A ketogenic diet increased small-intestinal tumors in cancer-prone mice and reduced tumors in the colon

What the research found

Study (mice genetically predisposed to intestinal cancer). ScienceDaily carried the MIT account on 5 October 2026. Jessica Shay, Fangtao Chi, Omer Yilmaz, and colleagues report in Nature (2026; 656(8127):474; doi 10.1038/s41586-026-10779-y). Mice on a ketogenic diet developed small-intestinal tumors more often than mice on a control diet, at rates similar to or higher than mice on a high-fat, high-calorie diet, without the keto group becoming obese. The increase was traced to intestinal stem cells burning dietary fat, which switched on PPAR proteins and made the stem cells divide faster, not to ketone bodies such as beta-hydroxybutyrate. In the colon, the same diet suppressed tumors, and again ketones were not the driver. The authors say ketone drinks would not be expected to reproduce either effect. The release does not give animal counts. These are mouse findings in a cancer-prone strain, not a human diet trial. Educational notes. This is not a reason to start or stop a ketogenic diet.

Evidence level: Animal study. Results in animals or cells often don't carry over to people.

Read the original at Massachusetts Institute of Technology / Nature