Bacon and cancer
The new classification of processed meat as
carcinogen to humans Group 1 by the World Health Organization
This week, bacon was in the news. It has been classified by the World Health Organization (WHO) as carcinogen to humans Group 1, together with tobacco smoking asbestos. People do love bacon. My daughter used to work in a cafe and she tells me that the customers would go to great lengths to describe the exact way they would like their bacon cooked. But she's a scientist now and has looked into this new classification for us. I hope that the following paragraphs help to explain the science and research behind the new classification and what it might mean for the bacon lovers among us.
THE NEW CLASSIFICATION
On the 26th of October, the World Health Organization issued a press release stating that processed meat was classified as Carcinogenic to Humans (Group 1) and that red meat was classified as Probably Carcinogenic to Humans (Group 2A). This meant that they had classed processed meats like bacon, salami, ham, frankfurters etc in the same cancer-causing class as tobacco and asbestos. Click here to view the press release
THE RESEARCH:
The new classification is based on the results of an evaluation by the IARC (International Agency for Research in Cancer). The IARC is part of the World Health Organization and its mission is "to coordinate and conduct research on the causes of human cancer, the mechanisms of carcinogenesis, and to develop scientific strategies for cancer control." 22 experts from 10 different countries met to evaluate over 800 studies published in the last 20 years. The group evaluated both red meat (beef, veal, pork, lamb, mutton and goat) that is generally cooked before eating and processed meat. Processed meat (such as bacon) refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation. It may contain red meat or also other meats, liver or meat by-products such as blood.
THE SCIENCE:
The research was published in The Lancet and is available to subscribers to download here. Here is a summary of the article:
Red meat has been known to have health benefits because of its protein and micronutrient (B vitamins and iron) content. Its fat content varies. Cooking red meat, particularly via high temperatures such as grilling, frying and barbecuing can produce cancer-causing chemicals called aromatic amines (HAA) and polycyclic aromatic hydrocarbons (PAH). The processing of meat (salting, curing, fermentation, smoking and others) can result in the formation of cancer-causing chemicals N-nitroso compounds and PAH.
200g of meat per day is considered 'high consumption.'
The study was an 'epidemiological' study: they evaluated data from populations. The studies they were most interested in were the prospective studies in the general population; these look at a population and see if there is an association between amount of red and processed meat consumed, and cancer incidence.
They found that the biggest concern was with colorectal cancer. Half of the red-meat studies found that a high consumption of red meat was associated with colorectal cancer occurrence whereas two thirds of the processed-meat studies found this association. Case studies were also evaluated, however these weren't given as much weight as the population-based studies.
There was so much consistent data associating the eating of processed meats with colorectal cancer, that chance, bias and confounding evidence were such unlikely explanations, that the group concluded "there is sufficient evidence in human beings for the carcinogenicity of the consumption of processed meat." In other words, eating processed meat causes colorectal cancer. With red meat, the evidence was strong but not as strong, so the conclusion was that there is 'limited evidence' that red meat is cancer-causing.
Placing processed meat in the same group as tobacco and asbestos does not mean that it is equally as dangerous. It means that the evidence which shows that processed meat is cancer causing, is as strong as the evidence which shows that tobacco and asbestos are cancer causing. 34,000 global deaths per year can be attributed to cancer caused by eating processed meat. 200,000 are caused by air pollution, 600,000 due to asbestos and 1 million due to tobacco smoke.
WHAT DOES IT MEAN?
The research group evaluates causes of cancer, but does not give recommendations. Their research may however be used by governments to produce policies to reduce cancer risk in the population. Genostics also does not give medical advice.
Red meat has many health benefits; it's a complete protein source and also contains valuable micronutrients. Overconsumption of red meat however increases the risk of cardiovascular disease due to its fat and sodium content. This new classification classifies red meat, either cooked at high temperatures or processed, as containing carcinogenic (cancer-causing) compounds.
There is no one diet that is right for everyone. Each person is totally unique and therefore his or her ideal diet will be completely individual. Many factors influence a person's ideal diet: allergies and sensitivities, demand, genetics, constitution, personal preferences, culture, availability etc to name a few. For advice on what you should and should not eat, please consult your medical or health practitioner. The WHO has also published a question and answer document, which you can find here.
If red meat is part of a person's diet, a healthy choice would be to consume it sparingly and to cook it slowly. Think slow roast lamb or slow-cooked goulash or stews.
Here's the latest 'food pyramid' guide to healthy eating produced by Harvard University. Clicking on the image will take you to the site. There's a lot of good information on it.
Image source: http://www.hsph.harvard.edu/nutritionsource/pyramid-full-story/