Could Vegetarian Diet Lower Colorectal Cancer Risk?

A new study finds a link between a vegetarian diet and a reduced risk of developing colorectal cancer.

In an effort to evaluate the association between vegetarian dietary patterns and incident colorectal cancers, a team led by Loma Linda University researchers analyzed 77,659 men and women who were recruited to the Adventist Health Study 2 (AHS-1) between 2002 and 2007.
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The investigators assessed participants’ diet at baseline via a validated quantitative food frequency questionnaire, establishing 4 vegetarian dietary patterns—vegan, lacto-ovo vegetarian, pescovegetarian, and semi-vegetarian—and a non-vegetarian dietary pattern. The authors identified colorectal cancer cases primarily by state cancer registry linkages. During a mean follow-up period of 7.3 years, the team documented 380 cases of colon cancer and 110 cases of rectal cancer.

Compared with those not following a vegetarian diet, participants who ate a vegetarian diet were at a 22% lower risk of colorectal cancer, and a 19% reduced risk for colon cancer and a 29% lower risk of rectal cancer. More specifically, pescovegetarians were at a 49% lower risk for colorectal cancer, while lacto-ovo vegetarians saw an 18% reduced risk, and vegans were at a 16% lower risk. For semi-vegetarians, that number stood at 8%.

While screening efforts such as colonoscopies have helped save many lives by detecting pre-cancerous polyps and removing them, “primary prevention is even more important, and primary care practitioners can recommend dietary approaches to primary prevention,” says Michael J. Orlich, MD, PhD, program director, preventive medicine residency at Loma Linda University, and lead study author.

Prior evidence links eating red and processed meat to a higher risk of colorectal cancer and fiber-rich foods to a lower risk,” says Orlich. “In our study, people consuming healthy vegetarian diets (including vegetarians who ate fish) had a lower risk of colorectal cancer than non-vegetarians. 

The vegetarians in the Loma Linda-led study not only ate less meat than the non-vegetarians, but also consumed less sweets, snack foods, refined grains, and caloric beverages, he continues, noting that these participants ate more fruits, vegetables, avocados, whole grains, beans, and nuts.

“Emphasizing such healthy diets rich in whole plant foods, as well as low in red and processed meat,” says Orlich, “might help patients reduce their risk of colorectal cancer and other chronic diseases.”

—Mark McGraw

Reference

1. Orlich M, Singh P, et al. Vegetarian Dietary Patterns and the Risk of Colorectal Cancers. JAMA Intern Med. 2015.