From Medscape, January 16, 2025

When it comes to naming the dietary patterns offering the most protection against cancer, plant-based diets emerge as the winner for reducing the risk for several cancers sensitive to lifestyle factors.

Though most research into dietary patterns over the past few decades has compared the Mediterranean diet with the Western diet, meta-analyses in the past 5 years have brought more attention to the benefits of plant-based diets. One of the leading hypotheses for the association between plant-based diets and reduced risk for certain cancers is how eating diverse plants affects the microbiome.

Most recently, for example, 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. That finding suggests eating a diet emphasizing plants may be more helpful for preventing cancer than cutting out meat.

Decades ago, the idea that changing lifestyle behaviors could have an impact on cancer risk was so radical that many dismissed it as “false hope” sold by “snake oil salesmen,” according to Nigel Brockton, PhD, the vice president of research at the American Institute for Cancer Research (AICR). Today, it’s far better understood that lifestyle factors play a major role in many different cancers, but researchers are still working to disentangle precisely how. Nowhere is that more complex than with diet, suggested experts.

“Particularly over the last 10 years, there’s been a push in the research for [investigating] dietary patterns rather than individual foods or macronutrients,” Brockton said. The problem is, “if you just tell someone to eat a healthy diet, that means different things to many different people.” But as the evidence accumulates, it increasingly points to one over-arching theme: More plants, less cancer.

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