Because vegetarian diets are so high in fruit, vegetables, fiber, nuts, legumes and other healthy foods that prevent cancer and are devoid of meats and dairy that have been associated with cancer, there is a large body of evidence supporting vegetarian diets as preventative of cancer. Now there is a larger body of evidence.
This study included 79,468 Seventh-day-Adventists from Canada and the United States. Some of them were vegetarian and some were nonvegetarian. They were followed for an average of 7.91 years.
For every type of cancer, vegetarian diet either did no harm or did benefit. Overall, there was a significant 12% reduction of risk with a vegetarian diet for all types of cancer combined. The most remarkable benefits were for stomach cancer, where there was a 45% reduction in risk, lymphoma, with a 25% reduction in risk, and colorectal cancer, with a 21% reduction in risk.
Younger vegans had a 31% reduction in breast cancer; older vegans had a 26% reduction. Younger vegans had lower rates of prostate cancer. Younger seems to mean 65 or less.
The benefits of a vegetarian diet may be even greater than this study suggests for two reasons. The first is that nonvegetarian in this study meant people who eat meat one or more times a week. That means that a subset of the nonvegetarian group only ate meat once a week: many meat eaters eat meat much more often than that.
The second reason is that Adventists, including the nonvegetarian ones, are a relatively health conscious population that eats healthier and eats less meat. Nonvegetarian Adventists experience lower rates of cancer than the general population. The difference between vegetarians and nonvegetarians may have been greater in a more inclusive study population.
This study found lower risk of cancer overall and for several types of cancer for vegetarians. The clearest benefit was in stomach, colorectal, lymphoma, lymphoproliferative, prostate and breast cancers.
American Journal of Clinical Nutrition. August 2025;122(2):535-543.