MIT researchers studied mice genetically prone to intestinal cancer, feeding one group a regular diet, one a high-fat high-calorie diet and one a ketogenic diet.

According to MIT News, as reported by Yahoo Health and Blavity, keto-fed mice were more likely to develop small intestine tumors, with tumor rates matching or exceeding the high-calorie group — yet the mice did not become obese. Surprisingly, the same diet suppressed tumors in the colon.

The counterintuitive twist is that ketones were not the culprit.

The problem traced back to how intestinal stem cells burn dietary fat, switching on PPAR proteins that pushed stem cells to divide faster, creating more chances for cells to turn cancerous, senior author Omer Yilmaz, PhD, told MIT News.

Lead author Fangtao Chi, PhD, called the deeper question why the same diet has opposite consequences in two adjacent parts of the gut, per ScienceDaily.

Experts urge caution before turning a mouse study into a diet rule. Dietitian Danielle Smiley, RDN, who medically reviewed the Blavity piece, agreed the research raises questions worth investigating but noted the mice were genetically predisposed to intestinal tumors.

The MIT researchers specifically flagged familial adenomatous polyposis, an inherited condition raising duodenum cancer risk.

Beyond cancer questions, experts cited trade-offs including the "keto flu," low fiber intake causing constipation, elevated LDL cholesterol, and long-term risks of kidney stones, gout and bone mineral loss.

Smiley and Rachel Harvest, MS, RDN, both favor a Mediterranean-style or moderate-carbohydrate eating pattern adapted to personal preferences. The American Cancer Society recommends vegetables, whole fruits, whole grains, limited red and processed meats, and little or no alcohol to lower cancer risk.