A study by the University of Stanford (USA), published in the journal Plos Climate, he tried to imagine a world without meat, eggs and dairy products. And in 28 pages full of graphs, calculations and tables, he launched a provocation: if all the farms in the world suddenly disappeared, and a third of the crops needed to maintain them were reconverted into forests, the problem of climate change would be largely solved.
In a somewhat brazen way, the researchers have not in the least taken into account the consequences that such a drastic choice would have on society, the economy and health. Their goal, in fact, was to confront us with a fact: our consumption of meat is unsustainable. They did it by playing the bass drum, but the environmental impact of what we bring to the table has been in the spotlight for over a decade.
Farms and environment: some data. Intensive farming contributes approximately 14% to total greenhouse gas emissions, and as much as 40% of cultivated land provides products for livestock. If we put the mammals of the entire planet on a scale, cattle and pigs alone would account for 60% of the weight, while chickens and other domestic birds make up 70% of the biomass of all birds. And a study by the Institute for Climate Research in Potsdam (Germany) estimated that if by 2050 20% of beef were replaced with an already available alternative product, obtained from mushrooms, deforestation and the CO2 emissions associated with its production, and methane pollution, a powerful greenhouse gas produced by farms, would also drop by 11%.
Finally, a comparison between the impact of vegetarian and omnivorous diets – carried out in the USA as part of a very large study involving over 34,000 followers of the Seventh-day Adventists church – concluded that diets that include meat less of once a week require an average of 10,252 liters of water less than that needed to feed those who eat this food more often for seven days. The account was also made for the energy consumed (with 9,910 kJ saved in low-meat diets), for fertilizers (186 grams less) and for pesticides (5 grams less).
Eliminate meat altogether? In short, the arguments in favor of a diet that does not include farms are not lacking. But can we really eliminate an entire class of foods from our tables without affecting our health? «Foods of animal origin contain nutrients which, if not taken in adequate quantities, must be supplemented», explains Francesco Sofi, professor of Applied Dietetic Technical Sciences at the University of Florence.
Vitamin B12 is the most critical, because it is not present in plants, and is important for the production of red blood cells, for the duplication of DNA and RNA, and maintains a healthy nervous system.
For this reason, vegans, who exclude all products of animal origin from their diet, have to resort to supplements. Vegetarian diets that include milk and eggs, and the pescetarian diet, which also includes fish, do not have this problem. In fact, they contain everything the body needs and several studies have concluded that, from a health point of view, they are even advantageous, because they are linked to a reduction in mortality and a lower risk of contracting various chronic diseases. «After all», continues Sofi, «fruit and vegetables, abundant in these diets, are rich in vitamins and other chemical substances that are certainly beneficial. While the excessive consumption of red meat (especially processed salami, sausages, etc.) is a risk factor for tumors ». The matter would seem to be closed here. But going a little deeper, a more complex picture emerges.
Difficulties in studies. “Research comparing vegetarian and omnivorous diets presents some problems,” explains Sofi. “The American ones, which show the greatest benefits, are not very representative of our reality, because there omnivores eat really badly and eat very large quantities of meat”. Not only. «Almost all the studies (thus including the European ones) are of an observational nature: that is, they have followed very large groups of people over time, relating the incidence of various diseases to eating habits, measured through questionnaires. The problem is that these measurements cannot be precise. The occasional consumption of meat and exceptions to the rule, for example, are not taken into account».
Cancer risk. Sometimes, then, we don’t even consider any changes in eating habits that occurred after the start of the study. Finally, it is often difficult to separate the effect of diet from that of other lifestyles, even if we try to take them into account in the calculations. For example, a research published on BMC medicine, conducted in the United Kingdom with the criteria set out above, found a reduced risk of getting various cancers among vegetarians and pescetarians. And yet, the same authors admit that the advantages observed «could depend on the diet but also on different lifestyles, and in particular on the fact that vegetarians and pescetarians tend to smoke less».
Net of these limitations, however, the benefit on the incidence of tumors seems confirmed, with a more marked effect for colon and prostate cancer.
Some observational studies have also found a protection of vegetarian diets against the cardiovascular system, linked to a lowering of risk factors such as hypertension, blood sugar and cholesterol levels. The effect is more pronounced for pescetarians, with a drop in heart attack mortality of up to 35%. “It is a fact that makes sense, because it is known that the omega-3 fats in fish protect the heart,” observes the expert.
Protect the heart. On lacto-ovo vegetarian diets, on the other hand, Francesco Sofi’s group is conducting a research called Cardiveg which intends to smooth out the many uncertainties linked to previous studies and lowers the results into the Italian reality. “We asked two groups of volunteers, both previously omnivores, to follow a lacto-ovo vegetarian or Mediterranean diet for three months.” The two diets, precisely indicated by the researchers, both included large quantities of fruit and vegetables, and differed in a higher content of dairy products and legumes in the vegetarian diet and the presence, in the Mediterranean diet, of 350 grams of meat and 375 grams of fish week.
The Mediterranean diet. Even if the scheme does not allow to evaluate the long-term effect, three months were enough for both groups to lose some weight. Furthermore, the vegetarian diet reduced blood cholesterol, while the Mediterranean diet was better at controlling triglycerides (another important cardiovascular risk factor). Finally, vegetarians have been found to have a low level of vitamin B12. “The data did not surprise us, and indicates that even those who follow the lacto-ovo vegetarian diet must control this vitamin,” explains Sofi.
Finally, the researchers evaluated another key element for the health of the heart and vessels: the presence in the blood of stem cells derived from the bone marrow. In addition to being the progenitors of white and red blood cells, these cells are involved in the repair of any damage that may be present on the vessel walls. So much so that, we read in the article published on Nutrition, Metabolism & Cardiovascular Diseases, “we are thinking of using them as an indicator of cardiovascular risk”. Regarding the results of the study, it emerged that the Mediterranean diet causes a significant increase in circulating stem cells, while a reduction is observed among vegetarians.
The reasons are not clear and the result needs to be confirmed by larger studies. Researchers hypothesize that the cause of the phenomenon may be low levels of vitamin B12, or the fact of not eating fish.
for our planet. For all these reasons, the guidelines for healthy eating, developed in various countries, generally do not recommend eliminating meat altogether. Rather, the indication is to strongly limit its consumption which, at least in Western societies, is excessive and far from healthy. Even more complex is balancing the knowledge acquired in the medical field (and still incomplete) with environmental needs.
Summing up, already in 2019, was a commission of the medical journal Lancet, created precisely with the aim of indicating a useful strategy for achieving sustainable food production for the environment and at the same time adequate to support the world population , in accordance with the objectives defined by the United Nations 2030 Agenda and the Paris Climate Agreement. The proposed diet consists largely of fruit, vegetables, whole grains and legumes. It also includes fish and chicken, and very low amounts of red meat and added sugars. According to the commission’s forecasts, this scheme is capable of adequately feeding 10 billion people, while also remaining within the boundaries of safety for the environment.