Massachusetts Institute of Technology (MIT) researchers have found that a ketogenic diet produced opposite effects on cancer risk in different parts of the digestive tract in mice. The study, published in Nature, revealed that a high-fat, low-carbohydrate ketogenic diet accelerated tumor growth in the small intestine of mice predisposed to cancer, while simultaneously suppressing tumor formation in the colon. This finding challenges previously generalized views on the diet's anti-cancer properties.

This nuanced understanding of how ketogenic diets impact gastrointestinal health is important for individuals considering such diets, as it suggests that effects can vary significantly depending on the specific organ within the digestive system. The research indicates that what might be beneficial for one tissue could be detrimental for another, urging caution against broad generalizations about the diet's health impacts.

What the records show

The study, published in Nature on July 15, 2026, details experimental results from mice genetically predisposed to developing intestinal tumors. Researchers fed these mice one of three diets: a ketogenic diet, a standard control diet, or a high-fat, high-calorie diet designed to induce obesity. The unexpected results showed that the ketogenic diet increased small-intestinal stem cell activity and accelerated tumorigenesis in the small intestine. The increased risk was attributed to the way intestinal stem cells processed the diet's high levels of fat, rather than the production of ketone bodies, which are a hallmark of ketogenic diets. This fat-burning activity caused cells to multiply more rapidly, potentially increasing the chance of cancerous changes. Conversely, the same ketogenic diet reduced tumor formation in the colon. The study specifies that these are findings from a mouse study and not a clinical study on humans. Previous research, including a Nature study from 2022, had reported that ketogenic diets reduced colon tumor formation.

The timeline

Research regarding the ketogenic diet's impact on cancer has been ongoing. A previous Nature study in 2022 indicated that the diet could reduce colon tumor formation. The new findings, published in Nature on July 15, 2026, specifically detail the differential effects on the small intestine and colon. The study's findings became public through various reports in the following months, including articles on July 16, 2026, July 21, 2026, and October 5, 2026.

What changed and for whom

This research introduces a critical nuance to the understanding of ketogenic diets, challenging previously generalized views on their anti-cancer properties. While some research indicated potential protection against colon cancer, the new findings suggest an increased risk for cancer in the small intestine. This means that the impact of a ketogenic diet is not uniform across the digestive system, and its effects are tissue-specific. For patients with conditions like familial adenomatous polyposis (FAP), who frequently develop intestinal polyps, understanding these nuanced impacts is particularly relevant.

What the researchers have said publicly

Omer Yilmaz, director of the MIT Stem Cell Initiative, associate professor of biology at MIT, and a member of MIT's Koch Institute for Integrative Cancer Research, is the senior author of the study. Yilmaz stated, "I think the message here is that we need to be very careful in generalizing the effects that these diets can have, because what might be beneficial for one tissue may be detrimental for another tissue". He emphasized that "Ketogenic diets have distinct effects on different tissues even within the gastrointestinal tract". MIT postdoctoral researchers Jessica Shay and Fangtao Chi are lead authors of the paper.

What we could not confirm

We could not confirm if there are ongoing human clinical trials to validate these findings from mouse models. We also could not confirm the specific dietary recommendations or changes that might arise from these findings for human ketogenic diet practitioners.