohydrates, primarily experimenting with reducing carbohydrate intake to achieve acceptable postprandial glucose levels. A food diary indicated sub 100g carbohydrate per day, and more stringent dietary intervention from January 2015 suggests <75g/day is being achieved.
The patient attended two clinic visits, but expressed reluctance to begin insulin therapy while home blood glucose testing indicated dietary interventions were working. At this time, HbA1c had already reverted to 49 mmol/mol (6.6%) and by the second visit, 3 months later, was down to 38 mmol/mol (5.6%). Further autoantibody tests indicated both IA2 and ICA at the top of the measurable range. A fasting insulin test returned 66pmol/L.

But can it be healthy, eating such a restricted diet?

The patient reports the new diet is completely satisfying, tasty and easy to manage other than when faced with commercial food offerings eaten away from home. In particular, airline and hospital “diabetes” choices are completely incompatible with a low carbohydrate diet. The patient reports completely removing wheat flour products (such as breads, cake/biscuits, pasta, couscous), potato, rice, maize and other obvious high starch products (including gluten free options such as quinoa and buckwheat). The dietary bulk provided by these foods is largely replaced with salad and vegetable as appropriate. High carbohydrate vegetables (such as carrots, pumpkin, green peas) are not eliminated, but are eaten in moderation.

But surely the results are not sustainable?

Quarterly HbA1c tests have remained at ≤40 mmol/mol (≤5.8%) for two years on this diet. The patient has felt confident to reduce the frequency of home blood glucose testing to one day per week of pre/post prandial testing for one or two meals on that day plus occasional testing following introduction of new food items.

LADAThe authors discuss how failing islet beta-cells in late-onset diabetes tend to keep producing low levels of insulin (we think this might be more likely if they’re protected from lipotoxicity – excess fat – and glucotoxicity – excess sugar; the weight loss phase where NAFLD was reversed would have helped avoid the former, the low carb diet the latter).[3] We have theorised previously that the different gut hormone responses to a low carbohydrate meal, which include a lower release of glucagon and a higher release of somatostatin 28, can contribute to controlling post-prandial glycogenolysis, lipolysis, and proteolysis at a lower insulin level.

Reading this report, we are bystanders at a revolution in medicine. This patient has decompensated diabetes, and it’s unlikely any variation on a higher carbohydrate diet would be able to control their blood sugar without insulin. In fact, the hospital diabetes diet is completely unsuitable for this purpose. If the low carb diet is suitable, and the hospital diet isn’t, for this critical aspect of diabetes management, what then?

Hospital diabetes diets are generally the high-carb, low fat, dietary guidelines type of diet that was introduced into diabetes care without any RCT comparison with the low carbohydrate (<130g/day CHO) or very low carbohydrate (<50g/day CHO) diabetes diets that have outperformed it in RCTs ever since.[2] These diets are normally grain based, nutritionally poor, and high in glycemic load. Their only concession to diabetes management is that the carbs are counted and (supposed to be) spread throughout the day. They require higher insulin dosing than would be the case with low carb diets, and thus make it harder to maintain blood sugars safely within the normal, non-diabetic range, so higher cut-offs are accepted as “good management”.[2] This case, as well as the evidence we included in our review, and a more recent RCT of a low carb diet (70g/day CHO) for type 1 diabetes published by Jeremy Krebs’s team in New Zealand,[4] show that this approach needs to change.


[1] Nelson W, Jacobs P. Management of autoimmune diabetes for two years without insulin treatment: a case report. May 7 2017 doi:10.5281/zenodo.572338.svg
2017 Nelson Jacobs Case report Management of autoimmune diabetes without insulin

[2] Schofield G, Henderson G, Thornley S, Crofts C.
Very low-carbohydrate diets in the management of diabetes revisited.
NZMJ. 2016;129:1432.

[3] Schofield G, Henderson G, Crofts C, Thornley S.
What are we to think when results from mouse research contradict those from human experiments and clinical practice? Nutrition & Diabetes (2016) 6, e224; doi:10.1038/nutd.2016.31

[4] Krebs JD, Parry Strong A, Cresswell P, Reynolds AN, Hanna A, Haeusler S.
A randomised trial of the feasibility of a low carbohydrate diet vs standard carbohydrate counting in adults with type 1 diabetes taking body weight into account.
Asia Pac J Clin Nutr. 2016;25(1):78-84. doi: 10.6133/apjcn.2016.25.1.11.




The battle over the causes of cardiovascular disease heats up!

By George Henderson and Grant Schofield

In today’s Guardian, there’s a report on the backlash against an editorial in the British Journal of Sports Medicine entitled “Saturated fat does not clog the arteries: coronary heart disease is a chronic inflammatory condition, the risk of which can be effectively reduced from healthy lifestyle interventions”.[1]

The authors are cardiologists Aseem Malhotra and Pascal Meier, well known for their support of low carb interventions (Pascal Meier is also editor of BMJ Open Heart). And, coming as a surprise to us, Rita Redberg, a cardiologist who is better known as the editor of the high-impact American journal JAMA Internal Medicine (perhaps making this the first meta-editorial). We recently had a letter published in JAMA Int Med questioning the analysis in a Harvard epidemiology paper concerning dietary fats and mortality (Wang response), so maybe this shouldn’t have been a surprise if they’re open to readers questioning the established wisdom.

The editor of BMJ British Journal of Sports Medicine has supported low carb in the past, publishing papers by Tim Noakes and Aseem Malhotra; there’s a fine tradition of the “reforming journal” which is being revived around the dietary guidelines question today, with some journals (the BMJ itself also comes to mind) not being afraid to court controversy.


The gist of the article is in the graphic above and in this press release:

Journals from BMJ Press Release:

Embargoed 23.30 hours UK time Tuesday 25 April 2017


Popular belief that saturated fats clog up arteries “plain wrong” say experts

Best form of prevention and treatment are ‘real’ food and a brisk 22 minute daily walk

The widely held belief among doctors and the public that saturated fats clog up the arteries, and so cause coronary heart disease, is just “plain wrong,” contend experts in an editorial published online in the British Journal of Sports Medicine.

It’s time to shift the focus away from lowering blood fats and cutting out dietary saturated fat, to instead emphasising the importance of eating “real food,” taking a brisk daily walk, and minimising stress to stave off heart disease, they insist.

Coronary artery heart disease is a chronic inflammatory condition which responds to a Mediterranean style diet rich in the anti-inflammatory compounds found in nuts, extra virgin olive oil, vegetables and oily fish, they emphasise.

In support of their argument Cardiologists Dr Aseem Malhotra, of Lister Hospital, Stevenage, Professor Rita Redberg of UCSF School of Medicine, San Francisco (editor of JAMA Internal medicine) and Pascal Meier of University Hospital Geneva and University College London (editor of BMJ Open Heart) cite evidence reviews showing no association between consumption of saturated fat and heightened risk of cardiovascular disease, diabetes, and death.

And the limitations of the current ‘plumbing theory’ are writ large in a series of clinical trials showing that inserting a stent (stainless steel mesh) to widen narrowed arteries fails to reduce the risk of heart attack or death, they say.

“Decades of emphasis on the primacy of lowering plasma cholesterol, as if this was an end in itself and driving a market of ‘proven to lower cholesterol’ and ‘low fat’ foods and medications, has been misguided,” they contend.

Selective reporting of the data may account for these misconceptions, they suggest.

A high total cholesterol to high density lipoprotein (HDL) ratio is the best predictor of cardiovascular disease risk, rather than low density lipoprotein (LDL). And this ratio can be rapidly reduced with dietary changes such as replacing refined carbohydrates with healthy high fat foods (such as nuts and olive oil), they say.

A key aspect of coronary heart disease prevention is exercise, and a little goes a long way, they say. Just 30 minutes of moderate activity a day three or more times a week works wonders for reducing biological risk factors for sedentary adults, they point out.

And the impact of chronic stress should not be overlooked because it puts the body’s inflammatory response on permanent high alert, they say.

All in all, a healthy diet, regular exercise, and stress reduction will not only boost quality of life but will curb the risk of death from cardiovascular disease and all causes, they insist.

“It is time to shift the public health message in the prevention and treatment of coronary artery disease away from measuring serum lipids and reducing dietary saturated fat,” they write.

“Coronary artery disease is a chronic inflammatory disease and it can be reduced effectively by walking 22 minutes a day and eating real food.”

But, they point out: “There is no business model or market to help spread this simple yet powerful intervention.”

The push-back in the Guardian made use of the Hooper at al 2015 meta-analysis of diet-heart RCTs:[2]

Dr Amitava Banrejee, a senior clinical lecturer in clinical data science and honorary consultant cardiologist at UCL, said: “Unfortunately the authors have reported evidence simplistically and selectively. They failed to cite a rigorous Cochrane systematic review which concluded that cutting down dietary saturated fat was associated with a 17% reduction in cardiovascular events, including CHD, on the basis of 15 randomised trials.”

This is nonsense.

1) The Hooper 2015 Cochrane meta-analysis gave no information on reducing saturated fat, because the only reduction in events was seen in some studies where saturated fat was replaced with polyunsaturated fat, not with carbohydrate. Based on population epidemiology, it’s likely that replacing carbohydrate with PUFA – and keeping SFA the same – would have had as much or a greater effect, except that this was never tested in these RCTs.

2) There were no reductions in heart attacks, strokes, cardiovascular deaths, or all-cause mortality from saturated fat replacement in Hooper 2015. The only reductions were in “unblinded” event outcomes, where the LDL level is one of the diagnostic criteria.

3) Hooper 2015 included many studies in which SFA was reduced by replacing processed food (pizzas, pies, desserts) with wholefoods (nuts, whole grains, fish, fruit). This improvement in food quality should have produced some benefit independent of fats. Ramsden et al isolated those studies where PUFA cooking fats and spreads replaced more saturated cooking fats and spreads, and there was no benefit overall, with some harm from high omega-6 interventions and a suggestion of benefit from omega-3 ones.[3] In fact, the Hooper et al studies that improved food quality should have produced better results than they did, and it is possible that the focus on saturated fat reduction and on keeping total fat low hampered them.

4) Statistical modelling in Hooper et al 2015 used the random effects model, which may have exaggerated the results of the smaller, more favourable trials; had an alternative model, inverse heterogeneity analysis, been used there would have probably been no significant associations at all. Watch this space as we (led by epidemiologist Dr Simon Thornley) prepare to publish an academic paper on exactly this, with a full reanalysis of this Hooper Cochrane review using this new more modern method for the meta-analysis.

Quite a few people cited in the Guardian did support Malhotra et al.

Gaynor Bussell, a dietitian and member of the British Dietetic Association, also offered the authors qualified support. “Many of us now feel that a predominantly Med-style diet can be healthy with slightly more fats and fewer carbs, provided the fats are ‘good’ – such as in olive oil, nuts or avocados,” she said.

However, saturated fats should comprise no more than 11% of anyone’s food intake, she said – far less than the 41% fat level backed by the co-authors.

While carbohydrates should still be part of every meal, people should routinely consume high fibre or wholegrain versions, Bussell said.

