Lettre à l'éditeur de S. Gallus et C. Bosetti
The International Agency for Research on Cancer (IARC) in its recent Monograph Volume 114 has classified the consumption of red meat as “probably carcinogenic to humans” (Group 2A) and that of processed meat as “carcinogenic to humans” (Group 1). The unfavorable role of (red and processed) meat on cancer was already well-known to epidemiologists, nutritionists, and public health professionals, who have long been suggested to limit the consumption of red meat to no more than 300 g per week and avoid, as far as possible, that of processed meat.
Although it is important that this information reaches a more general public, the IARC evaluation of meat consumption was announced by mass-media and newspapers through sensational headlines, spreading a very different message: (processed) meat kills like tobacco smoking, also classified by IARC in Group 1. As an example, in Italy a single burned steak was considered equivalent to 600 cigarettes in terms of health risk! The confusion generated by the (mis)information of the lay-press may, in our opinion, have serious consequences, since it could: (i) over-estimate the health harms of meat, (ii) discredit the scientifically valid work of the IARC Working Group and, more importantly, (iii) reduce the public awareness of the harmful effects of tobacco smoking on human's health and consequently increase its social acceptability. In interpreting and disseminating the results of the IARC Monograph Volume 114, it is therefore crucial to underline that the risk of cancer in relation to meat is—both at an individual and at a population level—extremely limited as compared to that of (cigarette) smoking.
In order to clarify this point, we roughly estimated the absolute number of cancer deaths attributable to meat and that attributable to smoking in the Italian population. The IARC Working Group based its conclusions essentially on the direct association between meat and colorectal cancer, reporting an excess relative risk of 17% for each additional portion (100 g) per day of red meat and of 18% for an additional portion (50 g) per day of processed meat. Considering that in Italy the average per capita daily consumption of red meat is 61 g and that of processed meat is 27 g (i.e., approximately 60% and 55% of a conventional portion of red or processed meat, respectively), that excess risk translates into a fraction of colorectal cancers attributable to red meat of 10.4% and to processed meat of 9.7%. Again this corresponds to around 4000 annual colorectal cancer deaths (out of ∼22,000) attributable to the consumption of red and processed meat combined. Although the number of estimated cancer deaths attributable to processed and red meat consumption in Italy is considerable, it remains modest compared to that attributable to tobacco smoking. Indeed, in Italy, where average adult cigarette consumption is around 3 cigarettes per day, cancer mortality attributable to cigarette smoking has been estimated in about 36,000 annual deaths (of which 26,000 from lung cancer only).9 Forcing a comparison in terms of carcinogenicity, in the Italian population one single cigarette is equivalent to more than 3 average Italian daily portions of red or processed meat. Accordingly, the average yearly consumption of red or processed meat of the Italian population corresponds to 3 packs of cigarettes, only.
Another important issue to be considered is that the carcinogenic effect of meat consumption may be due to chemical substances (e.g., n-nitroso-compounds, polycyclic-aromatic hydrocarbons, and heterocyclic aromatic-amines) developed through meat processing, preservation and cooking but not to meat consumption per se. Indeed, several mechanisms related to these chemicals were considered as potential explanations for the association between meat consumption and cancer risk by the same IARC Working Group.Moreover, red meat or processed meat include a huge variety of very different items. It remains therefore debatable the opportunity to evaluate among potential carcinogens such as tobacco or chemical substances an entire food category as red or processed meat.