Oftentimes, the WHO/IARC report on red and processed meats and cancer is cited by those advocating vegetarian diets for health improvement. Usually, however, it is ignored that this report identifies meat as a hazard and not as a risk (an important distinction, of which the importance is explained elsewhere on this website). But the problem runs deeper. After its release in 2015, the IARC report was criticized by leading scientists in the domain of evidence-based medicine. Guyatt and Djulbegovic argued that WHO was “doing the public a disservice” by providing misleading advice based on weak evidence. Various other scientists have published objections to dietary recommendations that discourage red meat intake, not only in response to IARC but also to similar guidance from the World Cancer Research Fund, Flemish Food Pyramid, and EAT–Lancet Commission.
In 2019, Guyatt and several colleagues entered the debate once again, but this time with a very comprehensive quality assessment of the evidence. In a series of articles, they applied the so-called GRADE system to assess the quality of the epidemiological data on red and processed meats, which turned out to offer only low- to very-low-certainty evidence (see video on top of the page). First, the absolute risk reductions in disease and mortality were exposed as trivial. For instance, the chance of not developing colorectal cancer decreases from 94% to 93% in a lifetime of high consumption of processed meats, which corresponds to an absolute risk reduction of only 1%. Second, such risks may as well be artifacts as the quality of the evidence needed to assume a causal relationship is low. At the same time, the data is at serious risk of bias and confounding (see also elsewhere). The authors concluded that there is no solid basis to restrict the consumption of red and processed meats below current intake levels for human health. A more recent GRADE-based study performed by other authors came up with a similar conclusion.
Interestingly, this evaluation led to a major controversy, involving aggressive reactions from anti-meat agendas. Although GRADE is a global system used by >100 organizations, the NutriRECS authors were viciously attacked following their evaluation. More specifically, the attack came from PCRM (an animal rights front) and the True Health Initiative (including EAT-Lancet’s lead author, Prof. Willett). Regretfully, both organizations tried to discredit the NutriRECS analysis by accusing its authors of conflicts of interest through an unfounded smear campaign of the pot-meet-kettle type, thereby attempting to pre-empt publication of the studies. Their main argument was that lower-quality standards should apply to nutritional epidemiology than other health domains, simply because it is more difficult to obtain quality evidence (as is explained elsewhere).