Well, this is nonsense. You could easily have a 41% fat diet that was 11% saturated fat if you used some olive oil. Fancy a dietitian and member of the British Dietetic Association making that mistake. But why should saturated fats comprise no more than 11% of anyone’s food (energy) intake? What is the evidence for this cut-off? It is 14% in Scandinavia, 10% in New Zealand – irrespective of the total fat intake which it’s part of, which is surely relevant; did every country pull their figure out of a hat?
And why should carbohydrates, that is, sweet and starchy foods, be part of every meal?
We think it’s probably beneficial to be in at least mild ketosis, and have low insulin levels, for at least part of the day. Otherwise you’re always in the fed state, always packing away energy as cholesterol and fat, instead of using it up. And surely that’s where the fat that can build up in your arteries comes from – whatever puts it there, whether it’s carried there by oxidised LDL particles or by magic pixies, it’s available to go there because it wasn’t used to fuel you, which is why CHD risk due to atherosclerosis is associated with overweight and obesity and offset by exercise.

There’s one criticism that’s probably justified;

Christine Williams, professor of human nutrition at Reading University, said the cardiologists’ dietary advice was impractical, especially for poorer people. “The nature of their public health advice appears to be one of ‘let them eat nuts and olive oil’ with no consideration of how this might be successfully achieved in the UK general population and in people of different ages, socioeconomic backgrounds or dietary preferences,” she said.

Doctors’ visits and PCSK9 inhibitors aren’t cheap either. There is a need to scale healthy low-carb advice for poorer populations. Fats like olive oil are cheap per calorie compared to most healthy foods, but dearer than other oils, so would some canola oil be okay? As far as anyone knows, peanuts and sesame and sunflower seeds are as good as the more expensive nuts. High-fat yoghurts and milk are the same price as the reduced fat versions; this is one way to save money. Whole grains are much more expensive than flour and sugar, but that won’t stop the experts recommending them.


In case you think that “inflammation” in the BMJ Sports Medicine editorial was too briefly described or explained, here’s a superb review of the “alternative hypothesis” of heart disease from 2011, which deserves to be more widely read.
Kuipers et al


[1] Malhotra A, Redberg RF, Meier P. Saturated fat does not clog the arteries: coronary heart disease is a chronic inflammatory condition, the risk of which can be effectively reduced from healthy lifestyle interventions. 

[2] Hooper L, Martin N, Abdelhamid A, Davey Smith G. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database of Systematic Reviews 2015, Issue 6. Art. No.: CD011737. DOI: 10.1002/14651858.CD011737.

[3] Ramsden CE , Zamora D , Majchrzak-Hong S , et al . Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota coronary experiment (1968-73). BMJ 2016;353:i1246. doi:10.1136/bmj.i1246

The fat emperor again

Ivor Cummings latest talk is worth a watch. He basically does my entire third year “Lifestyle Disease” class in a single lecture. So you can save taking that and just watch this.

I don’t buy the whole “you have to be an engineer to have a problem solving brain” line Ivor.  I’ve heard enough of that from my Dad over the years, who is also an engineer.  True though, they are both good problem solvers.

The BROAD study – a super-low fat vegan intervention for weight loss

reasons-to-go-vegan.pngBy George Henderson and Grant Schofield

There are few diet trials published from New Zealand, so we’re always keen to see them; and there are even fewer vegan diet trials.

We are even more interested when they go beyond their data, and start in on a sort of zealot approach to running down low carb diets which this study gives no insight into.

So what did they do? They went vegan (plant only) That is, we think this was a vegan study, because it’s called a “whole food plant based diet”, well-known vegan doctors are cited in the supplementary materials, dietary fat intakes were, though not measured, intended to be very low indeed, and because B12 supplements were supplied, but few details about the intervention are given, and even fewer about the controls; these received “standard medical care” with no diet advice mentioned.

The study was small (n=65) and not as representative as the authors might have hoped for; “The intervention involved patients from a group general practice in Gisborne, the region with New Zealand’s highest rates of socioeconomic deprivation, obesity and type 2 diabetes” – however, after randomisation there were only 3 Māori with 30 NZ European in the intervention arm (n=33) whereas the control arm had 21 European, 5 Māori and 6 other (n=32).

The results were excellent in terms of weight loss, and good in terms of medication reduction, with a couple of people reversing diabetes. Weight lost was as great as in the best ketogenic diet trials, although the controls here, with no diet change (or else useless advice based on NZ government recommendations? It would be good to know) provided no competition.


“The mechanism for this is likely the reduction in the energy density of the food consumed (lower fat, higher water and fibre). Multiple intervention participants stated ‘not being hungry’ was important in enabling adherence.” In other words, de facto calorie restriction is likely to have occurred, due to greater satiety per calorie, the same as mooted in LCHF studies.

The weight changes at 3 months don’t compare too badly with the weight changes at 10 weeks in the first report from this long term ketogenic diet study. [2] The reductions in medication and reversals of diabetes are greater in the ketogenic diet study, with a similar intensity of intervention, but nonetheless the BROAD weight loss results are very good by the standards of most diet trials.


So the Whole food plant-based (WFPB) diet didn’t do too badly for weight loss; what about other parameters?

In our opinion this is where the BROAD study lets itself down; it’s not that these results are terrible, but that the discussion of them, such as it is, amounts to special pleading. HDL was low (“high risk”) at baseline – 1.3 mmol/l in the intervention arm; HDL didn’t change, but the TG/HDL ratio deteriorated from 2.835 to 3.170.

“CVD Risk Assessment tools are widely used in New Zealand, and although we saw intervention WC, BMI and HbA1c improve, the between-group CVD RA (which does not account for some of these) did not change significantly. Also, HDL-cholesterol tends to decrease on a plant-based diet, and previous research had shown this ‘may not be helpful for predicting cardiovascular risk in individuals consuming a low-fat, plant-based diet’. Our analysis corroborates that this tool is not particularly appropriate for those consuming a WFPB diet.”

Now, this may well be true, but the reference for this claim is one 30-day cohort study (no comparison arm) using the same kind of wishful thinking.[3] What would be more convincing would be a mechanistic explanation of why lower HDL levels are tolerable on a very low fat diet, maybe through the diet’s effect on HDL subtype, or HDL efflux capacity, or an interaction with very low LDL, demonstrated in feeding studies. However, LDL in the intervention arm was 3 mmol/l at 12 months which though almost within target is not especially low, and the TG/HDL ratio predicts that the percentage of small dense LDL will be relatively high, so we do need more than wishful thinking before discounting the relevance of these scores. If we were to claim that a lack of effect on LDL didn’t matter in a low carb study, we would have no shortage of mechanistic evidence from feeding studies and risk factor studies to explain why; there is a huge body of scientific investigation about lipoproteins that can be relevant to these sorts of cases.

Where the discussion goes badly wrong is in attacking LCHF diets using evidence that is thin and irrelevant. The numbers of people in LCHF trials and feeding studies has become large enough that patterns of adverse outcomes can be decided by the evidence from these studies. As prior to recent years very few people in the general population ate LCHF diets, epidemiological studies don’t give us this evidence.

So what do we get, by way of a discussion of superiority?

Reviews comparing the WFPB approach to other diets show similar weight loss at 12 months for low-carbohydrate and low-fat diet approaches. However, studies on the effects of low-carbohydrate diets have shown higher rates of all-cause mortality,54 decreased peripheral flow-mediated dilation,55worsening of coronary artery disease,56 and increased rates of constipation, headache, halitosis, muscle cramps, general weakness and rash.

This isn’t good enough. Reference 54, Noto et al, is a notorious mishmash of epidemiological studies, uses an idiosyncratic and unrealistic scoring system, is mostly concerned with protein (or at least certainly conflated with it),  and includes no evidence from low carbohydrate diet trials. In fact, because more recent evidence shows that higher fat intake was associated with lower mortality in the Nurses Health Study and Health Professionals Follow up Study, and lower cardiovascular mortality in the Malmo Diet and Cancer study, not to mention the forthcoming PURE study, this line of evidence, even were it admissible, is no longer supportive of the claim. Reference 55 combines 5 studies only one of which had significant results – in any case, FMD is an insulin-mediated response to glucose in the bloodstream and its reduction, while possibly undesirable and indicative of insulin resistance on a high-carb diet, would seem to be a normal adaptation to the absence of carbohydrate. Reference 56 relates to people eating high protein during an uncontrolled low fat, high carbohydrate intervention – how high, and what else did they eat differently? It’s impossible to tell from the paper, which is a singularly inappropriate piece of evidence to use in an attack on low carb.

What about “increased rates of constipation, headache, halitosis, muscle cramps, general weakness and rash”? Some of these are expected temporary effects of keto-adaptation or of insufficient salt intake during low-carb induced natriuresis. Rash can result from increased intake of unrefined plant foods in people who are salicylate-intolerant, so is a possible side effect of vegan diets too.

The greatest weakness of this paper is its failure to discuss at all two findings; firstly that blood pressure increased on the WFPB diet. This was not statistically significant (p=0.06) but as it is an underpowered trial and this result ran counter to expectations it is worth explaining; possibly a reduction in medication can account for it.

Secondly, one person in the intervention arm had their gallbladder removed due to gallstones at 5 months. This is a known adverse effect of weight loss on a very low fat diet.[4,5] It was the subject of a 2014 meta-analysis, which found that “diets high in fat content reduced gallstones, compared with those with low fat content (risk ratio, 0.09; 95% CI, 0.01-0.61)”.[6] This would seem to be more serious than the known side effects of low carb diets. Though the one event of this sort in BROAD cannot be statistically significant, the authors (and reviewers) should have been aware of similar occurrences in other trials, making this an important risk to discuss.

Adherence at 12 months was 70% but no-one’s reason for dropping out was given.
(The informed consent phase meant that people who agreed to be in the study were aware that a vegan diet would be the only diet they were likely to get. This could be seen as a different situation in terms of self-selection bias from those studies which offer an equal chance of getting a low carb diet or a calorie-restricted 30% fat diet; people who didn’t specifically want a vegan diet could opt out, knowing their care would be the same, whereas with a two-diet comparison people may be more likely to enter the study but drop out after learning what diet they have been randomised to.)

Although this study obtained very good results in terms of weight loss, a definite win for its participants, the authors’ unwillingness to discuss possible negatives and their over-eagerness to attack low carb interventions without real evidence (they should have saved their bile for the “usual medical care” that failed their patients) do not enhance this paper’s value.

Nor does the appeal to the environmental sustainability and greenhouse gas footprint, which depends on a 2014 UK modelling paper. It all depends what foods you eat – at present these models use the lean meat, low fat dairy recommendations; however, animal fat and organ meat are wasted products, adding up to a lot of energy and nutrition, of producing these that we could use a lot more wisely. A vegan diet will have a larger environmental impact if you need to eat more imported food and out-of-season (not a problem with NZ beef and lamb) and food with a higher water content, which isn’t a very economical use of land. Raising monoculture plant crops uses more fossil fuels and has a worse effect on the land than raising ruminants the way we do in New Zealand (something you might miss with a UK model, where a lot of meat is imported). It is early days for that kind of research and all we have so far is speculative models based on assumptions.

Take homes? This trial tells us little about eating meat. It shows that getting off sugar, and refined foods has a good effect on short and medium term weight loss on this intensive intervention group compared to usual care. However an effect may be the worsening of some CVD risk factors, although what this really means isn’t clear. It says nothing about low carb healthy fat eating.


[1] Wright N, Wilson L, Smith M, Duncan B, McHugh P. The BROAD study: A randomised controlled trial using a whole food plant-based diet in the community for obesity, ischaemic heart disease or diabetes. Nutrition & Diabetes. 2017; 7(e256) doi:10.1038/nutd.2017.3.

