The Canadian Cattlemen’s Association has reviewed the monograph, Carcinogenicity of consumption of red and processed meat as published in The Lancet, which summarizes the International Agency for Research on Cancer (IARC) review of red meat and processed meats. The Working Group charged with the review classified consumption of red meat in Group 2A, or “probably carcinogenic to humans,” which refers to a degree of certainty of causation. It is important to note that IARC conducts hazard assessments, not risk assessments. That means it considers whether meat at some level, under some circumstance could pose a risk. IARC has found hazards in about half of the agents it has reviewed.
In reaching the 2A classification, the Working Group’s review of 800 existing epidemiological studies from around the world “concluded that there is limited evidence in human beings for the carcinogenicity of the consumption of red meat,” and that “… no clear association was seen in several of the high-quality studies and residual confounding from other diet and lifestyle risk is difficult to exclude.”
The IARC monograph reported that colorectal cancer was its principle focus relative to red meat and that “a meta-analysis of colorectal cancer in 10 cohort studies reported a statistically significant dose-response relationship, with a 17 per cent increased risk (95 per cent CI 1·05–1·31) per 100 grams per day of red meat.” The American Society of Clinical Oncology has estimated that “a person with an average risk of colorectal cancer has about a five per cent chance of developing colorectal cancer overall.”
By this estimate, consuming 100 grams per day of red meat would increase the risk of colorectal cancer by just under one per cent in absolute terms. The meat industry has previously estimated that, on average, Canadians consume approximately 50 grams of fresh red meat or half this amount. Accordingly, if there is an increase in the potential risk of colorectal cancer from red meat consumption, by these estimates it is small and must be considered relative to the very significant nutritional benefits that red meat provides.
While meat’s very significant nutritional benefits are not considered directly in the IARC evaluation, it did note that “red meat contains high biological value proteins and important micronutrients such as B vitamins, iron (both free iron and haem iron), and zinc.”
The World Health Organization has previously stated that two billion people — over 30 per cent of the world’s population — have anemia, many due to iron deficiency. Beef is among the best food sources of well-absorbed iron. Meat has long provided an important source of nutrients for Canadians and the industry takes pride in providing high-quality beef products to consumers.
There are many theories why red and processed meat may be linked to cancer, however, it’s important to note that no scientific consensus has been reached.
Canadians hear a great deal about what foods we should eat and the perspective from the scientific community can change over time. Certainly cancer is a complex disease with many contributing factors including age, genetics, and lifestyle.
As with so many aspects of daily life achieving the right balance for your individual circumstance is key and we continue to recommend to Canadians that they follow the Government of Canada’s Food Guide.