Lower Colorectal Cancer Risk With Pescovegetarian and Vegetarian Diets

Vegetarians had a lower colorectal cancer risk

In a large study of more than 77,000 participants, it was found that those who ate a vegetarian diet had a lower risk of colorectal cancer compared with their meat-eating counterparts. The most risk reduction was associated with pescovegetarians-this group had a 43% relative risk reduction of colorectal cancer compared with non-vegetarians. Eating a vegetarian diet resulted in a 22% relative risk reduction of colorectal cancer compared with a non-vegetarian diet.

The results of the study were published in JAMA Internal Medicine.

Previous studies have found that dietary factors can influence colorectal cancer risk. The consumption of red and processed meat is linked to an increased risk of colorectal cancer, while dietary fiber consumption has been associated with a lower risk of this cancer.

Michael J. Orlich, MD, PhD, of the school of public health at Loma Linda University, and colleagues followed Seventh-Day Adventist men and women in North America who were included in the prospective cohort. The participants were recruited between 2002 and 2007. Out of a total of 77,659 participants analyzed, 380 cases of colon cancer and 110 cases of rectal cancer were identified during the follow-up period. The average follow-up time was 7.3 years. Compared with meat-eating participants, vegetarians had a 19% lower relative risk of colon cancer and a 29% lower relative risk of rectal cancer.

Vegans had a 16% lower risk of colorectal cancer compared with non-vegetarians, and lacto ovo vegetarians had an 18% risk reduction of colorectal cancer. Semivegetarians had an 8% lower relative risk of colorectal cancer compared with non-vegetarians.

The diets of the participants were assessed by the authors using a detailed questionnaire that included more than 200 foods at the start of study enrollment. Four vegetarian dietary patterns and 1 non-vegetarian dietary pattern were defined prior to the start of the study, and vegetarian vs non-vegetarian was defined based on the questionnaire answers. For example, pescovegetarians were defined as those who consumed fish one or more times per month but all other meats less than one time per month.

A total of 7,811 pescovegetarians, 5,861 vegans, and 22,424 lacto-ovo vegetarians were identified among the study participants.

Vegetarians tended to have a lower body mass index and to have a lower intake of total and saturated fat, as well as a higher intake of fiber.

According to the authors, a strength of the study was the inclusion of a diverse cohort of individuals that varied by age, sex, race, geographic location, and socioeconomic status, providing relevance to the findings for the general North American population.

But, because of the relatively early dietary follow-up of participants, the statistical power of the risk outcomes could be strengthened by later follow-up of the participants’ diet patterns. Still, the authors noted that the duration of adherence to the baseline diet was long among the participants-21 years for vegans and 39 years for lacto ovo vegetarians.

“The evidence that vegetarian diets similar to those of our study participants may be associated with a reduced risk of colorectal cancer, along with prior evidence of the potential reduced risk of obesity, hypertension, diabetes, and mortality, should be considered carefully in making dietary choices and in giving dietary guidance,” concluded the study authors. “If such associations are causal, they may be important for primary prevention of colorectal cancers.”