[2] McKenzie AL, Hallberg SJ, Creighton BC, Volk BM, Link TM, Abner MK, Glon RM, McCarter JP, Volek JS, Phinney SD
A Novel Intervention Including Individualized Nutritional Recommendations Reduces Hemoglobin A1c Level, Medication Use, and Weight in Type 2 Diabetes
JMIR Diabetes 2017;2(1):e5. DOI: 10.2196/diabetes.6981

[3] Kent L, Morton D, Rankin P, et al. The effect of a low-fat, plant-based lifestyle intervention (CHIP) on serum HDL levels and the implications for metabolic syndrome status – a cohort study. Nutrition & Metabolism. 2013;10:58. doi:10.1186/1743-7075-10-58.

[4] Festi D, Colecchia A, Orsini M, et al. Gallbladder motility and gallstone formation in obese patients following very low calorie diets. Use it (fat) to lose it (well). Int J Obes Relat Metab Disord. 1998; 22(6):592-600.

[5] Gebhard RL, Prigge WF, Ansel HJ, Schlasner L, Ketover SR, Sande D, Holtmeier K, Peterson FJ. The role of gallbladder emptying in gallstone formation during diet-induced rapid weight loss. Hepatology. 1996; 24(3):544-8.

[6] Stokes CS, Gluud LL, Casper M, Lammert F. Ursodeoxycholic acid and diets higher in fat prevent gallbladder stones during weight loss: a meta-analysis of randomized controlled trials. Clin Gastroenterol Hepatol. 2014 Jul;12(7):1090-1100.e2; quiz e61. doi: 10.1016/j.cgh.2013.11.031. Epub 2013 Dec 7.


What Really Happens to Saturated Fat on a Low Carb Diet?


In our last post, we went into a lot of detail about specific types of saturated fat and their effects on HDL. Here, we’ll try to summarise that information, and highlight some interesting conclusions, in simpler language.

But first, a short chemistry lesson. Nothing too hard, hopefully – we’ll just focus on the main dietary saturated fats (technically, fatty acids), the 4 “even numbered, long-chain saturated fats”.

Lauric acid – a 12 carbon saturated fat (C12:0). This is the rarest of these 4 fats. It is mainly found in the diet in coconut oil (49% lauric acid) and dairy fat. Lauric acid also has some properties of  the shorter medium-chain fats (C6:0 – C:10:0), making it especially ketogenic.

Myristic acid – a 14 carbon saturated fat (C14:0). This is found in coconut oil, palm kernel oil, dairy fat, and the fats of ruminants and fish.

Palmitic acid – a 16 carbon saturated fat (C16:0). This is the most common of the saturated fats, and the second most common fat in nature after oleic acid (C18:1, a monounsaturated fat). It is found in all fats and oils.

Stearic acid – an 18 carbon saturated fat (C18:0). This is the second most common saturated fat, and is found in animal fats, cocoa butter, and palm oil.

The reality is that dietary fats, as they occur in actual foods, contain combinations of lots of different fatty acids; saturated, polyunsaturated, and monounsaturated. More, within each group they contain different combinations of each sort.

For example here’s what is in beef fat and butter*


These fats are also made in the body; they can be made from glucose and other sugars, and a shorter fat can also be converted to a longer one. Thus, palmitic acid (C16:0) is easily converted to both stearic acid (18:0) and oleic acid (18:1) in the carbohydrate fed state, myristic acid (C14:0) is less easily converted to palmitic acid (C16:0), and lauric acid (C12:0) is only with difficulty converted to myristic acid (C14:0).

The reason for these differences is that, the shorter the chain-length of a saturated fat, the quicker it is converted to energy (oxidised) and thus the less it is available for conversion to a longer fat (elongation).[1]


Dietary carbohydrate inhibits the oxidation of saturated fats and promotes their retention and elongation.[2]

This may explain why people eating low carbohydrate diets are able to eat a larger amount of energy from saturated fat without adverse effects – if indeed there are adverse effects to be experienced by saturated fats. Not only do all the blood markers of “cholesterol” improve (apart from rises in LDL cholesterol in a minority of cases), but the saturated fat content of the blood either decreases or, in a person where it was already low, stays the same.[3]

This is important because most of the health problems associated with saturated fat today are associated, not with saturated fat in the diet, but with a high level of saturated fat in the blood. High levels of palmitate and stearate are linked to insulin resistance, metabolic syndrome, and heart disease.[4,5,6] High levels of myristic acid and palmitate are linked to low levels of HDL and to NASH (non-alcoholic steatohepatitis), the inflammatory liver disease that is a dangerous consequence of NAFLD (non-alcoholic fatty liver disease).[7,8]
High plasma levels of palmitoleic acid (C:16:1 n-9), a rare monounsaturated fat formed when myristic acid is elongated to palmitate, are associated with increased future risk of new-onset type 2 diabetes.[9] This is a good indication that diets high in refined carbohydrate do play a causal role in this pathology, because levels of C16:1 drop once carbohydrate is restricted.[3]

When carbohydrate is restricted, and more fat including saturated fat eaten, the serum level of myristic acid falls more than that of palmitate, probably because its shorter chain-length means that its oxidation was less subject to carbohydrate control to begin with.[3]

It’s also the case that the shorter the chain length of a saturated fat, the more it raises HDL.[10]


And thus a very interesting set of correlations appears:

1: The shorter-chain the saturated fat, the faster it is converted to energy, and the harder it is to elongate.

2: The shorter-chain the saturated fat, the more it increases both HDL and LDL cholesterol at a normal carbohydrate intake.

3: The shorter-chain the saturated fat, the more the serum level in the blood drops when fat replaces carbohydrate

4: As a general rule, when fat replaces carbohydrate, both HDL, and the HDL: total cholesterol ratio, rise.


Mensink 2

Replacement of carbohydrate with a mixture of butter, coconut fat, olive oil and dark chocolate is predicted to improve the total to HDL cholesterol ratio

So, what is the connection? Well, it’s a mystery. So far, none of the references we’ve found actually indicates a mechanism by which some saturated fats raise HDL levels more than others.

We know that dietary fat (both saturated and monounsaturated) replacing carbohydrate increases the transport rate of ApoA-1 in liver cells, and that the decrease in triglyceride-rich VLDL with saturated fat in a low-carbohydrate diet, and the decrease in myristic acid levels, will help retain HDL in circulation long enough to do its job.[11,12]

(Interestingly, alcohol increases the transport rate of both ApoA-1 and ApoA-2, a type of HDL which has “no known function”, but which seems to be beneficial in moderate amounts, but to interfere with ApoA-1 function in larger amounts.)[13,14]
But we don’t yet have a mechanistic, nor an evolutionary, explanation as to why the chain-length of a C12-18 saturated fat and its rate of oxidation should make as much difference as it does to its effect on your HDL level. (Answers on a postcard please).

The bottom line: 
– all dietary fats are a mixture of saturated, monounsaturated, and polyunsaturated fats, and monounsaturated fat will make up the largest share of energy in the average low-carb diet (with the exception of coconut-based traditional diets), as it does in your body fat stores.
– It’s possible to eat a diet very high in lauric acid, but only if coconut or coconut oil is a major source of dietary energy. It’s impossible to eat a diet very high in myristic acid. These two fatty acids have the largest impact on HDL levels.
– Eating less carbohydrate will make less saturated fat appear in your blood between meals, even if you do eat more saturated fat, and this is most true for the lauric acid and myristic acid in your diet.
– There will also be benefits in terms of HDL (less) and reduced saturated fat in the blood (more)from a low-carb diet that is higher in monounsaturated fat, and lower in saturated fat than the average, if that’s what you like.

The bottom bottom  line: Don’t blame the butter for what the bread did!

*We have some evidence from New Zealand dairy fat expert Joycelyne Benatar that New Zealand dairy fat is, or was, higher in myristic acid than palmitic acid.[15,16] This is consistent with palmitic acid in milk being more the result of carbohydrate feeding (in grain-fed animals), or of animals being fed palm kernel expeller, and myristic acid being more the product of the synthesis of fatty acids from acetate supplied by fermentation.


[1] DeLany JP, Windhauser MM, Champagne CM, Bray GA. Differential oxidation of individual dietary fatty acids in humans. Am J Clin Nutr. 2000 Oct;72(4):905-11.

[2] Lossow WJ, Chaikoff IL. Carbohydrate sparing of fatty acid oxidation. I. The relation of fatty acid chain length to the degree of sparing. II. The mechanism by which carbohydrate spares the oxidation of palmitic acid. Arch Biochem Biophys. 1955; 57(1):23-40.

[3] Volk BM, Kunces LJ, Freidenreich DJ, et al. Effects of Step-Wise Increases in Dietary Carbohydrate on Circulating Saturated Fatty Acids and Palmitoleic Acid in Adults with Metabolic Syndrome. PLoS ONE. 2014;9(11):e113605. doi:10.1371/journal.pone.0113605.

[4] Sokolova M, Vinge LE, Alfsnes K, et al. Palmitate promotes inflammatory responses and cellular senescence in cardiac fibroblasts. Biochim Biophys Acta. 2017; 1862(2):234-245.

[5] Lu Z, Li Y, Brinson CW, Kirkwood KL, et al. CD36 is upregulated in mice with periodontitis and metabolic syndrome and involved in macrophage gene upregulation by palmitate. Oral Dis. 2016; Oct 18.

[6] Eulàlia Montell, Marco Turini, Mario Marotta et al. DAG accumulation from saturated fatty acids desensitizes insulin stimulation of glucose uptake in muscle cells. American Journal of Physiology – Endocrinology and Metabolism. 2001; 280(2): E229-E237.

[7] Tomita K, Teratani T, Yokoyama H et al. Plasma free myristic acid proportion is a predictor of nonalcoholic steatohepatitis. Dig Dis Sci. 2011 Oct;56(10):3045-52. doi: 10.1007/s10620-011-1712-0. Epub 2011 Apr 23.

[8] Martínez L, Torres S, Baulies A, et al. Myristic acid potentiates palmitic acid-induced lipotoxicity and steatohepatitis associated with lipodystrophy by sustaining de novo ceramide synthesis. Oncotarget. 2015;6(39):41479-41496.

[9] Mozaffarian D, Cao H, King IB. Circulating palmitoleic acid and risk of metabolic abnormalities and new-onset diabetes. Am J Clin Nutr 2010;92:1350–8. LINK

.[10] Mensink RP, Zock PL, Kester ADM, Katan MB. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr May 2003
vol. 77 no. 5 1146-1155.


[11] Brinton EA, Eisenberg S, Breslow JL. A Low-fat Diet Decreases High Density Lipoprotein (HDL) Cholesterol Levels by Decreasing HDL Apolipoprotein Transport Rates. J. Clin. Invest. 1990; 85: 144-151. 

[12] Noto, D et al. Myristic acid is associated to low plasma HDL cholesterol levels in a Mediterranean population and increases HDL catabolism by enhancing HDL particles trapping to cell surface proteoglycans in a liver hepatoma cell model. Atherosclerosis. 2016; 246:50 – 56.

[13] De Oliveira e Silva ER, Foster D, Harper MMcG, et al. Alcohol Consumption Raises HDL Cholesterol Levels by Increasing the Transport Rate of Apolipoproteins A-I and A-II.

[14] LW Castellani, Lusis AJ. ApoA-II Versus ApoA-I: Two for One Is Not Always a Good Deal. 

