Vegetarian Diets Are Associated with Lower Risk for Colorectal Cancer
In an observational study, no red meat consumption conferred CRC benefit.
High red meat consumption is associated with excess 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 cohort study, researchers identified dietary patterns and CRC incidence in nearly 78,000 adults who were followed for a mean of 7 years, during which 490 CRCs developed. 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)
In analyses adjusted for demographic and clinical factors, relative risk for CRC was 22% lower in all four vegetarian groups combined than in nonvegetarians. The only subgroup that showed a significantly lower relative risk when compared with nonvegetarians was pescovegetarians (43%); however, the sample sizes for individual vegetarian subgroups were small, and the confidence intervals were wide.
The subgroup data are most interesting here: Consumption of fish, in combination with lack of other meat consumption, might be what actually confers benefit. But the main finding is that any diet in which fruit and vegetable intake is emphasized has health benefits, including lower risk for CRC in certain circumstances.
Thomas L. Schwenk, MD reviewing Orlich MJ et al. JAMA Intern Med 2015 Mar 9.
Information sourced from NEJM Journal Watch
Orlich MJ et al. Vegetarian dietary patterns and the risk of colorectal cancer. JAMA Intern Med 2015 Mar 9; [e-pub].
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