MIT Scientists Identify a Potential Cancer-Related Concern With the Keto Diet

A ketogenic diet may have contrasting effects on cancer development in different parts of the digestive tract, promoting small intestinal tumors while suppressing colon cancer in mice, according to a study published in Nature.

A ketogenic diet is high in fat and very low in carbohydrates, encouraging the body to burn fat for energy. Researchers investigated whether this metabolic shift could influence intestinal cancer development.

The study, conducted by researchers at the Massachusetts Institute of Technology (MIT), examined mice genetically predisposed to intestinal cancer. Animals receiving a ketogenic diet developed small intestinal tumors more frequently than those consuming a control diet.

Further experiments revealed that the effect was linked to fatty acid oxidation, the process through which cells break down fat for energy, rather than ketone bodies produced during fat metabolism.

Increased fatty acid oxidation activated proteins called peroxisome proliferator-activated receptors (PPARs), which stimulated intestinal stem cells to divide more rapidly. Although stem cell activity helps repair intestinal tissue, excessive cell division may increase opportunities for cancerous growth.

Interestingly, researchers observed the opposite effect in the colon, where the ketogenic diet suppressed tumor formation. This finding was consistent with earlier research suggesting that ketogenic diets may offer protection against colon cancer.

However, the new findings challenge the assumption that ketone bodies are directly responsible for this protective effect. Instead, researchers believe differences in how cells process dietary fat may explain the contrasting outcomes.

The findings also raise questions about the potential effects of ketogenic diets in people with inherited conditions that increase susceptibility to intestinal cancer, including familial adenomatous polyposis.

Researchers are now investigating why the same diet can produce opposing effects in neighbouring regions of the digestive tract. Until human evidence becomes available, these findings should not be interpreted as proof that ketogenic diets increase cancer risk in people.

REFERENCE: Jessica E. S. Shay, et al.; Ketogenic diet mediates intestinal tumorigenesis through lipids not ketones. Nature, 2026; 656 (8127): 474 DOI: 10.1038/s41586-026-10779-y