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.

red-meat

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?

Potter

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…..you’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.

References

[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. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808795/

[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.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2803089/

[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.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3985213/

[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 https://doi.org/10.1371/journal.pone.0088278

[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.
http://ajcn.nutrition.org/content/89/5/1620S.full

[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.

 

11 comments

  1. Ian Partington · · Reply

    Is epidemiology even a true science? Or a bunch of prejudicial academics seeing what they want to see?

    1. Epidemiologists used to be more humble – then it’s very much a real science – but when you think you’re saving the planet, I suppose you feel like Superman.

  2. Eat everything in moderation – smaller portions and go run around the block afterward. It’s not rocket science.

    Ha, just kidding.

    Thanks for this one. The red and processed meat thing is something I’ve never looked into properly, probably because I don’t think I’d stop eating it, even if it was truly bad news.

    Not sure what the lamb is like in shops over the ditch, but in Oz, they’re very fatty, which I assume equates to being finished on grain. I used to think most sheep were pasture fed, but it seems that is increasingly not the case. I dunno, it’s hard to tell.

    http://agriculture.vic.gov.au/agriculture/livestock/sheep/feeding-and-nutrition/feedlotting-lambs

    1. I think sheep are naturally fatty, at least the ones raised in NZ. I suppose you could use grain to fatten lamb if you wanted to slaughter them early or the season was poor; in your link this looks like it’s being done for “prime” lamb, i.e. more expensive meat, mostly exported or eaten in expensive restaurants. More fool them. Note fattening with grains causes “lamb deaths” as a side effect, much as in humans.

  3. Here’s a thought – this was a population of mostly retired people, 50+ at baseline.
    What if those with higher BMI and higher red meat intake were given more medication, and the excess of liver and respiratory disease mortality is a side effect of over-prescription, and lipid lowering in an elderly population where it may do more harm than good?
    The latter is hard to be sure of because of indication bias (if you’re prescribed a statin because of high LDL you were at lower risk of respiratory mortality to begin with, so they tend to look good for COPD), but the former is certainly plausible.

  4. “Sheep are naturally fatty”. I imagine that might be hard to fathom for a certain group of people who argue, with a straight face, that gorillas are so buff because they eat plants.

    Perhaps sheep are raiding the chook shed at night. Or hunting and devouring foxes and rabbits.

    Yes, that makes perfect sense.

  5. Here’s an study that makes the point that some calculations about efficiency of farming methods are premature.

    “Thus, considering both quantity and quality, the value of the proteins in the animal products for human consumption (in this case in milk and beef) is 2.15 times higher than that of proteins in the potentially human-edible plant protein inputs. The results of this study emphasize the necessity of including protein quality changes resulting from the transformation of plant proteins to animal proteins when evaluating the net contribution of livestock to the human food supply. Furthermore, these differences in protein quality might also need to be considered when choosing a functional unit for the assessment of environmental impacts of the production of different proteins”

    https://www.ncbi.nlm.nih.gov/pubmed/27160573

    This is from 2016 – the “functional unit” for this sort of maths still won’t have been chosen yet.
    And this is ignoring the fat energy, including both essential and beneficial fatty acids, produced or concentrated from low-fat feeds. And the fact that, with regard to pasture, the protein and energy in grass is 100% unavailable to humans anyway.

    The environmental economics of farming is obviously of critical importance, but it seems to be at about the stage, with regard to its mathematics, that nutritional science had reached when Atwater started his experiments.
    We’ve seen the unintended consequences of rushing into dietary changes based on undeveloped (yet not allowed to be contested) science before. Why not start with the things everyone agrees on – pasture is better than feedlot, palm oil is a scandal?

  6. Excellent review!
    The tolerated and well-maintained confusion between grass fed and grain fed crop agriculture is a “grand Classique ” of environmental advocates.

  7. chris c · · Reply

    Well this certainly explains why we became extinct millennia ago. Oh, wait . . .

    I didn’t see ONE mention of carbs. I strongly suspect there is a world of difference between eating grass-fed meat with vegetables and grain-fed meat with the bun, fries and Big Gulp which the “study” carefully ignored.

    Looks like yet another study where they throw a lot of numbers into a grinder then extract the ones that “prove” what they have already decided. Hardly worth the paper it was wiped on.

    I was just walking on a marsh which is flooded in winter for the geese and ducks etc. and which builds up the soil fertility, after which they let the water out and graze beautiful tasty beef cows. Elsewhere we have hills and mountains where you can graze sheep, and shoot grouse, no way could you grow Holy Health Grains,

    Incidentally I know someone who is researching small mammal populations – so far they are highest in sheep meadows. How many voles have to die before the vegans are happy?

    1. This doesn’t surprise me. There are sheep being grazed around where I live, and these pastures are also used by a few bird species who even seem to nest in the wilder corners.
      Pastures are much closer to the ancestral environment of ruminants than are feedlots, and animals living in their ancestral environments never harmed the planetary health before, despite existing in truly massive numbers. It’s amazing to me that people can exhaust the fossil deposits of millions of years and deplete the ancient forests in a few centuries by burning them, almost completely trashing the planet, then, belatedly looking around for some way of making themselves useful, put the blame on the animals without differentiating between those we’ve started raising in a wasteful manner and those, a high enough proportion of the total still, who are just doing what they’ve always been doing.
      The disconnect between the environmental effect of dairy, meat, fishing, and plant monoculture on the one hand, and advice to eat vegetarian/flexitarian diets (more dairy and fish needed for this be healthy), lean meat, low fat dairy, avoid animal fat (which is being produced whether people eat it or not), and use extra oils including even palm oil on the other hand has to be the most striking example of cognitive dissonance – environmental arguments are being selectively cited when they seem to support the dietary guidelines and a wasteful “value-added” food industry and completely ignored when they appear to contradict them.

  8. chris c · · Reply

    Wheat fields are among the most barren and chemically battered environments, not to mention all the diesel used in the cultivation and harvest. Rape fields aren’t much better. Yet farmers are paid subsidies to grow this stuff – they only get to hold the money for a while though before passing it on to the manufactured foodlike substance industry through lower prices, and even so some years they are paid less than the cost of production.

    Add in the costs of the antidotes – like statins, BP and diabetes meds etc. and it is a hugely profitable clusterf*ck. In which the veg(etari)ans are fighting alongside ILSI etc.

    Human health has been wrecked in a generation, us folks who can actually remember a time before low fat diets can also remember a time before “epidemics” of obesity and metabolic disease. We are told these occur because people are not actually following dietary recommendations, so the corollary is that we were secretly eating low fat diets for millennia before they were invented, and as soon as they were invented we stopped. How likely is that?.Do they seriously believe themselves? ok rant over

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