Tuesday, October 13, 2009

Red Meat > Fat > Colorectal cancer?

I was alerted by google news to an article on the "5 healthiest Meats". The article begins with a statement about a recent study showing increased risk of colon cancer in those eating red meat compared to those do not eat red meat. The article then summarizes the "five healthy meats that won’t wreak havoc on your colon". The article gives no review of how these meats are related to risk of colon cancer but only discusses percent fat in each. Wait what? Where in the article did the author state a connection between dietary fat and risk of colon cancer? What absolute lazy science reporting. Five minutes with google scholar and the author could have written a much more informative article.

The link between red meat and colon cancer is decades old and reviews of the evidence suggests a cautiously solid association. The association quickly led to the hypothesis that high dietary intake increases risk of colon cancer but recent reviews of both prospective and intervention studies do not support the hypothesis that high dietary fat increases risk of colorectal cancer. Interestingly, at least one intervention study found no decreased risk of colorectal cancer over a 10 year period after replacing meat with vegetables in the diet.

The news article highlights the poor training of science journalists. The biomedical literature highlights the difficulty in assessing causation in complex functional systems.

A good review is:
Diet, nutrition and the prevention of cancer
Timothy J Key, Arthur Schatzkin, Walter C Willett, Naomi E Allen,
Elizabeth A Spencer and Ruth C Travis
Public Health Nutrition: 7(1A), 187–200