Keto diet raises small-intestine tumors, cuts colon tumors

A new study from the Massachusetts Institute of Technology has found that a ketogenic diet can have opposite effects on cancer risk in different parts of the digestive tract, accelerating tumor growth in the small intestine while suppressing it in the colon. The research, published July 15 in Nature, challenges a leading theory that the diet’s effects on cancer are driven by ketone bodies, pointing instead to the metabolism of dietary fat as the key mechanism.

Researchers at MIT’s Koch Institute for Integrative Cancer Research fed mice genetically predisposed to intestinal cancer either a ketogenic diet, a standard control diet, or a high fat, high calorie diet that typically causes obesity. Mice on the ketogenic diet developed significantly more tumors in the small intestine than those on the control diet, with tumor rates comparable to or even higher than those in the obese mice, despite the ketogenic group remaining lean. At the same time, the same diet suppressed colon tumor development, confirming earlier findings.

The team expected that ketone bodies, particularly beta hydroxybutyrate, would be responsible for these effects. Instead, experiments revealed that the increased...