A study from the laboratory of Omer Yilmaz at MIT, with contributions from the Shalek and Vander Heiden groups, has found that ketogenic diets can promote tumour growth in the small intestine. Published in Nature, the work fed mice genetically predisposed to intestinal cancer one of three regimes: a ketogenic diet, a control diet, or a high-fat, high-calorie obesogenic diet, then compared tumour outcomes across the gut.
Mice on the ketogenic diet developed small-intestine tumours more often than controls, at rates similar to or higher than those on the obesogenic diet, despite never becoming obese. Strikingly, ketone bodies such as beta-hydroxybutyrate were not the culprit. Instead, the driver was intestinal cells burning dietary fat through fatty acid oxidation, which activates PPAR proteins and pushes stem cells to proliferate. The same diet suppressed tumours in the colon, an effect traced to lipids rather than ketones.
The findings arrive as ketogenic eating grows in popularity and as small-intestinal tumours become more common, and they suggest particular caution for people with familial adenomatous polyposis, who carry the same genetic vulnerability modelled in the mice. The authors note that ketone supplements are unlikely to reproduce the effect, since the mechanism runs through fat metabolism in the gut lining rather than ketosis itself.