A vegetarian diet does not protect against breast cancer

The largest study ever conducted on diet and cancer, involving no fewer than 1.8 million participants who detailed their dietary habits through questionnaires, concludes that vegetarians are less likely to develop five types of cancer, including breast cancer*. The researchers investigated links between dietary habits and 17 types of cancer. For five of them, they found a dietary effect. According to them, a vegetarian diet may protect against pancreatic cancer, prostate cancer, kidney cancer, multiple myeloma (a form of blood cancer), and breast cancer. They found the greatest effect for multiple myeloma and the smallest effect for breast cancer. Diet has barely any impact on the risk of breast cancer, as we know from other research. There is therefore another explanation for the small beneficial effect found in this study. Vegetarians are more likely to be people who are more health-conscious compared to the general population. For example, it is known that, on average, they exercise more, consume alcohol more sparingly, and smoke little or not at all. Sufficient physical activity and a healthy body weight are two factors that do protect against breast cancer. This explains why the vegetarians in this study developed breast cancer less frequently. Diet has an indirect effect. Eating a small piece of meat every now and then has no impact whatsoever on your risk of breast cancer. A healthy diet, with or without meat, is good for your overall health.

*Dunneram Y, Lee JY, Watling CZ, et al. Vegetarian diets and cancer risk: a pooled analysis of 1.8 million women and men in nine prospective studies across three continents. Br J Cancer 2026. doi: 10.1038/s41416-025-03327-4.

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