Vegetarianism Linked to Lower Risk of Colorectal Cancers

Lower incidence of colorectal cancer was found in Seventh Day Adventist patients eating a vegetarian diet, according to evidence published in JAMA Internal Medicine.

Michael J. Orlich, MD, PhD and researchers from Loma Linda University in California observed the diets of more than 77,000 Seventh Day Adventist men and women in order to evaluate the link between vegetarian dietary patterns and incident colorectal cancers. The participants were recruited between January 1, 2002 and December 31, 2007, and their follow up varied by state and was indicated by the cancer registry linkage dates. The analysis was conducted between June 1, 2014 and October 20, 2014. The researchers also factored in important demographic and lifestyles confounders.

After an average follow up period of 7.3 years, the researchers identified 380 cases of colon cancer and 110 cases of rectal cancer among the participants. The vegetarians were broken down into 4 categories: vegan, lacto/ ovo vegetarian, pescovegetarian, and semivegetarian. The researchers found that black participants were underrepresented among all groups, except pescovegetarians. The vegetarians were more likely to have higher educational levels, to exercise, and use calcium supplements (except the vegan participants). The group overall was less likely to have ever smoked, drink alcohol, have had a colonoscopy or sigmoidoscopy (particularly the vegans, the researchers noted), to use aspirin or statins, to have diabetes treatment in the past year, or to have a history of peptic ulcers. The vegetarians were found to have lower body mass indexes (BMI) and lower intakes of total fat, saturated fat, total meat, red meat, and processed meat, though they had a higher intake of fiber.

The researchers also noted the vegans and semivegetarians had a lower dietary calcium intake. The semivegetarians notably had lower energy intake than the other groups, but were similar among the other 3 categories.

Colorectal cancer risk was reduced when linked to a vegetarian diet, the researchers found. This was also true when the analysis was conducted strictly for colon cancer. The analysis was conducted specifically for rectal cancer as well, but was limited by power and, thus, inconclusive, the researchers implied.

“Vegetarian dietary patterns in a large North American cohort, particularly the pescovegetarian dietary pattern, were associated with lower risk of all colorectal cancer as well as colon cancer separately,” concluded the authors. “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.”

The researchers also commented that this study was consistent with prior studies, which linked red meat and processed meats to increased risk of colorectal cancers. The researchers believed the results of this study were similar to other results because of the reduction in meat intake, but also as a result of the increase in whole plant foods consumption.