[15] Benatar JR, Stewart RAH. The effects of changing dairy intake on trans and saturated fatty acid levels- results from a randomized controlled study. Nutrition Journal. 2014; 13:32. LINK

[16] Palmitic acid increased from 15% to 30% of NZ dairy fat, and oleic acid increased from less than 10% to 30%, between 2011 and 2013, matching changes in palm kernel expeller use, at the expense of other saturated fats including myristic acid. Jocelyne Benatar quoted in Listener article by Jonathan Underhill, The Price of Palm Oil, 3 March 2017 LINK





Diet and HDL; the effect of myristic acid vs carbohydrate.


The nutrients that raise and lower HDL and ApoA1.

So is getting your HDL high a good thing?  It probably depends if you earned it or not…..and what you eat especially myristic acid

This very interesting study from 2014 brings into focus many of our recent posts about HDL, TG/HDL, ApoB/ApoA1 in the context of our more food-focused posts about butter and the dietary guidelines.[1]

This is a very readable paper which covers a lot of interesting ground.
It looks at the associations between reported intake of micronutrients and macronutrients and a variety of HDL-associated measurements (HDL, HDL-2, HDL-3, and ApoA1) in a case-control cohort (n=1566) selected for a study of coronary artery atherosclerotic disease (CAAD) – the CLEAR study.

The authors are coming off the back of a series of drug trials in which raising HDL had no benefit for CHD outcomes, and also the Mendelian randomisation research showing that genes associated with high HDL aren’t protective, whereas those associated with low LDL are.

The quick bottom line In our opinion this just means that HDL benefit isn’t a gift, but something you might need to work for through diet and exercise – especially keeping your insulin down. A low fasting TG/HDL ratio denotes low-normal insulin levels and the absence of insulin resistance, and that’s why higher HDL is protective against cardiovascular disease (because the higher triglyceride levels associated with insulin resistance on a high carb diet will force HDL down. Interestingly people sometimes get high TG and thus a high TG/HDL ratio when losing weight quickly, but this doesn’t seem to depress HDL).

(our post on the TG/HDL ratio)

The CLEAR study used the Harvard Food Frequency Questionnaire, so the amounts entered weren’t as exact as in feeding studies, but the authors have compared results to feeding studies where available and found the results are very consistent. To allow for inaccuracy of the method, the stronger correlations should be taken as more reliable, as well as more clinically meaningful. The FFQ analysis didn’t measure inessential or non-nutritive phytochemicals, so can’t tell us anything about their effects on HDL.


The strongest positive correlations with all HDL measurements were for myristic acid (C14 – a 14 carbon saturated fat) and alcohol, folate and magnesium were also associated with HDL, EPA (a fish omega 3) with HDL-2, and vitamin C with ApoA1, and fibre with HDL3 (the antioxidant form of HDL that may be most beneficial).[2]

The strongest negative association was with carbohydrate, and there were weak negative associations for iron and animal fat, as well as for arachidonic acid, the long-chain omega 6 found in animal foods, with HDL2.

The latter deserves an explanation – the sample was in a US population and in the US animal fat mainly comes from chicken, with some pork and other processed meats (that are usually associated with carbohydrate, e.g. on pizzas or in hotdogs). Chicken fat has almost no myristic acid or EPA, and is high in AA.

Myristic acid is 16% of coconut oil and palm kernel oil, 7-12% of butter fat, 2-4% of beef and lamb fat, 3% of salmon fat, 2% of lard, and less than 1% of chicken.

Other vegetable oils supply no myristic acid, including the palm oil that’s in junk food.
In a recent Listener article Otago professor Murray Skeaff stated that myristic acid is “far more cholesterol-raising than palmitic acid”. Be that as it may, and we will refrain from asking how much of that cholesterol-raising effect depends on HDL, we note than in every epidemiological study where different types of saturated fat have been measured in isolation, myristic acid has been associated with less harm , or more benefit, than palmitic acid or even stearic acid (which doesn’t raise LDL cholesterol).[3,4,5,6]

This difference is small and statistically insignificant, but it is always consistent, and doesn’t support a view that myristic acid is worse than other saturated fats.

As far as we can see, the main problem with myristic acid is that it can be elongated to palmitic acid by de novo lipogenesis when consumed in a high-carbohydrate diet.[7] The control of C16 and C18 levels by carbohydrate and insulin explains both the higher associations of these fats with disease (or lower protective associations in positive saturated fat studies) and the failure of low fat diets.[8] The rate of oxidation of saturated fats also depends on their chain length, thus C14 will be converted to energy faster than C16 – if fats are being oxidised.[9] This explains why MCT oil (which is mostly C8 and C10 saturated fats) is especially ketogenic. (the rate of oxidation of unsaturated fats, on the other hand, depends on their number of unsaturated bonds; the more they have, the faster they are oxidised and the more ketogenic they are).[9]


If we were designing a diet to raise HDL based on the CLEAR study, the diet would be low in carbohydrate, and its fat would supply myristic acid (not necessarily a very high amount – the CLEAR study subjects were average US dairy fat users) and EPA. Vegetables and fruit would also be encouraged as sources of magnesium, vitamin C, fibre, and folate. Salmon, eggs, and dairy, as foods supplying desirable fats, would replace some of the red meats supplying iron (avoiding processed grains would also reduce the iron content of the diet – note though that the iron correlation, though consistent with other evidence, is not very strong; and that lamb supplies appreciable amounts of EPA).
The animal fat correlation was weak, and the authors didn’t bother to explain it or treat it as meaningful, probably due to a lack of supporting evidence. It is almost certain to be due to confounding from the Harvard FFQ program and the US diet, where animal fats are found together with processed carbohydrate foods. The omega-3/6 balance of animal foods was strongly correlated with HDL2; linoleic acid wasn’t included in the analysis because it correlated too strongly with other dietary fats to be isolated, but ALA (omega-3) was and wasn’t associated with HDL.

Although whole grains are a source of folate, and folic acid is added to most bread today (and to white rice in the USA), iron is also added to refined grains. Legumes supply more folate by weight and per carbohydrate calorie than whole grains, as well as more magnesium and fibre. Organ meats and leafy green vegetables are also good sources of folate.

Interestingly alcohol was dose-dependently correlated with HDL and ApoA1, supported by the cardioprotective associations of moderate drinking. However, there were only a few (21) heavy drinkers (>60g day) in the sample. Because heavy drinking is associated with cancer, accidental death, and heart failure, and is very likely to make you and everybody else miserable in the long run, we don’t recommend this approach to HDL-raising, except for people who already enjoy alcohol in moderation (defined as 10-30g/day, that’s 1 or 2 small glasses of wine or standard drinks).

However, the protective associations between moderate alcohol consumption and CHD clearly show that not every drug that elevates HDL fails to reduce risk. Of course, alcohol is also a food, which might help. Note that, if you do drink, the types of fat that supply most myristic acid in the diet – coconut oil, dairy fat, and beef and lamb dripping – are (along with cocoa butter) those that are most protective against alcoholic liver disease.[10]

Myristic acid raises HDL and LDL cholesterol

Where does the idea that myristic acid is harmful come from? This feeding study showed that myristic acid raised cholesterol, both HDL and LDL – however, to get this amount of myristic acid, 11% of diet, which was supplied by a special 50% myristic acid margarine, from ordinary foods, you would have to eat nothing but butter. Carbohydrate intake in the study was 47% of energy, fat was 39%.[11]

Myristic acid is the third most common saturated fat in the diet. Average intake levels are about 1 g/d in Japan, 6 g/d in the United States, 8 g/d in the Netherlands, and 14 g/d in eastern Finland (D. Kromhout et al, unpublished data, 1988). Major sources are butter fat, which is also rich in palmitic acid, and two vegetable oils, coconut oil and palm kernel oil; the latter two also contain large amounts of lauric acid. Palm oil, another vegetable oil that is high in saturated fatty acids, is low in myristic acid and high in palmitic acid. Palm oil is the number one edible oil worldwide, and its consumption is rising. If much of the cholesterol-raising effect of saturated fatty acids is indeed specifically due to myristic acid, then palm oil would be a suitable substitute for animal fats and hydrogenated vegetable oils in a wide range of products for cholesterol-lowering diets. Moreover, modern biotechnology could be applied to replace myristic acid with palmitic acid in other fats.

The diet, not mentioned in that study, with the most myristic acid – over 20g/day – would have been that of the Tokelau islanders who got most of their energy from coconuts, had a high percentage of myristic acid in adipose tissue (4x that of Europeans) and had very low rates of cardiovascular disease – on a lower carbohydrate diet. [12]

Carbohydrate controls the HDL response to Myristic acid

What happens to myristic acid on a low carb diet? This study by Jeff Volek et al measured fatty acids in the blood on a 1500 kcal 12% carbohydrate diet (about 50g carbohydrate), compared with a 1500 kcal low fat diet (24% fat, 56% carbohydrate).[13]
(This initial finding was supported by a series of other experiments by this group, including one in which a dose-response effect of carbohydrate on serum C14 levels was demonstrated, and another in which the effect was shown in the absence of calorie restriction or weight loss.)[8,14]

The dietary intake of saturated fat was threefold higher on the CRD (36 g/day) compared to the LFD (12 g/day). Remarkably, the CRD showed consistently greater reductions in the relative proportions of most circulating SFAs in TAG and CE fractions (16), mainly attributed to greater reductions in myristic (14:0; 47% reduction) and palmitic (16:0; 10%) acids. With the exception of those with a low level at baseline, nearly all subjects consuming the CRD had a decrease in total saturates (17 of 20 subjects), whereas only half the subjects consuming the LFD had a decrease in saturates. Taking into account the change in absolute fasting TAG levels, the absolute concentration of total saturates in plasma TAG was reduced by 57% in response to the CRD, compared to 24% in response to the LFD.

Thus we see that, as we would expect, myristic acid in the blood is decreased by carbohydrate restriction faster than longer-chain saturated fats. HDL of course increased in the low-carb arm; which is consistent with this study showing that higher myristic acid in the blood (not diet) of a Mediterranean population is associated with lower HDL.[15] This paper also cites Mensink et al “a large meta-analysis including 60 dietary intervention studies concluded that the increase of HDL-C due to SFA progressively decreases with the elongation of the acyl chain, being maximal for C12:0 (lauric acid) and not relevant for C18:0” – so the faster beta-oxidation of myristic acid (and lauric acid, not isolated in the CLEAR study) correlates with the greater rise in HDL.

And if myristic acid isn’t oxidised, because the carbohydrate content of the diet is too high for the insulin sensitivity of the individual – carbohydrate intolerance – HDL can go down instead.

The following human study also shows that myristic acid modulates omega 3 status;[16]

In addition, in humans, compared with a diet containing 0.6% of myristic acid mainly in the sn-2 position in the TAG [i.e. dairy fat], a diet containing 1.2% of myristic acid during a 5-week consumption period significantly enhanced EPA and DHA levels in the plasma PL and DHA level in the plasma cholesteryl esters [60]. When the intake of myristic acid increased from 1.2 to 1.8% energy in the same population, EPA, DPA and DHA decreased significantly in plasma PL and EPA also decreased in cholesteryl esters [61]. This result suggest that, in humans, the effect of myristic acid on circulating (n-3) PUFA follows a U-shaped curve with a favorable turning point at around 1.2% of total daily energy.

