Researchers in the US have discovered that a high-fat, low-carbohydrate diet, known as the ketogenic diet, may be linked to small intestine cancer in mice.  

Besides helping people lose weight by forcing the body to burn fat for energy, previous research suggested that the keto diet can protect against colon cancer in the large intestine. This effect has been associated with a type of molecules, called ketone bodies, that are produced by the breakdown of fat. 

Researchers at the Massachusetts Institute of Technology wanted to understand if it had the same effect on the small intestine. By feeding mice genetically predisposed to develop intestinal cancer a control diet, ketogenic diet or a diet that leads to obesity, they found that mice on the ketogenic diet, despite not becoming obese, developed as many tumours as, or even more than, mice on the obesity diet. 

By genetically manipulating the fat breakdown responsible for producing ketone bodies in mice, the team discovered that these molecules are not involved in the formation or prevention of tumours. In the small intestine, they found that tumour formation was due to an increase in cell proliferation directly driven by how cells burned fat, thereby increasing the risk of cancer. 

"I think the message here is that we need to be very careful in generalising the effects that these diets can have, because what might be beneficial for one tissue may be detrimental for another tissue,” said Omer Yilmaz, researcher at MIT and leader of the study published in Nature. Future research will focus on understanding these opposite effects in the small and the large intestine.  

The findings also have a practical implication for the commercialisation of ketone supplements, since these molecules are seen as innocuous rather than drivers of the diet effects.