Are red meats dangerous?
On Oct. 26, 2015, the cancer agency for the World Health Organization (the International Agency for Research on Cancer or IARC) placed red meats and processed meats into their group system that lists cancer-causing agents. The IARC consists of 22 experts from 10 countries. Cancer-causing agents are referred to as carcinogenic agents. This grouping of carcinogenic agents is based on evidence either that they can cause cancer (group 1) or that they probably can cause cancer (group 2A) in humans. This has caused quite a stir in many arenas, especially the beef-producing companies.
What are red meats?
Of note, the term red meat refers to all types of mammalian muscle meat such as beef, pork, veal, lamb, mutton, horse, and goat. Consequently, the term red meat, when used by the IARC, does not mean a stage in cooking where meat is marginally cooked or grilled, so it does not matter if the meat is cooked "rare" or "well done." Also, the term processed meat refers to any meat that has been treated or transformed by salting, curing, smoking, fermentation, or other processes to improve meat preservation or to enhance the flavor of meats. Most processed meats contain beef or pork that may also contain other mammalian meats and/or poultry, offal (entrails and/or animal internal organs), or meat byproducts (for example, blood, fats). The IARC gives examples of such processed meats; they include hot dogs, sausages, corned beef, beef jerky, canned meat, and meat-based preparations and sauces.
The IARC listed processed meat as "carcinogenic to humans" (group 1) for colorectal cancer and further stated their decision was based on sufficient evidence from research studies in humans. The experts at IARC suggested that a 50 g portion of processed meats (4 strips of bacon or one hot dog) eaten daily increases the lifetime risk of colorectal cancer by about 18%. That means your risk of developing colon cancer increases from 5 to 5.9% over your lifetime.
For red meats, the IARC classified them as "probably carcinogenic to humans" (group2A) and base their conclusions on more limited evidence for development of colorectal cancer, but pancreatic cancer and prostate cancer may also be linked to red meat consumption. The IARC indicated the consumption of 100 g of red meat daily increases the risk of colorectal cancer by 17% over your lifetime. That means that your risk of ever getting colorectal cancer increases from 5 to 5.85% over your lifetime.
The data for these IARC classifications is based on more than 800 studies investigating associations of many types of cancer with the consumption of red meat and processed meat in many different countries with populations having diverse diets. Unfortunately, the cancer risks of consuming only poultry or fish were not included in the studies, nor were vegetarian diets studied.
The meat industry considers the data and IARC report as biased and misleading. For example, the North American Meat Institute and the National Cattlemen's Beef Association both considered the conclusions as "tortured data" and said the report neglected to comment on scientists at the IARC who reportedly did not agree with the groupings.
How much red meat should I eat?
So what am I going to do as a physician when patients ask about what they should do about eating red meat and/or processed meats? First, I would suggest that a healthy diet be consumed and would suggest that a reduction in red meats in the diet may be warranted. Also, I would suggest markedly reducing or eliminating processed meats.
Am I completely buying into the IARC report? The answer is that I've recommended this type of low meat diet for a few years because other good independent studies have also made similar recommendations. For example, the China study provided information about the relationship between diet and the occurrences of coronary artery disease and cancers. In addition, I would refer the patients to dietary guidelines provided by the American Heart Association and the American Cancer Society, as their recommendations are similar. What the IARC has done has simply stated in very clear terms (based on recently accumulated data) that there is a risk of colorectal cancer related to red meats and processed meats. This press release appears analogous to the announcements made by the American Cancer Society and many doctors when they concluded that cigarette smoking posed a higher risk for lung cancer (and eventually other cancer types).
Medically reviewed by Jay B. Zatzkin, MD; American Board of Internal Medicine with subspecialty in Medical Oncology
American Cancer Society. "ACS Guidelines on Nutrition and Physical Activity for Cancer Prevention." Apr. 9, 2015. <http://www.cancer.org/healthy/eathealthygetactive/
Campbell, Thomas, and T. Colin Campbell. The China Study: The Most Comprehensive Study of Nutrition Ever Conducted And the Startling Implications for Diet, Weight Loss, And Long-term Health, 1st Ed. Dallas, TX: BenBella Books, 2006: 417.
France. International Agency for Research on Cancer (IARC). World Health Organization. "Press Release No. 240: IARC Monographs Evaluate Consumption of Red Meat and Processed Meat." Oct. 26, 2015. <http://www.iarc.fr/en/media-centre/pr/2015/pdfs/pr240_E.pdf>.