Does red meat cause cancer?
This week, the Word Health Organization (WHO) released a report ranking processed meat as “group 1: carcinogen to humans” and red meat in general as “group 2A: probably carcinogenic to humans”. Every media outlet in the world made headlines with this press release. At the one extreme, vegetarians around the world felt redeemed, and as you might expect at the other side of the spectrum, the meat industry reacted with skepticism.
As a cancer researcher from Argentina (a country alongside Australia and the USA as one of the highest red meat consumers) I was particularly interested in this news. When I grew up, we consumed beef almost on a daily basis. I found the article from the Guardian particularly good. The headline however was quite sensationalist: “Processed meats rank alongside smoking as cancer causes – WHO”. As is usually the problem with headlines, the article is, in complete contrast, well balanced and the information within the body is extensive and accurate. It’s such a common issue that “Don’t stop at the headline” was our very first How to “Research the Headlines” tip, and is the basis of our current Rewrite the Headlines competition with primary school children!
So what did the research say? There was an accompanying article from the International Agency for Research on Cancer in the prestigious medical journal The Lancet. The article cites epidemiologic studies that concluded that a daily consumption of 50 g of processed meat results in an 18% increased risk of developing colorectal (bowel) cancer. In countries with low meat intake, such as India, there are low rates of colorectal cancer, although this could be ascribed to anti-inflammatory spices utilized in these diets rather than to the absence of meat. There are also causal studies in animal models and rectal biopsies from humans indicating that certain red meat components – N-nitroso-compounds (or NOC), haem iron and polycyclic aromatic hydrocarbons (or HAA) – result in mutagenesis or aberrant gene expression that is linked, in turn, to cancer development or progression.
The key issue to stress is that, despite processed meat being ranked alongside tobacco smoking as a group 1 carcinogen, it does not mean that it is equally dangerous. Smoking accounts for the deaths of one million people per year worldwide, while about 34,000 deaths could be attributed to diets high in processed meat.
The problem with these headlines is that the public tends to ignore the probabilistic nature of this information and take it in absolute terms. I met some smokers who reacted happily to the former headlines that cancer is primarily caused by chance (“if it is just ‘bad luck’, why then to stop smoking?”) and meat producers stating that they “know people who eat a lot of meat and are 90”.
People could became so alienated with the concept that so many factors are carcinogenic that they might choose to ignore this information altogether. Instead, it seems a good advice to curb red meat intake to a few portions a week, not only to reduce risk of cancer, but also cardiovascular disease and diabetes. A good healthy life includes sun exposure in moderate amounts (which will not cause skin cancer), weight control and exercise, but we can still contemplate indulging with alcohol and red meat consumption in moderate amounts. Sausages, bacon, etc. should not be demonized, but enjoyed responsibly.
Bouvard, V. et al. (2015). Carcinogenicity of consumption of red and processed meat. The Lancet Oncology. DOI: 10.1016/S1470-2045(15)00444-1