It would be easy to infer from headlines on many news articles that eating red meat increases the risk of developing colon cancer. For example, "Red Meat increases Colon Cancer Risk," states one, while another trumpets "Red meat newly linked to colorectal cancer."
In fact, the story is significantly more nuanced than such headlines (and many of the associated articles) make it seem.
The source of the furor was a report published in the Journal of the American Medical Association (Chao A ,Thun MJ, Connell CJ, McCullough ML, et al. Meat consumption and risk of colorectal cancer. JAMA 2004;293(2):172-182). It described the results of a major epidemiologic study by researchers associated with the American Cancer Society and Emory University.
Nearly 150,000 adults between the ages of fifty and seventy-four provided information on questionnaires about their food intake and health in 1982, and again in 1992 and1993. They then provided updated information every two years between 1997 and 2003 by means of additional questionnaires.
It is true that the initial analysis of the data indicated a significant positive association between high consumption of red meat and the risk of cancer of all parts of the colon (large intestine). But what the news writers didn't point out is that when other factors that could influence the appearance of colon cancer were taken into account, the association with high red meat consumption was no longer significant. These other factors included body mass index, cigarette smoking, physical activity, aspirin use, and alcohol consumption.
So does that mean there's nothing to the story of a connection between red meat and colorectal cancer? Not quite. The researchers did find a significant link between high red meat consumption and cancer of the distal colon (the part closest to the rectum) in people who reported the highest consumption in both 1982 and 1992 and 93: the risk was increased by 50%. In addition, people who had the highest intake of red meat in only the later questionnaires had a 70% increased risk of developing rectal cancer.
These statistics are enough to concern anyone -- but they really should not concern people who follow intake recommendations like the federal Dietary Guidelines for Americans. The increased risks were seen in people whose intakes were very high. The men in the highest intake group reported, on average, eating over three pounds of red meat per week, and the women in that group consumed over 1.5 pounds per week. In contrast, current recommendations for adults are to consume up to forty-two ounces of food from the meat, poultry, fish, egg, and dried beans food group per week. This does not mean that the entire forty-two ounces should come just from red meat -- one of the major underlying principles of the Guidelines is the importance of choosing a variety of foods from each of the food groups.
So, what are the take-home messages from this research? First, this is an epidemiologic study -- one that can find associations between various factors, but cannot necessarily attribute causation. Therefore, consumers should not rush to conclude that red meat consumption is "bad." Second, people whose meat intake was moderate did not experience the significantly increased risk of colorectal cancer. Thus, this study supports the old truism recommending dietary moderation and variety.
Ruth Kava, PhD., R.D., is Director of Nutrition at the American Council on Science and Health.