People who ate a primarily vegetarian diet had a reduced risk for overall cancer and for several specific cancers compared with people who were nonvegetarian, according to a study.

The new findings, published in The American Journal of Clinical Nutrition, lend more credence to the existing evidence base suggesting that a heavily plant-based diet may reduce cancer risk.

A 2012 meta-analysis of seven studies found that vegetarians had an 18% lower risk for cancer than nonvegetarians. Similarly, a 2017 meta-analysis of 10 prospective cohort studies revealed an 8% reduced risk for cancer among vegans and vegetarians compared with omnivores. Another meta-analysis of eight studies with 686,691 participants published in 2023 showed vegetarian diets lowered the risk for gastrointestinal cancers, specifically, by 23%, with greater benefits for men and Asian populations.

More recently, a study published on January 6 in Nature Microbiology compared the microbiomes of vegans, vegetarians, and omnivores across five cohorts totaling 21,561 individuals. Omnivores had more bacteria linked to increased risk for colon cancer, the researchers found, and microbes with favorable cardiometabolic markers were particularly plentiful in vegans’ microbiomes. But those healthy microbes in vegans also appeared in greater amounts in the microbiomes of omnivores who ate more plant-based foods.

In the new study, vegetarians had a 12% lower risk for any type of cancer than non-vegetarians (hazard ratio [HR], 0.88; P < .001) and an 18% lower risk for cancers that occur with medium frequency (HR, 0.82; P < .001). Cancers categorized as occurring with medium frequency included melanoma, lymphoma, myeloid leukemias, and endometrial, renal, urothelial, thyroid, ovarian, central nervous system, lung, rectal, pancreatic, primary liver, stomach, esophageal, mouth-pharyngeal-laryngeal, and lymphoid cancers.

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