1.2% of dietary energy would be equal to 10-12% of energy from dairy fat. But note that this was in the context of a high carb diet, and that it’s likely this threshold would increase as the rate of myristic acid oxidation increased at lower carbohydrate intakes.

In low-fat diets, it looks like there’s an optimal amount of myristic acid, which you’d get by including full fat dairy foods, as shown by the DASH diet study of Chiu et al (increasing saturated fat from animal foods over baseline improves biomarkers in people eating a supposedly “healthy” diet pattern).[17] The omega-3 study we cited above, and the Med diet serum HDL study, show that in low-fat diets or in carbohydrate intolerant individuals there’s a limit to benefit – a U shaped curve. Putting lots of butter on white bread with jam, or in sweet cakes, as Kiwis did in the 1960’s, you can maybe come off that curve and prang badly. But once you look at lower carb diets, it looks as if myristic acid is a fat that’s well tolerated, doesn’t hang around, and is easy to benefit from (remember, at around 16% of coconut oil, 10% of dairy fat, much lower amounts in other animal fats, and almost none in olive oil and nuts, it’s unlikely to be a major type of fat in the average low carb diet).

The PURE study
And, to turn to the famous PURE study, also a case-control study but a very large one with dietary intakes and lipids stratified into quintiles,
“higher carbohydrates intake has the most adverse effect on lipid profiles and replacing it with saturated fat improved HDL and TG and replacing it with MUFA improved TC/HDL-C and ApoA/ApoB.”[18]

ApoB/ApoA was the lipid marker chosen as the best risk predictor in PURE and the INTERHEART study. Animal fats are predominantly mixtures of saturated fat and MUFA.
We discussed the reasons why using ApoB/ApoA1 predicts that there will be cardiovascular benefits of carbohydrate restriction in this post.

Looking at the evidence around myristic acid shows us, once again, that carbohydrate drives the pathologies fat gets blamed for.
And it shows us, once again, that judging foods based on their effects on cholesterol and LDL as if this was the only game in town has been a huge blunder in terms of public health.

If you erroneously think that replacing fat with carbohydrate, because this will lower cholesterol, is the key to health, and find out this doesn’t work, then restricting certain kinds of fat becomes a logical, but largely ineffective,  and sometimes counterproductive, follow-up part of your strategy.

You can even end up thinking that it’s okay that palm oil is overtaking butter in the NZ diet. Not that there’s much evidence that it’s harmful yet, except to orangutans, but surely, it’s just unnecessary, and takes us further away from eating real foods that could be produced at home, and deeper into the hands of a global food industry that hasn’t really looked after our interests so far.


[1] Kim et al. “Effects of dietary components on high-density lipoprotein measures in a cohort of 1,566 participants.” Nutrition & Metabolism 2014, 11:44.

[2] Kim DS, Burt AA, Rosenthal EA, et al. HDL‐3 is a Superior Predictor of Carotid Artery Disease in a Case‐Control Cohort of 1725 Participants. Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease. 2014;3(3):e000902. doi:10.1161/JAHA.114.000902.

[3] Zong Geng, Li Yanping, Wanders Anne J, Alssema Marjan, Zock Peter L, Willett Walter C et al. Intake of individual saturated fatty acids and risk of coronary heart disease in US men and women: two prospective longitudinal cohort studies BMJ 2016; 355 :i5796.

[4] Ericson, U, Hellstrand, S, Brunkwall, L, Schulz, C-A, Sonestedt, E, Wallström, P, et al. Food sources of fat may clarify the inconsistent role of dietary fat intake for incidence of type 2 diabetes. AJCN 2015;114.103010v1

[5] Praagman J, Beulens JW, Alssema M, et al. The association between dietary saturated fatty acids and ischemic heart disease depends on the type and source of fatty acid in the European Prospective Investigation into Cancer and Nutrition-Netherlands cohort. Am J Clin Nutr2016;103:356-65.

[6] Praagman J, de Jonge EA, Kiefte-de Jong JC, Beulens JW, Sluijs I, Schoufour JD, et al. Dietary Saturated Fatty Acids and Coronary Heart Disease Risk in a Dutch Middle-Aged and Elderly Population. Arterioscler Thromb Vasc Biol. 2016; 36(9): 2011-8.

[7] Lossow WJ, Chaikoff IL. Carbohydrate sparing of fatty acid oxidation. I. The relation of fatty acid chain length to the degree of sparing. II. The mechanism by which carbohydrate spares the oxidation of palmitic acid. Arch Biochem Biophys. 1955; 57(1):23-40.

[8] Volk BM, Kunces LJ, Freidenreich DJ, et al. Effects of Step-Wise Increases in Dietary Carbohydrate on Circulating Saturated Fatty Acids and Palmitoleic Acid in Adults with Metabolic Syndrome. PLoS ONE. 2014;9(11):e113605. doi:10.1371/journal.pone.0113605.

[9] DeLany, JP, Windhauser, MW, Champagne, CM, Bray, GA. Differential oxidation of individual dietary fatty acids in humans. Am J Clin Nutr October 2000;72(4):  905-911

[10] Kirpich IA, Miller ME, Cave MC, Joshi-Barve S, McClain CJ. Alcoholic Liver Disease: Update on the Role of Dietary Fat. Osna N, Kharbanda K, eds. Biomolecules. 2016;6(1):1.

[11] Zock PL, de Vries JH, Katan MB: Impact of myristic acid versus palmitic
acid on serum lipid and lipoprotein levels in healthy women and men.
Arterioscler Thromb Vasc Biol 1994, 14:567–575.

[12]Prior IA, Davidson F, Salmond CE, Czochanska Z. Cholesterol, coconuts, and diet on Polynesian atolls: a natural experiment: the Pukapuka and Tokelau island studies. Am J Clin Nutr. 1981; (34)8: 1552-1561.

[13] Volek JS, Phinney SD, Forsythe CE et al. Carbohydrate restriction has a more favorable impact on the metabolic syndrome than a low fat diet. Lipids. 2009;44(4):297-309. doi: 10.1007/s11745-008-3274-2. Epub 2008 Dec 12.

[14] Forsythe CE, Phinney SD, Feinman RD et al. Limited effect of dietary saturated fat on plasma saturated fat in the context of a low carbohydrate diet. Lipids. 2010; 45(10):947-62. doi: 10.1007/s11745-010-3467-3. Epub 2010 Sep 7.

[15] Noto, D et al. Myristic acid is associated to low plasma HDL cholesterol levels in a Mediterranean population and increases HDL catabolism by enhancing HDL particles trapping to cell surface proteoglycans in a liver hepatoma cell model. Atherosclerosis. 2016; 246:50 – 56

[16] Legrand P, Rioux V. The Complex and Important Cellular and Metabolic Functions of Saturated Fatty Acids. Lipids. 2010;45(10):941-946. doi:10.1007/s11745-010-3444-x.

[17] Chiu S, Bergeron N, Williams PT, Bray GA, Sutherland B, Krauss RM. Comparison of the DASH (Dietary Approaches to Stop Hypertension) diet and a higher-fat DASH diet on blood pressure and lipids and lipoproteins: a randomized controlled trial. Am J Clin Nutr. 2015. ajcn123281.

[18] Dehghan M, Anand S, Mente A, Yusuf S on behalf of PURE study working group. OC06_01 Association of Nutrients With Blood Lipids in 19 Countries and 5 Continents: The Pure Study. Global Heart. 2016; (11)2: e6.



Dietary Guidelines – our letter in The Lancet

If anyone’s interested in the public health nutrition debate around the dietary guidelines, then here’s a summary and critique of our latest jousting round(s) with conventional wisdom.

In late 2016, an article from New Zealand in defense of the current dietary guidelines was published in the renowned medical journal The Lancet. While the authors (who included Prof Jim Mann, Dr Lisa Te Morenga, Prof Rod Jackson, and Prof Boyd Swinburn) ranged far and wide over the justifications for current guidelines, they cited no research critical of them, and ignored the most trenchant criticisms, which allowing them to exaggerate the importance of the evidence that it suited them to address.

An example of their straw man approach is here:
“But the case for reducing carbohydrate in general centres on whether there are benefits associated with reduction of starches and non-starch polysaccharides.”


There’s plenty of fibre in a Straw Man.

Non-starch polysaccharides are, in general, what we call fibre. Yet there is no case being made for a weight loss benefit from reducing fibres that we have ever seen (di- and mono-saccharides, or sugars, would be the correct term to include instead). This seems like a rather childish game – “if you’re restricting carbohydrate you must be restricting fibre too, because that’s a carbohydrate”. It also betrays a poor awareness of food composition – a low carbohydrate fruit or vegetable will have more fibre per calorie than a high carbohydrate food.

They claim that dietary guidelines now include a high-fat diet; “a high-fat, high-carbohydrate Mediterranean diet, which is associated with a fairly low risk of many NCDs” but this is about 40% fat. This definition of high fat allows them to make the claim that “Meta-analyses of trials in people not attempting to lose weight show moderately lower bodyweight loss among those on diets fairly low in fat (30% or less total energy) than those on carbohydrate-reduced higher fat diets.”

But in fact not one of the control arms in those studies was “carbohydrate-reduced” in a medical sense, except for the fact that they were a little higher-fat than the interventions, merely representing the normal diets of their day, replete with white flour, partially hydrogenated oils, and sweets. Food quality is an important confounder in diet trials, and in most of the old low-fat and saturated-fat reduced studies the intervention groups were told to eat nuts and fish, whole grains, fruits and veges, and cut back on sugar, flour, and foods made with hydrogenated shortening, making it hard to attribute any benefits to increased carbohydrate or polyunsaturated vegetable oil.

The article re-iterated claims that saturated fat should be replaced with polyunsaturated fat, then stated that pitting one macronutrient against another risks confusing the public.

But what is wrong with telling everyone to eat healthy higher-carb diets?

There are three main problems that we can see:
Firstly, and most importantly, a large, and growing, proportion of the population is carbohydrate-intolerant. They have obesity, metabolic syndrome, excessive TG/HDL ratio, rising HbA1c, if not frank diabetes, and restricting carbohydrate is the most effective way to reverse this cluster of chronic disease associated with hyperinsulinaemia, which is increasing their odds of dying young from heart disease, cancer, diabetic complications and so on. Let us also be clear – carbohydrate intolerant means that these people have difficulty of disposing of dietary carbohydrates without advert metabolic effects of high triglycerides, high blood glucose and hyperinsulinemia.

Secondly, there is no evidence that full-fat dairy is anything but beneficial compared to low-fat (and there’s very little evidence comparing lean and fatty meats). If dairy fat, the most saturated animal fat in existence, doesn’t cause heart disease, then the basis for saturated fat restriction is very weak. There may be benefits from optimal intakes of certain polyunsaturated fats, but there’s no evidence that oils are the best source of these fats, nor that replacing other fats (which will always tend to limit the percentage of fat in the diet) is essential for benefit.

Thirdly, this “virtuous” diet advice might disadvantage the poor. Fat-free milk or (plain) yoghurt is the same price as full-fat milk or yoghurt, yet supplies half as much energy and fewer vitamins. Nuts, fish, and lean meat are more expensive per calorie than cheese, fatty cuts, and eggs. Light coconut cream, cream cheese, or sour cream is the same price as full-fat. If someone makes these low-fat choices, they need more energy from other sources (i.e. are left hungry), but have less money left to ensure its quality. Fruit and vegetables are relatively expensive, and a good whole grain bread costs about four or five times as much as white bread.

