by Reed Mangels, PhD, RD

A recent study examined the association between a vegetarian diet, as compared to a nonvegetarian diet, and the risk of different types of cancer. This study included almost 80,000 Seventh-day Adventists living in the United States and Canada and was part of a larger study called the Adventist Health Study-2 (AHS-2). Study subjects completed extensive questionnaires about their food choices and their health. They were followed for an average of 7.9 years. During that time, records were kept of all new cancers that were diagnosed in study participants based on state cancer registries and medical records.

The researchers used the participants’ dietary information to categorize participants as vegans (consumed any animal product less than once a month), lacto-ovo vegetarians (no flesh foods; consumed dairy and/or eggs once a month or more), pesco-vegetarians (similar to lacto-ovo vegetarians but ate fish once a month or more), semi-vegetarians (ate flesh foods less than once a week but at least once a month), and nonvegetarians. For this study, the “vegetarian” group included vegans, lacto-ovo vegetarians, and pesco-vegetarians.

Compared to similar-aged nonvegetarians, younger vegans had a lower risk of both breast cancer and prostate cancer. Both younger and older vegans had a lower risk of lymphomas (cancers of the lymphatic system).

“Vegetarians” had a lower risk of cancer in general as well as a lower risk of stomach cancer, colorectal cancer, and lymphoma compared to nonvegetarians. There was a possibility that “vegetarians” also had a reduced risk of pancreatic, lung, and ovarian cancer but the study was not large enough to make definitive conclusions about these kinds of cancer. Not every type of cancer appears to be affected by diet; cancers of the nervous system, the uterus, and myeloid leukemia did not appear to be associated with diet.

The results showing a lower risk of certain cancers in “vegetarians” and vegans are especially interesting when we note that the nonvegetarian comparison group, because they were Adventists, are relatively health conscious and consume low amounts of meat. Results might differ even more if the comparison group was eating a more typical American diet. Also interesting is that there was “no clear indication” of a higher risk of any cancer in the “vegetarian” group.

Reference

Fraser GE, Butler FM, Shavlik DJ, et al. Longitudinal associations between vegetarian dietary habits and site-specific cancers in the Adventist Health Study-2 North American cohort. Am J Clin Nutr. 2025;122(2):535-543.