Red meat, ancestral diet and environment are not to be solved with prohibitions. I describe in this opinion the biases of observational studies and the mistakes in environment issues.

1. 16/10/2019 Red meat bashing and human ancestral diet
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Red meat bashing and human
ancestral diet
By Guy-André Pelouze - 16.10.2019
Con ict of interest: The author received no fee nor grant for this commentary. He is
personally omnivorous and practices thoracic and cardiovascular surgery.
THERE IS, OBVIOUSLY, SINCE THE END OF WWII, A BATTLE IN THE FIELD OF HUMAN NUTRITION:
ANIMAL PRODUCTS ARE VILIFIED BY SOME ACADEMICS ON THE GROUNDS OF STUDIES WHICH MERELY
ARE OBSERVATIONAL.
The same academics took power and heavily in uenced the nutritional guidelines. This is
why of cial recommendations regarding of human health and political decisions stir up some
very disputed assertions. This short opinion published in the BMJ[1] sums up them very
interestingly. Tim Spector and Christopher Gardner (subsequently named the “authors”)
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discussed the recent recommendations issued by Canadian researchers from Mac Master
University[2] that there is no evidence to cut on red meat because of health risks. They warn
against the work of these Canadian researchers who recently demonstrated that one might
be skeptical on scienti c evidence of the red meat bashing. It is not surprising that such a
skeptical attitude is unbearable for those who believe that the weak and inconstant
associations between meat consumption and chronic diseases –even death – are non-
questionable. It does not matter to them that in those studies the type of meat was very
imprecise, as the type of transformation, that those associations were mainly found in
quartiles of high consumption and predominate in groups of people with risky lifestyle (male
sex, smoking, alcohol). More generally this debate, whatever its polarization, is not only a
methodological one or a civilization issue; it is simply a question of ef ciency in the actual
battle against diabesity. As a physician, this is the aim of our commitment to patients
because diabesity is a public health priority. The worldwide prevalence of overweight and
obesity has approximately doubled since 1980. Nearly a third of the world’s population is
now overweight or obese. Obesity rates have increased in all ages and both sexes
irrespective of geographical locality, ethnicity or socioeconomic status. This trend is similar
across regions and countries, although absolute prevalence rates of overweight and obesity
varied widely. In this battle, this is not an opinion, academic authors and governments failed
to tackle the problem by promoting their well-known food pyramids[3]. On the other hand,
red meat consumption is not at the origin of this number one problem in public health.
IT IS SIMPLE BUT, FOR SCIENTISTS, IT IS FUNDAMENTAL TO POINT OUT THAT THE AUTHORS BEGAN
THEIR PIECE WITH SIGNIFICANT CONFUSION.
Bacon is not red meat. In mixing them authors perfectly exempli ed the huge risk of error in
observational studies. The reason why those studies are imprecise, weak and without any
evidence of causality whatsoever. On the contrary, randomization will balance this kind of
mistakes and control of diet will suppress them. In mixing bacon, red meat, processed meats
and environmental issues authors deliberately began to add incomprehensiveness to an
already complex issue. As it is their mantra they continued in this path. “The criteria are well
suited to studies of pharmaceuticals when there are randomized, double-blind, placebo-
controlled trials available, but not for studies of meat, eggs, vegetables or any speci c food.”
No. It is nonsense to make a rule for drugs and another for diets. Simply this is the heart of
the problem. The high-pro le authors, evoked in this opinion piece, made their career by
making such a double standard an obvious knowledge and at the same time selling their
observational studies with a low association between factors as fuzzy as the Mediterranean
diet, grains, fat, dairy or meat… It is a shame that observational studies on diet of 10 years or
more were published with only one or two assessments by self-reported questionnaires at
the beginning of the “prospective” study. Aside from the fact that other academic authors
and organisations disagree with this impossibility to do RCT in diets, several very high-
quality papers were published and recently. Kevin D. Hall did such RCT which shows that
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junk food causes weight gain on a short time basis[4]. So, patients and physicians are worth
high-quality studies. There are several innovative paths to get rid of observational studies.
The rst is the RCT. For instance, RCT brings quality information in order to help to solve the
obesity epidemics that high pro le nutritionists failed to curb. It is untrue to assert: “Given
that RCTs with foods or food groups are not possible”. By designing RCT it is possible to
precisely assess each type of food or food group in the setting of a clear hypothesis. The
second is the use of genetic variants as instruments to test the causal associations[5]. The
third is personalised nutrition which is the way to discriminate the effects of nutriments or
carcinogens on different genomes and epigenomes[6].
Authors chose the weakest evidence, aka association of factors because they are reluctant
to embark on causality studies.
FURTHERMORE THE AUTHORS MADE TWO ASSERTIONS IN THE SAME SENTENCE WHICH ARE NOT
RELEVANT TO RED MEAT.