We tried to unpick some of these contradictions in a letter to the Lancet, which that journal was gracious enough to publish last week.

Dietary guidelines are not beyond criticism

Mann and colleagues (Aug 27, p 851) claim that criticisms of the dietary guidelines are not evidence-based.[1] However, even by their own account, the promotion of reduced-fat dairy products in existing guidelines is not evidence-based, in view of the lack of association of dairy fat with cardiovascular risk, and the strong protective associations that exist between ruminant fatty acids and type 2 diabetes.[2] This evidence contradicts the theory that the effect of dietary saturated fat on serum cholesterol is the cause of the association between serum cholesterol and cardiovascular disease.

Carbohydrate intolerance is increasing in developed and developing countries, as indicated by growing rates of diabetes, obesity, and metabolic syndrome, with the consequent expansion of health costs. Evidence is emerging that a major nutritional cause of modern chronic disease is the glycaemic environment created by the interaction between insulin resistance and foods with a high glycaemic load (GL), increased consumption of which has been a natural consequence of advice to limit dietary fat.[3]

Mann and colleagues cited two meta-analyses [4,5] excluding weight loss trials, in which low-fat diets were only compared with low quality, high GL control diets. However, in view of the disappointing results in most trials in which a low-fat diet has been compared with alternative dietary interventions, the evidence is unclear on whether a fat-restricted bias in dietary advice is justified.[6] Population dietary guidelines should be adapted to include advice on carbohydrate restriction, which is likely to be beneficial or protective for a large, but growing, proportion of people.

[References are in link]

That’s all. Seems uncontroversial enough right? What we’re saying is that some people do well with low carb advice, and there are today more than enough people in this category to justify including it as an option in dietary guidelines. We’re also saying that the evidence for fat restriction is not so strong that it needs to be a barrier to low carb diets, nor to good nutrition in general.

We weren’t just trolling (or The Lancet wouldn’t have published our letter – The Lancet is harder to get into than the Auckland housing market). We really hoped to be having a discussion about how the low carb idea can be incorporated into guidelines for the people who need it. The UK’s Public Health Coalition showed how this can be done last year, and we started the ball rolling with our own Real Food Guidelines in 2014.
But instead Mann et al. doubled down on their claims.

In particular, they pretended not to understand the idea of carbohydrate intolerance.

We find the link proposed by Henderson and colleagues between “carbohydrate intolerance” and “diabetes, obesity, and metabolic syndrome” puzzling. Carbohydrate intolerance is characterised by abnormal carbohydrate digestion as in lactose intolerance, and is not associated with abnormalities of glucose metabolism.

This from the people who think that carbohydrate restriction means fibre restriction.

Their new justification for low-fat dairy is interesting.

Low-fat, as opposed to full-fat, dairy products are generally recommended to promote consumption of essential nutrients and to allow intakes of food sources of unsaturated fatty acids without promoting excess energy intake.

Basically, we’ve been telling you to eat low-fat dairy so we can feed you extra oil without making you fat. Well guess what people, it’s not working and there is no “totality of evidence” as you always call it for this. In fact, such a body of evidence just doesn’t exist.

This passage makes a point which is not without substance, but deserves further comment:

However, we are unaware of any deleterious effects of minimally processed wholegrains or fibre-rich intact vegetables (notably legumes and pulses) and fruits—which are protective against diabetes, useful in its management, and with additional benefits in terms of cardiovascular and gastrointestinal disease.

On reading this reply, Nina Teicholz, author of The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet, which is an engrossing and indeed exciting (and deservedly best-selling) history of how the low-fat idea became embedded in official advice despite the continual appearance of evidence to contradict it, wrote a detailed response on PubPeer, which is a post-publication peer-review website.

Iterating a claim made in their initial Comment, the authors again assert that there is a “substantial body of observational, clinical trail, and experimental evidence…[to] support the recommendation to reduce total saturated fatty acids and that they might be replaced with unsaturated vegetable oils.” However, this body of evidence does not exist. There is now a total of at least 17 systematic reviews and meta-analyses looking at the totality of the evidence on saturated fats (1) which have largely concluded that saturated fats have no association with nor any effect on cardiovascular or total mortality.

Furthermore, the authors did not, as they state, summarize the above evidence in their original Comment. Instead, they chose a small selection of the evidence, which they then misrepresented to support their claims about saturated fat. I wrote about this when their Comment was first published (2).

The authors write that this body of evidence “does not negate advice to reduce total saturated fat,” but if a large body of rigorous, government-funded, randomized controlled trials testing saturated fats on more than 50,000 people have found no effect of saturated fats on cardiovascular mortality, then this does indeed negate advice to reduce total saturated fat.

The authors further write that they are “unaware of any deleterious effects of minimally processed whole grains or fibre-rich intact vegetables (notably legumes and pulses) and fruits. If so, then the authors are unaware of the large body of clinical trial research demonstrating that reducing total carbohydrate intake is highly effective for managing or even reversing obesity and diabetes. Thus, for people who are struggling with weight or diabetes, the high-carbohydrate foods listed above might be enjoyed in small amounts, but taken together as a majority of one’s diet, these foods would constitute a high-carbohydrate diet–which has been shown to be entirely ineffective, if not actually detrimental, in fighting these diseases.

That the authors characterize “carbohydrate intolerance” as “lactose intolerance” suggests that they have not read the literature on the effect of glucose and fructose on insulin, fat deposition, fatty liver disease and adverse lipid effects. This large body of literature describes the body’s unique metabolic response to carbohydrates, compared to other macronutrients. It seems uncharitable for the authors to accuse their critics of being engaged in a “continuing attempt to pit one macronutrient against another.” Science is not politics–or at least shouldn’t be. No one is “pitting” macronutrients against each other, like Hillary vs. Trump. Rather, researchers who discuss the observations that the body has a differing metabolic response to different macronutrients are simply following the duty of any scientist: to respond and explain the observations. If their explanation can be countered by a more convincing one, then that’s where a good scientific exchange could take place. Debate over science should be allowed to happen. To accuse researchers who disagree with them of seeking only to “perpetuate confusion,” as the authors write, appears merely to be an attempt to shut down legitimate debate.

Finally, it is untrue that “existing population-based dietary guidelines permit a wide range of macronutrient intake.” In the US, the three suggested “Dietary Patterns” are all modeled at more than 50% carbohydrates (3), which, by any definition, cannot be considered a low-carbohydrate diet.


People who say that carbohydrate restriction means fibre restriction, that carbohydrate intolerance can only mean lactose intolerance, and that 50% carbohydrate diets are the high fat extreme of a wide range of macronutrient intakes, should not accuse others of perpetuating confusion.

I (GH) added a bit of detail below Nina’s PubPeer comment about the circumstances under which fruit and wholegrains appear beneficial for diabetes prevention in epidemiological studies – the amount of carbohydrate from these foods associated with greatest benefit is actually minimal and would fit in most low carb diets.

We wrote another letter in response to Mann et al’s author reply, but as it is unlikely that The Lancet will keep a correspondence going over such a long period, we will post it here.

Dietary Guidelines are already confused.

The position that Mann et al propose be taken towards full-fat dairy foods, to await the results of further research into their benefits, is the opposite of what a public health nutrition approach should be. Nutritious, popular, and traditional foods should never have been advised against until after such research was completed. Advice to use unsaturated oils instead has been based on population studies that did not differentiate adequately between oils and wholefoods as sources of unsaturated fat, except in the case of olive oil, a traditional fat, and the olive oil studies have not shown that the avoidance of full-fat dairy or meat is required for benefit.[1,2]

Semantic quibbles about carbohydrate intolerance are inappropriate – most readers of the Lancet are familiar with the uses of the oral glucose tolerance test, and many will also be familiar with the importance of the fasting TG/HDL ratio, fasting insulin, or two-hour insulin response in predicting the future risk of chronic disease.[3] These are measurements which, if abnormal, will be more sensitive to the ingestion of carbohydrate than of other nutrients.[4, 5] Carbohydrate intolerance is thus a simple formula allowing the public to understand a concept of considerable importance in public health.

Advice to use low-fat or lean versions of traditional foods, in part because of the outdated notion that eating the whole-fat versions of these foods leads to excess energy intake, does not in practice allow a wide range of macronutrient intakes. Instead we propose that it would help to reverse the burden of chronic disease to acknowledge the benefit for some of replacing foods rich in starch or sugar with less carbohydrate-dense whole foods. When conditions such as obesity, type 2 diabetes, and the metabolic syndrome are as widespread as they are today, it is remiss not to include those simple instructions most likely to assist with their reversal in public health diet advice.

[1] Buckland G, Mayen AL, Agudo A, et al. Olive oil intake and mortality within the Spanish population (EPIC-Spain). Am J Clin Nutr. 2012; 96: 142-149.

[2] Guasch-Ferré M, Babio N, Martínez-González MA, Corella D et al. Dietary fat intake and risk of cardiovascular disease and all-cause mortality in a population at high risk of cardiovascular disease. Am J Clin Nutr. 2015; 102(6):1563-73. doi: 10.3945/ajcn.115.116046.

[3] Temelkova-Kurktschiev T, Henkel E, Schaper F et al. Prevalence and atherosclerosis risk in different types of non-diabetic hyperglycemia. Is mild hyperglycemia an underestimated evil? Exp Clin Endocrinol Diabetes 2000; Vol. 108(2): 93-99.

[4] Volek JS, Feinman RD. Carbohydrate restriction improves the features of Metabolic Syndrome. Metabolic Syndrome may be defined by the response to carbohydrate restriction. Nutrition & Metabolism. 2005; 2:31.

[5] McKenzie MR, Illingworth S. Should a Low Carbohydrate Diet be Recommended for Diabetes Management? Proceedings of the Nutrition Society. 2017; 76 (OCE1), E19



Margarines, Cooking Oils, and Non-dairy Spreads – is there enough evidence for benefit or harm?


How much evidence do you need to make recommendations about what the public should eat?

It depends really.

“On fair evidence we might take action on what appears to be an occupational hazard. For example, we might change from a probably carcinogenic oil to a non-carcinogenic oil in a limited environment and without too much injustice if we are wrong. But we should need very strong evidence before we made people burn a fuel in their homes that they do not like or stop smoking the cigarettes and eating the fats and sugar that they do like.”

This a quote from a great framework used in public health for making such decisions. It was put forward by Austin Bradford Hill in the 1960s, and has become known as the “Bradford Hill criteria“. It’s a set of conditions that should be met, or tests that should be made, before public health people start to make recommendations about what to avoid and what to do instead.

See also, Austin Bradford Hill, “The Environment and Disease: Association or Causation?”
Proceedings of the Royal Society of Medicine, 58 (1965), 295-300.

So what does this have to do with margarine?

In the previous post, we learned that New Zealanders on average consume around 4.9Kg of butter per capita each year, as well as a similar amount of palm oil, around 8.5Kg of canola oil, and around 2.7Kg of soy bean oil (a total of 21Kg of added fat, similar to the totality of 1966 butter intake). Much of the latter three oils goes into non-dairy spreads (along with smaller amounts of other oils such as corn, olive, rice bran, and sunflower, figures for which were not available). So what do we know about these oils and spreads, and their health effects, and should we be telling people to eat them especially over butter?

What are non-dairy spreads?

