Study: Vegetarian diets linked to lower risk of several cancers

LOMA LINDA, Calif. — A new longitudinal study has found that vegetarian diets are associated with a lower risk of several types of cancer, including less common cancers such as stomach and lymphoma. The research, published this month in the American Journal of Clinical Nutrition, analyzed cancer incidence among nearly 80,000 North American Seventh-day Adventists and found a 12% overall reduced risk of all cancers among vegetarians.

“This is the first study with strong information and sufficient precision to report on the association between various vegetarian diets and the risk of some less common cancers,” said lead author Dr. Gary Fraser, MBChB, Ph.D., of Loma Linda University.

According to the study, vegetarians had a 45% lower risk of stomach cancer and a 25% lower risk of lymphomas compared to their non-vegetarian counterparts. Vegans, specifically, showed approximately 25% lower risk of both breast and prostate cancers. The study also found a 20% reduction in the risk of colorectal cancer among those following a vegetarian diet.

“This is all relatively unique information and possibly the most robust that’s out there concerning cancers such as stomach and lymphoma,” Fraser said. “It may also be pointing the finger at several other cancers — such as lung, ovary and pancreas — where the evidence from this study was suggestive of lower risk in vegetarians, but did not quite reach the necessary standard to say more.”

The study did not find evidence that vegetarian diets offered protection against uterine cancer, myeloma, myeloid leukemias or cancers of the nervous system.

Researchers used data from the Adventist Health Study-2, which enrolled nearly 96,000 participants between 2002 and 2007 and tracked cancer incidence through 2015. About half of the study participants identified as vegetarian. The study cohort, largely made up of Seventh-day Adventists living in the United States and Canada, has been used in more than 200 peer-reviewed studies examining diet, health and disease.

Funding for the study was provided by Loma Linda University, with earlier funding for cohort establishment from the National Cancer Institute and Britain’s World Cancer Research Fund.

Fraser noted that comparing vegetarian Adventists to non-vegetarian Adventists—who are still generally health-conscious—means the protective benefits of plant-based diets might be even greater when compared to the general population.

“In some ways, it’s amazing that we found anything at all,” Fraser said. Previous comparisons show that non-vegetarian Adventists have about a 25% reduction in overall cancer risk compared to the general U.S. population, while vegetarian Adventists have around a 35% reduction.

Among vegetarian diets, the study found that vegans generally experienced the most benefit. However, one exception was noted: pescatarians had a lower risk of colorectal cancer compared to other vegetarian groups.

The full study is titled “Longitudinal Associations Between Vegetarian Dietary Habits and Site-Specific Cancers in the Adventist Health Study-2 North American Cohort.”