A ketogenic diet—high in fat and very low in carbohydrates—has been linked to weight loss and even protection against colon cancer. But new research from MIT suggests the same diet may have the opposite effect in the small intestine. In mice, the diet increased the likelihood of tumors forming in that part of the gut, even as it suppressed colon tumors.
The MIT team, led by Omer Yilmaz, found that the tumor growth was tied to how intestinal cells burn dietary fat for energy, a process called fatty acid oxidation. That pathway activates proteins that make stem cells multiply more rapidly. More active stem cells can aid repair after injury, but they also create more opportunities for cancer to develop.
Interestingly, the study indicates that ketone bodies—by-products of the diet often credited with health benefits—are not involved. Yilmaz calls them "metabolic bystanders," suggesting commercial ketone supplements probably do little to help or harm. The researchers now want to understand why one diet can have opposite effects in two adjacent parts of the gut. As Yilmaz puts it, "we need to be very careful in generalizing the effects that these diets can have."