Butter is butter; its composition will vary slightly depending on what the animal is fed, so that winter silage produces a paler fat, lower in carotenoids, and the feeding of palm kernel expeller produces a fat in which the beneficial trans, cis fat rumenic acid (or CLA) is partly replaced by other trans fats, the importance of which is still uncertain, but these differences are very small compared to the differences that exist within the categories of margarine and non-dairy spreads. Although we’ll use the terms interchangeably here, food labelled “margarine” (a word few food producers seem to use today), as chemist Laurence Eyres reminded us in the Listener, must by law contain at least 80% fat, whereas spreads are usually lower fat. What Eyres doesn’t tell us is that this can be animal fat – there are budget spreads in the supermarket that contain beef fat as an ingredient. Not that there’s anything wrong with that, but obviously the idea that we can “replace animal fat with non-dairy spreads” is a bit misleading.

It’s curious that no-one who supports the substitution of margarine for butter mentions this, and the reason may be that the substitution exists in their heads as a theoretical one – they don’t actually go down to the supermarket and read the labels on the different products that people are buying and eating, or if they do, they only read the saturated fat information on the label.

A lot is made of the use of partially hydrogenated oils (PHO), a source of trans fats, in margarine, and how these are being removed from the food supply by a voluntary arrangement, with labeling still optional. Other countries have made greater efforts to label and remove industrial trans fats than New Zealand, Australia, and the UK. India introduced mandatory labelling and limits on trans fats from PHO within a short period, and the US FDA withdrew the GRAS (generally recognized as safe) classification from PHO, with a complete ban (barring any exemptions being granted) effective later this year. Note that other sources of saturated fats, and of naturally occurring trans fats, are still GRAS and always will be, so that attempts to combine “trans fat and saturated fats” into some common category of “bad fats” have no validity. But why was PHO included in margarine to begin with?

Butter has a spreadable consistency (at least at the right temperature), partly because its saturated fat content ensures that it is not too runny, and partly because the phospholipids and cholesterol it contains allow the fats to form an emulsion with its small amount of water. The trans fats in PHO were straight chains like saturated fats, so had a similar consistency, while appearing as unsaturated fats when tested in the laboratory (they also, unlike saturated fats, interfered with the conversion of polyunsaturated fats into various signaling molecules, which was a bad thing). So they have had to be replaced with more saturated fats, such as beef fat or palm oil. Lighter spreads that don’t contain these fats need to include emulsifiers and stabilizers; this gives them more in common with other highly processed foods, and also means that you’re paying extra for water. The technology of interesterification means that oils can now be made harder by switching fatty acids around on the glycerol backbone of triglycerides, changing their interactions with one another and thus their consistency, but this technology is only used in some of the spreads on the NZ market.

Vegetable spreads – what evidence is there for benefit?

So is there anything (causally) harmful or good about these products? Do they have health benefits? Bearing in mind the Bradford Hill criteria which look at the scientific evidence. The evidence should be tested against these criteria:

  1. Strength (effect size): A small association does not mean that there is not a causal effect, though the larger the association, the more likely that it is causal.
  2. Consistency (reproducibility): Consistent findings observed by different persons in different places with different samples strengthens the likelihood of an effect.
  3. Specificity: Causation is likely if there is a very specific population at a specific site and disease with no other likely explanation. The more specific an association between a factor and an effect is, the bigger the probability of a causal relationship.
  4. Temporality: The effect has to occur after the cause (and if there is an expected delay between the cause and expected effect, then the effect must occur after that delay).
  5. Biological gradient: Greater exposure should generally lead to greater incidence of the effect. However, in some cases, the mere presence of the factor can trigger the effect. In other cases, an inverse proportion is observed: greater exposure leads to lower incidence.
  6. Plausibility: A plausible mechanism between cause and effect is helpful (but Hill noted that knowledge of the mechanism is limited by current knowledge).
  7. Coherence: Coherence between epidemiological and laboratory findings increases the likelihood of an effect. However, Hill noted that “… lack of such [laboratory] evidence cannot nullify the epidemiological effect on associations”.
  8. Experiment: “Occasionally it is possible to appeal to experimental evidence”.
  9. Analogy: The effect of similar factors may be considered.

Criteria 1 and 2: Strength and consistency of epidemiological evidence

There is a body of epidemiological research that claims that replacing saturated fat (or carbohydrate) with polyunsaturated fat reduces cardiovascular risk. Unfortunately, the association isn’t consistent (there are populations where no association, or the opposite association has been seen, at least from theoretically replacing saturated fat with polyunsaturated fat).[1, 2] However, even in the populations where this association has been seen, there’s no clear evidence that margarine, or cooking oil, is the source of it. The problem is that many minimally refined foods are also good sources of polyunsaturated fat, especially chicken and pork, nuts and seeds, olives and avocadoes, but also meat and dairy; all whole foods add more polyunsaturated fat to the diet than sugar and flour do. There don’t seem to have been many attempts to isolate the polyunsaturated fat in oils and spreads and compare it with that in whole foods and animal fats.

There have only been a few epidemiological studies comparing margarine with butter. In Framingham, which was the original large population followed to test the lipid hypothesis (it didn’t work out – there was never any neat linear association between saturated fat in the diet, LDL cholesterol, and heart disease), using margarine instead of butter was associated with no change in heart disease during the first 10 years, then an increase over the 10 years following.[3] This was attributed to trans fats, but that doesn’t explain the different effects over 10 and 20 years.

“Adjusted for age and energy intake, the risk ratio for CHD for each increment of 1 teaspoon per day of margarine was 0.98 [95% confidence interval (CI) = 0.91-1.05] for the first 10 years of follow-up and 1.10 (95% CI = 1.04-1.17) for follow-up years 11-21. Butter intake did not predict CHD incidence.”

Recently, a study was published claiming a theoretical benefit from margarine use instead of butter for heart attack (MI) risk over a 13 year period.[4]
“Substituting butter or stick margarine with tub margarine was associated with lower risk of MI (HRs = 0.95 and 0.91). Subgroup analyses, which evaluated these substitutions among participants with a single source of spreadable fat, showed stronger associations for MI (HRs = 0.92 and 0.87). Outcomes of total CHD, ischemic stroke, and atherosclerosis-related CVD showed wide confidence intervals but the same trends as the MI results.”

Unfortunately, this study is one we don’t have access to, and the methods are not obvious; however, no number of events is given in the abstract, so it is possible that “theoretical” just means calculated risk from serum lipids. Still, it’s noticeable that even in this study, substituting one type of margarine for another was associated with more benefit than replacing butter.

(Given the variety of non-dairy spreads on the market, and the inconsistency of their ingredients, it might be more helpful if the experts fought over what sort of margarine people should use, rather than whether they should use it instead of butter).
There may be other evidence that using margarine, specifically, is associated with beneficial outcomes, but if so we haven’t been able to find it.

Criteria 4 and 6: Temporality and Biological plausibility

What about oils? There’s an interesting paper from the Nurse’s Health Study that looked at two different sources of the omega 3 fat ALA.[5] A higher consumption of ALA from (soy) oil-and-vinegar salad dressing was associated with a lower risk of fatal heart attacks, RR 0.46 (0.27, 0.76), whereas a higher consumption of mayonnaise was not, RR 0.84 (0.50, 1.44). Yet mayonnaise is the richer food and contributed more ALA to diets than oil-and-vinegar salad dressing (16.7% vs 12.2%). This study didn’t look at intake of margarine as a source of ALA (6.8%). A relevant point is that much of this population was probably deficient in omega-3 fats (American’s don’t eat much fish, and median daily energy-adjusted ALA intake ranged from 0.71 g in the lowest quintile to 1.36 g in the highest quintile), so we are probably looking at the effects of correcting a deficiency of an essential nutrient. Of course, if you’re using lots of oil-and-vinegar dressing, or, to a lesser extent, mayonnaise, you’re also eating a very different type of diet from someone who isn’t.

In this case we have a plausible mechanism, and a suggestion of temporality – correcting a historical deficiency of omega-3 fats in a population with very low intake of them would be expected to improve the blood clotting aspect of fatal heart attacks. Other foods could have supplied the ALA, but soy oil happened to be the source available. The association was only significant when the oil was used in salads, and stronger in women taking vitamin E supplements, but in these cases it satisfied the Bradford Hill criteria for strength, and is broadly consistent with the RCT analysis of Ramsden et al.[6]
This example seems to satisfy all Bradford Hill criteria to some extent, if considered as an correction of a deficiency analogous to the correction of a vitamin deficiency, but much less so if considered as the effect of a substitution for saturated fat (especially considering the body of evidence that a substitution for carbohydrate would be at least as beneficial).

On balance we’d say there isn’t a case as far as Bradford-Hill’s criteria are concerned to say anything about spreads and benefit.

Vegetable oils and spreads – some evidence for harm?

So – is there any evidence that non-dairy spreads and cooking oils have harmful effects? You’ll find plenty of mechanistic arguments and non-human experimental evidence that they do in the literature. But remember Bradford Hill’s criteria – an epidemiological association is convincing when it’s attached to mechanisms, but is also strong (RR approaching 2 or greater is best, though 1.5 is usually accepted), consistent (not contradicted by directly comparable studies), and has a dose-response (more seems worse).

Criteria 3, 5, and 7: specificity, biological gradient, and coherence

Age-related macular degeneration is a common cause of visual impairment and blindness in older people.

A case-control study gave the following results.[7]

Higher vegetable fat consumption was associated with an elevated risk for AMD. After adjusting for age, sex, education, cigarette smoking, and other risk factors, the odds ratio (OR) was 2.22 (95% confidence interval [CI], 1.32-3.74) for persons in the highest vs those in the lowest quintiles of intake (P for trend,.007). The risk for AMD was also significantly elevated for the highest vs lowest quintiles of intake of monounsaturated (OR, 1.71) and polyunsaturated (OR, 1.86) fats (Ps for trend,.03 and.03, respectively). Higher consumption of linoleic acid was also associated with a higher risk for AMD (P for trend,.02). Higher intake of omega-3 fatty acids was associated with a lower risk for AMD among individuals consuming diets low in linoleic acid, an omega-6 fatty acid (P for trend,.05; P for continuous variable,.03). Similarly, higher frequency of fish intake tended to reduce risk for AMD when the diet was low in linoleic acid (P for trend,.05). Conversely, neither omega-3 fatty acids nor fish intake were related to risk for AMD among people with high levels of linoleic acid intake.

This was followed by a prospective study by the same authors looking at AMD progression (important because temporality, the presumed cause preceding the effect, which cannot always be shown in case-control studies, is another of the Bradford-Hill criteria), which confirmed the associations above, but also found that nut consumption was protective.[8] This is interesting, because nuts are a good source of linoleic acid, indicating that linoleic acid in whole foods (where some of it is in phospholipid form) may behave differently from linoleic acid in vegetable oils, where the phospholipids have been removed by refining.

The prospective study found that all fats were associated with AMD – however, there was no dose response in the case of saturated fats. Dose response is an important part of the Bradford Hill criteria – if something is truly  harmful, more should (usually) do more harm than a little.

One study, NHANES II, did not find a significant correlation between dietary fats and AMD, however this study failed to separate vegetable oils from other sources of fat, and did not provide a sufficiently detailed breakdown of its results.[9]

This is an example that fulfills many of the Bradford Hill criteria. Indeed it already appears in textbooks as an example of the role of peroxidation in oxidative stress diseases. It has specificity because the retina of the eye is exposed to concentrated UV radiation, and plausibility because linoleic acid and ALA are uniquely prone to peroxidation in vivo. It is known not to be the only factor in AMD, yet shows a strong association, increasing our confidence that it is a factor increasing risk.

