Since the 2010s, multiple scientific studies have been published concerning the harmful effects of meat on health. It would increase the risk of cardiovascular disease, Cancerof diabetes or eveninflammation of the intestine. We take stock with Dr Jean-Michel Lecerf, head of the nutrition department of the Institut Pasteur de Lille and author of the book “Meat: a little, a lot, passionately or not at all? “.
Red meat in the dock
The most advanced knowledge concerns the links between meat and cancer. Indeed, in 2015, the International Agency for Research on Cancer (WHO-IARC) ranked the Red meat and processed meat (sausage, cold cuts, etc.) as probably carcinogenic and carcinogenic to humans. The same year, a study by the Anderson Cancer Center (Houston, USA) linked cooked meat to kidney cancer. Cooking would form two substances: PhIP and MeIOx. Filtered by the kidneys, these products would stagnate there, thus increasing the risk of developing cancer. Grilled meat would be the most harmful of all, by generating heterocyclic amines and polycyclic aromatic hydrocarbons, molecules that are also carcinogenic.
For the colorectal cancer, the mechanism differs. Researchers from INRA shed light on the role of heme iron in red meat and charcuterie. Heme iron, composed of an atom of iron and protein, gives this red color to meat. However, during digestion, it is transformed by oxidation into a toxic compound: aldehyde. This promotes mutations at the DNA level and causes cell death in the colon and rectum. With one exception: precancerous cells are very resistant to these attacks. In this way, excessive consumption of red meats and sausages damages the tissue of the colon and rectum, but in addition, selects precancerous cells. “Haem iron is the main hypothesis that explains why red meat is more implicated in cancers”, specifies Dr. Jean-Michel Lecerf. “But genetic factors also come into play.”
Dr. Lecerf recalls that in most studies, an increased risk of cancer is only observed when the consumption of red meat exceeds 100 grams in “counted cooked” quantity, after cooking. He reassures, however, by comparing to cigarettes: “there is only a 17% increase in the risk of cancer with red meat, against 1,000% with cigarette !”
Meat and intestinal microbiota, a delicate balance
The second well-established link is the increased risk of heart disease. Contrary to the widely held idea that blames saturated fats, especially in fatty meats, the problem lies in the modification of certain amino acids under the action of gut microbiota, i.e. all the viruses, bacteria and fungi that populate our digestive tract. These transform carnitine (a molecule present in red meat) into trimethylamine N-oxide (TMAO), a molecule that can modify the metabolism of cholesterol, slow its elimination and promote its accumulation on the arterial walls. “If the diet does not contain enough plant products, we have a bad microbiota which will tend to produce more TMAO”, schematizes the doctor. It should be noted that the increased risk of cardiovascular disease and diabetes is more generally associated with an unbalanced diet, low in plants.
If the Cancer Research Institute recommends not to exceed 500 grams of red meat per week and to limit the amount of cold cuts to 50 grams per day, Dr. Lecerf recommends an even lower meat intake. , in particular for its diabetic patients or those suffering from cardiovascular diseases: “about a quarter of French people consume meat in excess. Often, their entire lifestyle is at risk: physical inactivity and sometimes obesity, diabetes, smoking and alcohol,” he says.
Vegetarianism as a solution?
So why not simply do without meat products? The nutritional qualities of meat do not make it essential. Only the nutrients it contains are essential, which does not prevent them from being found elsewhere. Namely: proteins, iron, zinc and some vitamins – especially group B and in particular B9 and B12. But if you choose to exclude meat, then you have to pay even more attention to the balance of your plate. “In the case of a vegetarian diet of the ovo-lacto-vegetarian type, with dairy products and eggs, this is not a problem”, according to the nutritionist doctor.
Concerning vegan diet, Dr. Lecerf describes it as “more complicated to manage” because of the risk of calcium, zinc, iron, selenium or iodine deficiency. But these different elements also exist elsewhere, such as calcium in mineral water. On the other hand, so-called “bio-assimilable” vitamin B12, that is to say the one that our body is able to assimilate, comes only from animal products. and synthesis by bacteria. “The one found in seaweed like spirulina no use ! “, he warns. The deficit, which only sets in after four years, causes cognitive impairments. Vegans should therefore take vitamin B12 as a supplement, ensuring its origin.
Vegetarian or vegan, it is advisable to combine various protein sources: cereals (rice, bread, semolina) and legumes like lentils and beans. The whole then provides all the building blocks of our proteins – the amino acids – including those that our body does not know how to synthesize itself, called “essential”. the plant world offers other beneficial components, such as antioxidants and fiber, which meat buffs need too!
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