Hi,
there are some very disputed assertions in this short opinion which has been apparently peer-reviewed.
It is simple but for scientists, it is fundamental to point that the authors began their piece with a big mistake. Bacon is not red meat. So they perfectly exemplified the huge risk of error of questionnaires in observational studies. Reason why those studies are imprecise, weak and without any evidence of causality whatever the sens of it. The reason why randomization will balance this kind of mistakes and control will suppress them.
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 specific food." No. It is nonsense to make a rule for drugs and another for diets. Simply this is at heart of the problem. The high profile authors, evoked in this opinion, made their career by making such a double standard an obvious knowledge and in the same time selling their observational studies with a low association between factors as fuzzy as grains, fat or meat... It is a shame that observational studies on diet of 10 years or more were published with only one assessment by questionnaire at the beginning of the "prospective" study. Aside from the fact that 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 a study which shows that junk food is efficient in gaining weight on a short time basis (https://www.ncbi.nlm.nih.gov/pubmed/31105044). So patients and physicians worth high-quality studies. I mean RCT in order to solve the obesity epidemics that high profile nutritionists failed to curb. It is also very untrue to reassess: "Given that RCTs with foods or food groups are not possible". The authors concentrated their criticism against RCT only because they took the side of observational studies. They chose the weakest evidence, aka association of factors because they don't want to embark in causality studies.
Furthermore the authors made two assertions in the same sentence which are not relevant about red meat. "The authors also chose to leave out all artificial 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. The major food sources of acrylamide are French fries and potato chips; but also crackers, bread, and cookies; breakfast cereals those last foods that high profile nutritionists advise eating if they are made of whole flour. The 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 those 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 life. Another bad study is to give meat to a non-carnivore as it is a poor mechanistic study to give a high-fat diet to rabbits. 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 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769029/)! Interestingly one of the study reviewed in this paper (https://www.sciencedirect.com/science/article/pii/S0027510702001641?via%3Dihub) didn't find an association between well done or very well done meat (processed or not) 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 assessable and measurable risk. it is rather surprising that they didn't mention the true carcinogens in high temperature cooked red or processed meat: heterocyclic amines and polycyclic aromatic hydrocarbons. These organic compounds which are also produced by high-temperature cooking of white meat, fishes and vegetable protein although in less quantity.
Then they came to the demonstration that Canadian authors cherry-picked studies. Doing that they also destroyed observational studies as the meta-analysis of RCT is far less subjected to contest; If red meat is the hypothesis you cannot eliminate an RCT which stated that. Then they discussed the 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. Eventually, they backed the 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. We mentioned previously the RCT on processed food that they quoted and it is a pity that they didn't recognize in quoting it that such a paper, so rare that it is, is more powerful than dozens of observational studies. the following statements are interesting because they are only authors opinion. We were waiting for a better backing than wishful thinking and political correctness.
Two very obvious errors, however, were made at the end.
First, they compare the review about meat with an, according to them, complacent subsidised review about sugar from the same lead author. The Canadian meat meta-analysis would be corrupted by a precedent study on sugar because of hidden conflict of interests? 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 finding the truth.
Secondly, 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 a vegan diet.
Then they came to the demonstration that Canadian authors cherry-picked studies. Doing that they also destroyed observational studies as the meta-analysis of RCT is far less subjected to contest; If red meat is the hypothesis you cannot eliminate an RCT which stated that. Then they discussed the 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. Eventually, they backed the 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. We mentioned previously the RCT on processed food that they quoted and it is a pity that they didn't recognize in quoting it that such a paper, so rare that it is, is more powerful than dozens of observational studies. the following statements are interesting because they are only authors opinion. We were waiting for a better backing than wishful thinking and political correctness.
Two very obvious errors, however, were made at the end.
First, they compare the review about meat with an, according to them, complacent subsidised review about sugar from the same lead author. The Canadian meat meta-analysis would be corrupted by a precedent study on sugar because of hidden conflict of interests? 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 finding the truth.
Secondly, it is hard to believe that the authors decided to conclude their opinion piece by a so predictable greenwashing. The EAT-Lancet initiative 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 a vegan diet. This kind of reasoning is reductionist as it leads to blaming 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 sufficient animal products and suffer several deficiencies. 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. Another time 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, effluent waste, and water and land consumption. The issue is destructive farming — not whether you eat meat 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 which is managed very differently in the different countries and according to ancestral or new practices. In a recent paper (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5799208/), C. Christie et al brought the evidence that excess calories whatever it comes from do have a bigger impact. Among those excess calories, processed foods have a bigger impact in general because they need more energy to be produced, packaged, transported and finally more frequently treated as waste. Excess calories are consumed in developed countries (http://www.fao.org/faostat/en/#data/FBS/visualize), 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, carbohydrate, and minerals. On the contrary sugar and fats in processed foods, which are in excess, are very dense foods with minimal water.
Finally, we have to recall the nutritional advantages of meat for humans a life long.
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 decreases 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 in moderation, meat and offal have an important role in maintaining good health through its supply of high-quality nutrients. In the setting of a flexitarian diet like in the blue zone countries, the benefits of meat add those of fishes and seafood, more high fibre, plant-based foods, with the nutritional durability of an omnivorous diet.
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 decreases 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 in moderation, meat and offal have an important role in maintaining good health through its supply of high-quality nutrients. In the setting of a flexitarian diet like in the blue zone countries, the benefits of meat add those of fishes and seafood, more high fibre, plant-based foods, with the nutritional durability of an omnivorous diet.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6559336/
https://www.ncbi.nlm.nih.gov/pubmed/23497300/
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0191767
"This is a good example of what I call nutritional nihilism, an approach that insists that because observational studies are based on self-reported information and necessarily flawed, their conclusions are unscientific and should be discounted. Therefore, because we can’t do more rigorous studies, we should not advise the public about diets best for health or the environment."
"The conclusions fall into the category of “everything you thought you knew about nutrition is wrong.” This rarely happens. Science usually works incrementally, not in one enormous reversal like this."
Are we collectively biased by this idea that conventional medicine is wrong and that at one point we shall see the disruption?
https://jamanetwork.com/journals/jama/article-abstract/2712745
https://www.nytimes.com/2019/09/30/health/red-meat-heart-cancer.html
https://www.youtube.com/watch?v=__FEUvehZA4
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