Red meat, vegetables and colon cancer ; or is it the fish?

Epocrates, an online and smartphone medical app popular with physicians, recently reported Information published in NEJM Journal Watch (New England Journal of Medicine)

“Vegetarian Diets Are Associated with Lower Risk for Colorectal Cancer”

It has been recognized that high red meat consumption is associated with increased risk for colorectal cancer (CRC), and high fiber intake is associated with lowered risk; however, the effect of various types of meatless or vegetarian diets is less clear. In this North American prospective study, researchers identified dietary patterns and CRC occurrence in nearly 78,000 adults who were followed for a mean of 7 years, during which 490 cancers developed.  A prospective study is one in which the people studied are followed or observed over a continuing period of time, usually years.

Participants were characterized, based on food frequency questionnaires, as following one of five diets:

  • Vegans: No eggs, dairy, fish, or meat
  • Lacto-ovo vegetarians: Eggs and dairy, but no fish or meat
  • Pescovegetarians: Eggs, dairy, and limited fish, but no meat
  • Semivegetarians: eggs, dairy, and limited fish plus meat (≤1 time per week)
  • Nonvegetarians: eggs, dairy, and fish plus meat (>1 time per week)

After adjusting for certain personal and clinical factors, they reported that all four vegetarian groups had a 22% lower risk of colon cancer than nonvegetarians. Most impressive was a 43% lower risk for the pescovegetarians.

They concluded that any diet in which fruit and vegetable intake is emphasized has health benefits, including lower risk for CRC in certain circumstances. And that eating fish in particular may be even more beneficial in regard to colon cancer.

Vegetarian diets are popular for various reasons, some related to health, some related to concern for animals or the environment. Most physicians and laypersons believe there are health benefits although proving such is difficult. Documenting a person’s diet for any length of time relies on self-reports which may be inaccurate or even inflated. To compare vegetarians to nonvegetarians requires people to voluntarily eat  meat ,  since to request that someone subject themselves to a diet high in red meat would be unethical, given that we believe it is not healthy (even without hard proof).

I believe that an important point of this report is that this does not “prove” that red meat causes colon cancer or that eating vegetables prevents it. These diets seem to be associated with a higher or lower, respectively, risk of this cancer, but the specific relationship is still unknown, and may remain so for a long time.

In any event, I can still claim this is a good reason to eat more watercress. (laugh)

Epocrates also provides a free on-line data base on medical conditions written for non-healthcare professionals.

Here’s some additional information about colon cancer.

via Colorectal Cancer | Overview.