A ketogenic diet, which is high in fat and low in carbohydrates, may increase the risk of developing small bowel cancer. Scientists from the Massachusetts Institute of Technology (MIT) came to this conclusion. The results of the study were published in the journal Nature.
Ketogenic diets, developed by doctors in the 1920s to treat epilepsy, have come to serve a different purpose in recent decades: weight loss, notes MIT News. The diet includes a high fat content, a minimal amount of carbohydrates, and a normal or reduced proportion of protein. With this ratio of nutrients, the body begins to use fatty acids rather than glucose as the main source of energy.
When fats are broken down, ketone bodies are formed – primarily beta-hydroxybutyrate (BHB) and acetoacetate. They are also produced during fasting or when following extremely low-calorie diets, when the body is forced to use up its own fat reserves.
During the experiment, scientists divided mice genetically predisposed to intestinal cancer into three groups. The animals received food corresponding to a ketogenic, regular or high-calorie diet.
The study found that mice on a ketogenic diet developed small intestinal tumors more often than animals in a control group on a normal diet. At the same time, they did not experience obesity, but neoplasms occurred with the same or even greater frequency than in mice fed high-calorie food that promotes weight gain.
Scientists have also found that ketone bodies themselves do not play a direct role in the development of tumors. Their growth turned out to be related to how intestinal cells process dietary fats. Fatty acid oxidation activates proteins like PPARs, which signal intestinal stem cells to multiply faster. The more cells divide, the higher the likelihood that some of them will become cancerous.
In certain circumstances, rapidly multiplying stem cells can be beneficial, such as when the intestinal lining is repairing itself after disease or injury. However, excessive proliferation, that is, cell division, increases the risk of them becoming cancerous.
What surprised scientists was that the ketogenic diet, which has been shown to promote the development of tumors in the small intestine, had the opposite effect on the colon.
A study published several years ago found that a ketogenic diet may reduce the risk of colon cancer. Then scientists suggested that this effect was associated with BHB. However, the authors of the new work came to the conclusion that the protective effect is also due not to ketone bodies, but to the peculiarities of the oxidation of fatty acids supplied with food.
“The deeper question is why the same diet produces opposite effects in two adjacent sections of the intestine. This is what we are going to find out in the next stage,” said study author Fantao Chi.
Scientists emphasize that the choice of dietary strategies, especially in people with a genetic predisposition, must be approached carefully.
“Ketogenic diets have different effects on different tissues, even within the gastrointestinal tract. The main takeaway is that we should be extremely careful in generalizing the possible effects of such diets, since what benefits one tissue may be harmful to another,” added author Omer Yilmaz.
