A ketogenic diet has become one of the world’s most popular eating plans. It is very high in fat, very low in carbohydrates, and contains moderate amounts of protein.
By cutting carbohydrates, the body switches from using sugar as its main fuel to burning fat instead. This process produces compounds called ketones, which provide energy when glucose is limited.
Many people use ketogenic diets to lose weight or improve blood sugar control, and researchers have also explored whether they might help prevent some diseases, including cancer.
However, a new study from the Massachusetts Institute of Technology (MIT) shows that the effects of this diet may not be the same throughout the body. The research, published in Nature, found that while a ketogenic diet may reduce colon cancer, it could increase the risk of cancer in the small intestine.
The scientists focused on two neighboring parts of the digestive system: the colon and the small intestine. Although they are connected, they perform different jobs and contain different types of cells. Earlier research suggested that ketogenic diets could slow the growth of colon cancer, leading many researchers to wonder whether the same protection would occur in the small intestine.
To investigate, the MIT team studied mice genetically prone to developing intestinal cancer. Some mice received a ketogenic diet, while others ate a standard diet or a calorie-rich, high-fat diet that often causes obesity.
Surprisingly, mice eating the ketogenic diet developed significantly more tumors in the small intestine than mice eating the normal diet. Even though the ketogenic mice did not become obese, their tumor rates were similar to, or even higher than, those of mice fed the unhealthy high-calorie diet.
The researchers expected ketones to be responsible for the changes, but the experiments showed something different. Instead, the increased cancer risk was caused by the way intestinal stem cells burned large amounts of dietary fat. This process, known as fatty acid oxidation, activated proteins called PPARs that encouraged stem cells to divide more often.
Stem cells are essential because they repair the lining of the intestine after injury. However, when they become too active, they also have more opportunities to accumulate harmful changes that can eventually develop into cancer.
Interestingly, the same ketogenic diet had the opposite effect in the colon. It continued to reduce colon tumor growth, confirming earlier findings.
Even more surprising, the researchers discovered that ketones themselves were not responsible for either the harmful effects in the small intestine or the protective effects in the colon. Fat metabolism, rather than ketone production, appeared to be driving both outcomes.
The findings are important because ketogenic diets have become increasingly popular for weight loss and other health goals. They also suggest that commercial ketone drinks and supplements are unlikely to provide the same cancer-related effects because the study indicates that dietary fat metabolism, not ketones, is the key factor.
The study was performed mainly in mice, so it does not prove that ketogenic diets increase small-intestinal cancer risk in people. Human studies will be needed to determine whether the same biological processes occur. Nevertheless, the research provides an important reminder that nutrition is complex and that the same diet can affect different organs in very different ways.
Overall, this study challenges the idea that ketogenic diets have a single effect on cancer. Its strength lies in uncovering a specific biological mechanism explaining why different tissues respond differently.
However, because the work relied on animal models, caution is needed before applying the findings directly to human diets. Future clinical research will be essential to determine which people may benefit from ketogenic diets and which individuals might face greater risks.
If you care about cancer, please read studies that a low-carb diet could increase overall cancer risk, and vitamin D supplements could strongly reduce cancer death.
For more health information, please see recent studies about how drinking milk affects the risks of heart disease and cancer and results showing higher intake of dairy foods linked to higher prostate cancer risk.
Source: Massachusetts Institute of Technology (MIT).
