Figure 3. Non-linear dose-response meta-analysis of red and processed meats consumption and the risk of colorectal cancer
Source(s): Chan DS, Lau R, Aune D, et al. Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies. PLoS One 2011; 6: e20456.
This week, the International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization (WHO), released a long-overdue monograph1 affirming the link between meat consumption and cancer risk. After reviewing more than 800 studies, the IARC decided to classify processed meat as a known carcinogen (Group 1), and red meat in general as a probable carcinogen (Group 2A). The agency urged public health officials to re-examine their dietary recommendations. Those anticipating the Canadian media to objectively inform the public of the news and start a rational dialogue may have been disappointed.
A news segment by Canada’s national broadcaster interviewed a cattleman who viewed the report as “an attack“ on his industry. The reporter referred to it as an “added hit” to declining beef and pork sales before queuing up a spokesman for the Canadian Cattlemen’s Association. He urged Canadians to ignore the findings and follow Canada’s Food Guide recommendations, as did the family physician who closed the segment.
Canada’s ‘national newspaper’ fared no better. It published an editorial that was criticised by readers for insulting their intelligence, and a column by its public health reporter that urged readers to ignore the supposedly misleading report – even as it misrepresented its content.
Contrary to what was written in the referenced column, the IARC did not find that “eating more than” 100 grams of red meat or 50 grams of processed meat daily increased colorectal cancer risk by 17 or 18 per cent, respectively. That would imply the stated consumption levels were ‘safe’. The IARC in fact issued a Q&A with the release to clarify that “risk increases with the amount of meat consumed, but the data available for evaluation did not permit a conclusion about whether a safe level exists.”
The relative risk mentioned in the review could be extrapolated to mean a person consuming say 200 grams of processed meat per day could double their relative cancer risk, since risk is compounded (i.e., 1.18^[200/50]). For reference, in 2012 the average Canadian’s lifetime cancer risk was nearly 30 percent; prostate and colorectal cancers – the primary forms affected by meat consumption, according to the IARC – accounted for 35 percent of cancer prevalence.2
The meta-analysis specifically cited by IARC3 found the risk associated with consuming both processed and red meat together rose non-linearly, as illustrated in the attached chart. Unfortunately, the meta-analysis did not provide separate estimates of relative risk for red and processed meat consumption, nor did it provide estimates for higher combined red and processed meat consumption levels (above 180g).
So where does Canadian meat consumption stand, and how does it square with Canada’s Food Guide recommendation?
According to the same source cited by IARC4, in 2013 the average Canadian consumed more than 250 grams of meat per day, of which 150 grams was red (bovine, pig, mutton and/or goat) meat.
The Canadian Food Guide actually has no guideline on red meat consumption. While the guide encourages Canadians to “select lean meat and alternatives prepared with little or no added fat or salt,” there’s no recommended upper-limit on red or processed meat consumption. Adults are advised to limit daily meat consumption to 2 portions for women, 3 for men. A portion is defined as 75 grams of any type of meat, fish, poultry or shellfish, including processed meats.
So an average male limiting his consumption to 225 grams of processed meat per day would be eating healthfully according to Canada’s Food Guide. Yet according to the IARC, that same dietary choice would significantly increase his relative risk of developing cancer. Hence the agency’s recommendation for public health officials to review their dietary recommendations.
Corporate/business interests aside (topic for another day), why was the national media in Canada so quick to downplay the IARC findings? Well, the title of the referenced Globe column, “Go ahead, have that BLT for lunch,” is telling. As the old saying goes, people like to hear good news about their bad habits. If they can’t get good, they’ll settle for less bad.
Unfortunately, that adage applies to the IARC review as well. In addition to downplaying the causal relationship between red meat consumption and cancer, the report also included a curious statement about how “red meat contains high biological-value proteins and important micronutrients such as B vitamins, iron (both free iron and haem iron), and zinc.”
If that sounds like a line out of a meat industry playbook, that’s because it is. While the scientists on the IARC Working Group had no conflicts of interest, the review’s ‘observers’ were almost all representatives from the meat industry.
That line about the nutritive value of meat could confuse readers into thinking that certain nutrients could only reliably be obtained from meat, which simply isn’t true. Calorie for calorie, whole plant foods are far more nutrient dense. The only exception would be vitamin B12, which is not naturally abundant in most plant foods. But neither is it naturally abundant in meat; in fact most of the vitamins found in Alberta beef, for example, are supplementally added to cattle feed. It would be safer and more cost effective for consumers to supplement directly.
The reason cattle feed requires supplementation is that animals in industrial feed lots – which account for practically all meat produced and sold in Canada – are neither fed their natural diets nor otherwise raised naturally, nor in most instances humanely.
It’s also worth noting that, whether it’s the UN Food and Agriculture Organization or the US Environmental Protection Agency, there is a growing consensus that livestock account for most of the greenhouse gas emissions caused by human activity.
So reducing meat consumption is better for human health, better for the animals and better for the environment. Understandably, people are reluctant to change their habits. And there are always corporate interests involved in sustaining the otherwise unsustainable status quo.
Then again, it wasn’t that long ago that the medical community and popular media actively promoted the health benefits of smoking. Their reluctance then to confront corporate interests resulted in needless illness and early death from smoking-related illnesses, and needless burden on health care systems, for decades.
As with smoking, the scientific community has grudgingly started to turn the corner on meat consumption after decades of research sounding the alarm. Hopefully, the Canadian media will come around sooner rather than later.
1. Bouvard V, Loomis D, Guyton KZ, et al on behalf of the International Agency for Research on Cancer Monograph Working Group. Carcinogenicity of consumption of red and processed meat. The Lancet Oncology, published online October 26, 2015.
2. International Agency for Research on Cancer. GLOBOCAN 2012: Estimated cancer incidence, mortality and prevalence worldwide in 2012.
3. Chan DS, Lau R, Aune D, et al. Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies. PLoS One 2011; 6: e20456.
4. Food and Agriculture Organization of the United Nations Statistics Division. Food Balance, 2013.