One of the predicted harms of higher vegetable oil intake is increased cancer risk, due to the peroxidisabilty of polyunsaturated fats, as well as their use by some types of cancer cells. However, this correlation is not usually a strong or consistent one, because exposure to carcinogens and diet both vary by occupation and socioeconomic class, and because cancer, unlike heart disease, subdivides into many discrete diseases, the risk of which is relatively rare. Further, just agreeing to be in a diet study has a significant effect on reducing future cancer risk. However, there are some exceptions.
The use of vegetable oils for high temperature cooking is fairly consistently associated with lung cancer risk in women using them, for example in this case-control study of women in Gansu, China using rapeseed oil (as far as we can tell, this is the name for canola oil in modern China; at any rate, it comes from the same species and is thought to be healthy) for wok cooking.[10]

A useful feature of this study was that rates of two important confounders, deep fryer cooking and smoking, were very low.

The odds ratio (OR) for lung cancer associated with ever-use of rapeseed oil, alone or in combination with linseed oil, was 1.67 (95% CI 1.0-2.5), compared to use of linseed oil alone. ORs for stir-frying with either linseed or rapeseed oil 15-29, 30 and > or =31 times per month were 1.96, 1.73, and 2.24, respectively (trend, P=0.03), relative to a lower frequency of stir-frying. Lung cancer risks also increased with total number of years cooking (trend, P<0.09). Women exposed to cooking fumes from rapeseed oil appeared to be at increased risk of lung cancer, and there was some evidence that fumes from linseed oil may have also contributed to the risk.

In a Hong Kong case-control study in which deep frying was a common style of cooking, the risk was even higher – indeed, similar to that of smoking.[11] Peanut, corn, and canola were the main oils used (there was little difference between them in this study).

The ORs of lung cancer across increasing levels of cooking dish-years were 1, 1.17, 1.92, 2.26, and 6.15. After adjusting for age and other potential confounding factors, the increasing trend of ORs with increasing exposure categories became clearer, being 1, 1.31, 4.12, 4.68, and 34. The OR of lung cancer was highest for deep-frying (2.56 per 10 dish-years) followed by that of frying (1.47), and stir-frying had the lowest OR (1.12) among the three methods.

The first study is curious because linseed oil, an oil very high in ALA, and one which no-one in the West would use for cooking, seemed safer than rapeseed oil. In the recent Harvard study on dietary fat and mortality, based on Nurse’s Health Study data, ALA was associated with cancer mortality (HR 1.12; 95% CI, 1.04, 1.20). There was both a dose-response and a temporal response (the association was only seen with longer exposure). [12]This association is weak, but lung cancer is only one type of cancer, canola oil only one source of ALA, and ALA rich foods can be used in various ways. The Harvard research analyses foods, rather than the ingredients they are made with, so there’s no information on how much canola oil was being used, but in NZ it seems to be the most common cooking oil. However, the idea that cooking oil fumes cause lung cancer seems to be accepted; yet, here in New Zealand, we’re told to use canola oil in place of animal fats or coconut oil (saturated fat wasn’t associated with cancer mortality in the Harvard study).

This is a case that not only fulfills Bradford Hill criteria for causality (the product of heating the ALA in these oils protects lung cancer cells against apoptosis in vitro), but also fulfills his example of a practical intervention. We could look for less probably carcinogenic oils and fats and introduce (or re-introduce) them into the limited environments of kitchens without too much injustice if we are wrong, provided they are no more harmful once eaten.

Since the removal of PHO trans fats from the food supply, the use of palm oil, the vegetable oil highest in the main saturated fats palmitic and stearic acid, has increased in NZ. Palm oil consumption is equal to that of butter, and most of it goes into non-dairy spreads and other processed foods. The “Myth Buster” section of the Listener article we responded to in the last post failed to mention palm oil use in spreads. Palm oil contains a greater amount of the supposedly “bad” saturated fat palmitic acid than butter, thus defeating the point of using margarine. (However, as the amount of palmitic acid in the blood is controlled by the amount of carbohydrate we eat, and we usually eat much more carbohydrate than palmitic acid, it makes more sense to reduce carbohydrate first, and avoid palm oil, before looking at butter. Coconut oil is very low in palmitic acid). Palm oil production has become a far greater environmental disaster internationally than dairying is said by its worst critics to be for New Zealand. To make matters worse, the European Food Safety Agency recently issued a warning that palm oil contains higher levels of the carcinogen glycidyl, caused by refining at temperatures above 200 degrees C, than those found in other processed oils.[13] New Zealand is still awaiting legislation for the mandatory labelling of palm oil, which often appears on food labels as “vegetable oil”. Remember, the New Zealand population has only been exposed to trans fat, palm oil, and interesterified fat products because locally produced animal fats like butter have been supposed, on inadequate evidence, to be harmful, and because a massive international industry exists to profit by supplying us with artificial substitutes.

So there could be a future increased health risk, as well as the ongoing environmental disaster, caused by our rush to consume palm oil, all in the name of avoiding butter and animal fats. However, there’s no epidemiological study looking at the impact of palm oil in Western countries (nor any for interesterified fats). Bradford Hill can’t help us when studies don’t ask the right questions. Most of the studies we’ve looked at weren’t designed to tell us whether getting our polyunsaturated fats from refined oils instead of real foods was a good idea or a bad one, though we can be pretty sure that they’re not as healthful as they were once heated above 200 degrees C, whether in cooking or refining.


We love the way that Bradford Hill’s thinking does more than just help us decide whether to say yes or no to the question of “does X cause (or prevent) Y?”- it can also lead us into a deeper understanding of what the evidence really means.

The case for benefit from PUFA oils and spreads isn’t met, except for the case for correcting a deficiency of LA or ALA –  directly analogous to correcting a vitamin deficiency (analogy). Regarded in this way only, the case for benefit should be clear, but can only apply to oils and spreads in cases where oils are the only source of these fats – this doesn’t have to be the case for ALA, and of course it is not the case for LA in normal diets.
Anyone eating a higher fat, real food diet is likely to have an optimal intake of LA and at least a sufficient intake of ALA or other omega-3 fats without relying on these supplementary sources.

 For harm from oils and spreads, there is no strong general case for harm, but there is a case when some oxidising stressor is introduced. This includes UV light (in the eye) for AMD, and heat (in the pan) for lung cancer. PUFA manifests this harm in free oil form (there is an analogy here with experimental alcoholic liver disease, where high-PUFA oils in the diet are convincingly harmful, but PUFA in phospholipids can be protective, as are saturated fats, in a context of oxidative stress; we haven’t covered this evidence because its epidemiological component is so far minor).
And then there are the harms untested – novel foods should be monitored better than they are. Absence of evidence isn’t evidence of absence. The effect of heat on palm oil fats, and to a lesser extent other oils, during refining predicts harm for human health, but epidemiological evidence that confirms (or refutes) this may take decades to appear.

A low-butter spread you can make at home.

Supposing you like the taste of butter, want to avoid potentially harmful refined oils, but are also interested in reducing the amount of saturated fat you eat. Or maybe you want to do your bit to reduce the environmental impact of dairy farming. We suggest adapting a recipe for “Sunbutter” from Gayelord Hausers'”Treasury of Secrets” (1963 edition).

Gayelord Hauser was a diet adviser to the stars in the golden age of Hollywood, who advocated (among other things) low carb diets for weight loss, and the use of what later became known as “health food supplements” such as brewer’s yeast, molasses, and wheat germ oil. His books contain a simple recipe for a low-saturated fat spread, using a pound of butter and a cup of sunflower oil. In our new updated version, you’d heat and blend together equal parts butter and extra virgin olive oil. The result is spreadable straight out of the fridge, and tasty. This might just be the main benefit of the recipe. NZ refrigerators used to have a butter conditioner – a warm section of the fridge, just the right temperature to keep your butter spreadable. These went out with the anti-butter, saturated fat will kill you campaigning of the Heart Foundation and Rod Jackson in the 1990s. Such a loss…

Unlike the original Sunbutter, this mixture will have almost exactly the same fatty acid composition as your own fat stores (credit to Steve Phinney for this insight), and that’s exactly the kind of healthy fat you want to be running on.
And you don’t need to use anything to make it that you wouldn’t normally want in your food.


[1] Praagman J, de Jonge EA, Kiefte-de Jong JC, Beulens JW, Sluijs I, Schoufour JD, et al. Dietary Saturated Fatty Acids and Coronary Heart Disease Risk in a Dutch Middle-Aged and Elderly Population. Arterioscler Thromb Vasc Biol. 2016; 36(9): 2011-8.

[2] Praagman J, Beulens JW, Alssema M, et al. The association between dietary saturated fatty acids and ischemic heart disease depends on the type and source of fatty acid in the European Prospective Investigation into Cancer and Nutrition-Netherlands cohort. Am J Clin Nutr2016;103:356-65.

[3] Margarine intake and subsequent coronary heart disease in men. Gillman MW, Cupples LA, Gagnon D, Millen BE, Ellison RC, Castelli WP. Epidemiology. 1997 Mar;8(2):144-9.

[4] Liu Q, Rossouw JE, Roberts MB, Liu S, Johnson KC, Shikany JM, Manson JE, Tinker LF, Eaton CB. Theoretical Effects of Substituting Butter with Margarine on Risk of Cardiovascular Disease. Epidemiology. 2017 Jan;28(1):145-156.

[5] Hu FB, Stampfer MJ, Manson JE, et al. Dietary intake of α-linolenic acid and risk of fatal ischemic heart disease among women. Am J Clin Nutr. 1999; 69(5): 890-897.

[6] Ramsden CE, Zamora D, Leelarthaepin B, Majchrzak-Hong SF, Faurot KR, Suchindran CM et al. Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis

[7] Seddon JM, Rosner B, Sperduto RD, et al. Dietary fat and risk for advanced age-related macular degeneration. Arch Ophthalmol 2001;119:1191–9.

[8] Seddon JM, Cote J, Rosner B. Progression of age-related macular degeneration: association with dietary fat, transunsaturated fat, nuts, and fish intake. Arch Ophthalmol 2003;121:1728–37.
[9] Heuberger RA, Mares-Perlman JA, Klein R, et al. Relationship of dietary fat to age-related maculopathy in the Third National Health and Nutrition Examination Survey. Arch Ophthalmol 2001;119:1833–8.

[10] Metayer C, Wang Z, Kleinerman RA, et al. Cooking oil fumes and risk of lung cancer in women in rural Gansu, China. Lung Cancer. 2002 Feb;35(2):111-7.

[11] Yu IT, Chiu YL, Au JS, Wong TW, Tang JL. Dose-response relationship between cooking fumes exposures and lung cancer among Chinese nonsmoking women. Cancer Res. 2006 May 1;66(9):4961-7.

[12] Wang DD, Li Y, Chuive SE, et al. Association of specific dietary fats with total and cause specific mortality. JAMA Intern Med. Published online July 5, 2016.

[13] Panel on Contaminants in the Food Chain. Risks for human health related to the presence of 3- and 2-monochloropropanediol (MCPD), and their fatty acid esters, and glycidyl fatty acid esters in food. EFSA Journal 2016;14(5):4426 [159 pp.].