“The authors also chose to leave out all arti cial ex-vivo lab studies and animal studies,
included in other meta-analyses, that have, for example, implicated nitrites or acrylamides as
carcinogens. “ The carcinogens quoted are totally out of the subject. Is it necessary to point
out that nitrites and acrylamide are not present in red meat? How this could be possible in a
peer-reviewed opinion? Technically, processed meat means pork, beef or duck that has been
salted and cured, with or without smoking. A fresh pound of red meat is not processed. A
hard stick of cured salami is. The health risk of bacon, if any, is largely to do with two food
additives: potassium nitrate (also known as saltpetre) and sodium nitrite. On the other hand,
major food sources of acrylamide are French fries and potato chips; but also, crackers, bread,
and cookies; breakfast cereals those last foods that high-pro le nutritionists advise eating if
they are made of “whole our”. Furthermore, animal studies and other “mechanistic studies”
are not relevant to the new strict analysis of the observational studies about red meat by
Canadian authors. Indeed, animal and mechanistic studies are only warning studies for
launching clinical trials. No more no less. And another time the great carnivores do not
exhibit cancers or CVD after eating meat all their lives. An example of aw animal study is to
give meat to a non-carnivore as it is a poor mechanistic study to give a high-fat diet to
rabbits to explain atheroma. Last but not least they didn’t mention the 2010 review which
showed that eating charred, smoked, well done red meat is associated with a higher risk of
colorectal cancer only in smokers[7]! Interestingly one of the studies reviewed in this
paper[8] didn’t nd any association between well done or very well-done meat (processed
or not) and health issues below 5 steaks/week. We are very near to the advice of the
Canadian authors who concluded that until 3 steaks per week there is no measurable risk. In
order to understand the complexity of the issue of cancer and meat consumption we need to
be clear about the potential causes. It is rather surprising that they didn’t mention the proven
carcinogens in high temperature cooked red or processed meat: heterocyclic amines and
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polycyclic aromatic hydrocarbons. These organic compounds which are also produced by
high-temperature cooking of white meat, sh and vegetable protein although in less
quantity are not present in fresh meat nor in low temperature cooked meat.
THEN THEY CAME TO THE DEMONSTRATION THAT CANADIAN AUTHORS CHERRY-PICKED STUDIES IN
THEIR META-ANALYSIS.
Authors argued that Canadian researchers eliminated some observational studies in order to
bias the nal results. They point out the eviction of Lyon heart study and PREDIMED but
they don’t prove that taking into account these studies would have changed the conclusions
of the revision meta-analysis about red meat. Doing that, they again delegitimated
observational studies. Indeed, meta-analysis of RCT are far less subjected to contest; if red
meat consumption is the hypothesis to test, you cannot eliminate an RCT which stated that.
In observational studies, the selection is a very complex process as their design and the
modelling of multivariate analysis in uence the results. Eventually, they agreed with
Canadian authors: “Previous summaries, which have been more inclusive, have shown
modest health risks for red meat, but clear links between processed meat, heart disease and
early death. The evidence for cancer causation is less clear-cut, and several trials of meat
reduction have not resulted in lowering of cancer risks. “ In the same paragraph, they also
recognize that the issue is not red meat but junk food, a point we strongly agree with.
Nonetheless, RCT are very rare despite being more powerful than dozens of observational
studies.
THEN COME THE FOLLOWING STATEMENTS WHICH ARE ONLY AUTHORS’ OPINION.
They wrote: “but in our view, we should all be eating less meat and more high bre, nutrient-
dense foods that include many vegetables, legumes, fruits and nuts and seeds.” We were
waiting for a better backing than wishful thinking and political correctness. This advice is no
more than a copy/paste of the average, standardized, non-personalised nutritional guidelines
which proved to be meaningless and inef cient. Nonsense.
BACK TO THE OPINION PIECE I WANT TO POINT OUT TWO ERRORS THAT WERE MADE AT THE END.
FIRST, WHY REIGNITE A CONTROVERSY IN A BIASED MANNER?
They compare the review articles about meat with an, according to them, a complacent
subsidised paper about sugar from the same lead author. Making it short, the Canadian meat
meta-analysis would be corrupted by a precedent study on sugar because of hidden con ict
of interests. It is a concern. But one may wonder why the EAT-Lancet initiative that they also
quoted is not under the same scrutiny? It is suspicious to imply that government subsidies,
non-pro t organisation subsidies or any other subsidy are neutral… In order to get out of this
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5. 16/10/2019 Red meat bashing and human ancestral diet
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biased debate, I think we don’t need such a suspicion. It is only a matter of good sense or
bayesian evidence: we eat sugar approximately since 1800 and meat since at least 500 000
years. That could help in nding the truth.
SECOND, IT IS HARD TO BELIEVE THAT THE AUTHORS DECIDED TO CONCLUDE THEIR OPINION PIECE BY A SO
PREDICTABLE GREENWASHING.
The EAT-Lancet initiative that they quoted, is not a new study. It is not a meta-analysis. It is
indeed a very sophisticated but biased piece of statistical manipulation in order to impose
not less meat but a vegan diet. Their opinion is respectable as long as they state it sincerely.
I think that this kind of reasoning is reductionistic as it leads to blaming all people around the
planet for eating too much meat. While for instance, south European people eat a very
moderate amount of meat and numerous other populations don’t eat suf cient animal
products and suffer several de ciencies. It is the same reasoning which is used by bad
teachers who punish all the classroom instead of targeting those who are making the
heckling. Again, this assertion is not backed by evidence. All agricultural practices have been
found to have a variety of effects on the environment. Some of the environmental effects
that have been associated with meat production are pollution through fossil fuel usage,
animal methane, ef uent waste, and water and land consumption. The issue is destructive
farming, not whether you eat meat or dairy or vegetables or grains. Another issue is the
quantum of those impacts. Contrary to different assertions in the different EAT-Lancet
papers, the matter of anthropogenic emissions is extremely complex and still poorly known
in details. Particularly meat production is a multifactorial process which is managed very
differently in different countries and according to ancestral or industrial practices. The
amount of direct GHG emissions of animal husbandry is 2,3 GigaTons of CO2 equivalent id
est 5% and indirect GHG emissions linked to all meat, eggs and dairy products are 4,8
gigatons of CO2 equivalent per year or 9.5% of all anthropogenic emissions. It is important
to address these emissions with rationality that is why indirect emissions are the true target,
not animals. Indirect emissions are the most important and are largely improvable through
energy transition and other agricultural practices, the same means used in other sectors of
agriculture. Direct emissions are less avoidable but represent only half of the indirect GHG
emissions.
As a matter of fact, in the United States 60% of calories come from re ned sugar, re ned
grains and re ned omega-6 seed oils, which is saying that meat consumption does not have
a prominent role in obesity and type 2 diabetes. It is remarkable that carbs and vegetable
oils are recommended by food pyramids. In a recent paper[9], C. Christie et al brought the
evidence that excess calories, whatever it comes from, do have a big environmental impact.
Among those excess calories, processed foods have a bigger impact in general because they
need more energy to be produced, packaged, transported and nally more frequently treated
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as waste. Excess calories are consumed in developed countries[10], but it is not meat which
brings calories in excess because meat and poultry are composed of naturally occurring
water, muscle, connective tissue, fat, and bone. The muscle is approximately 75% water
(although different cuts may have more or less water) and 20% protein, with the remaining
5% representing a combination of fat, carbohydrates, and minerals. On the contrary, sugar
and fats in processed foods, which are in excess, are packed in very dense foods with
minimal water increasing signi cantly the number of calories per day.
FINALLY, WE HAVE TO RECALL THE NUTRITIONAL ADVANTAGES OF MEAT FOR HUMANS A LIFELONG.
Meat is a very good source of nutritionally complete and digestible proteins, bioavailable
iron, zinc, and selenium and the exclusive source of vitamin B12. Consumption of red meat
has decreased since 2000 in developed countries and the average consumption in Europe is
around three portions a week. This amount of red meat is not associated with any increased
risk in observational studies. When consumed, meat and offal have an important role in
maintaining good health through its supply of high-quality nutrients. In the setting of a
exitarian diet like shown in the blue zone countries, the bene ts of meat add those of sh
and seafood, more high bre, plant-based foods, with the nutritional durability of an
omnivorous diet. Red meat bashing is against human ancestral diet and will increase human
health issues. We should think twice before throwing away red meat production together
with fossil fuels because of environmental issues. There are smarter paths to curb
anthropogenic emissions without endangering human health.
[1] https://blogs.bmj.com/bmj/2019/10/09/bacon-rashers-statistics-and-controversy/?
fbclid=IwAR2453O8TZURygfDz3cz4871bsXTAHhHJ16mhKDHnq7p_3-zjJacTRMmnII
[2] https://annals.org/aim/fullarticle/2752328/unprocessed-red-meat-processed-meat-
consumption-dietary-guideline-recommendations-from
[3] https://www.ncbi.nlm.nih.gov/pubmed/30253139
[4] https://www.ncbi.nlm.nih.gov/pubmed/31105044
[5] https://diabetes.diabetesjournals.org/content/early/2019/06/05/db19-0153
[6] https://www.bmj.com/content/361/bmj.k2173
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769029/
[8] https://www.sciencedirect.com/science/article/pii/S0027510702001641?via%3Dihub
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[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5799208/
[10] http://www.fao.org/faostat/en/#data/FBS/visualize
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meat bashing nutrition observational studies Red meat
GUY-ANDRÉ PELOUZE
Guy-André Pelouze is a renowned surgeon with a keen interest for the progress made in his eld
of work. He pays close attention to changes in doctor’s working conditions and systemic evolutions
that affect the standard of care for patients.
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