Early Evidence Shows That Fasting and Ketogenic Diet Help to Fight Cancer
Cancer loves glucose, which is why fasting, restricting calorie consumption or following the ketogenic diet may make chemotherapy and some other cancer treatments more effective and easier to tolerate, early evidence shows.
It’s hard to imagine a more counterintuitive cancer treatment than fasting. Why deprive the body of vital nutrients when it would seem to need them most? However, a growing body of research suggests that fasting decreases the toxicity of cancer treatments and may increase their efficacy as well. Some evidence also shows that a ketogenic diet, which deprives the body of carbohydrates rather than deprivation of total calories, may increase the efficacy of some cancer treatments. Additionally, there is even some thought that intermittent fasting and ketogenic diets may help prevent cancer, although evidence for this is currently limited.
Prevention may be the answer after all. Healthy cells and tumor cells respond differently to fasting. Healthy cells shut down their growth-promoting pathways shortly after the food stops coming in and focus on cell repair. Cancer cells, on the other hand, rarely slow their unrestrained growth enough to engage in this self-protective behavior. Fasting thus increases the ability of healthy cells to withstand stressors such as chemotherapy or radiotherapy, but it leaves cancer cells, which suddenly have less nutritional support to sustain their rapid growth, unusually weak and vulnerable. Fasting also depletes stored carbohydrates. Normal cells can adapt to this by running mostly on two fat-derived energy sources, fatty acids and ketones. Yet cancer cells are far more reliant on sugars, starches and the insulin that drives them into cells.
The first clinical trial of short-term fasting in humans, which was published in 2009, reported results in 10 patients with various types of cancer. It found that fasting reduced chemotherapy-related toxicities (i.e. fatigue, weakness and gastrointestinal side effects) in the six patients who fasted 48 to 140 hours before and five to 56 hours after some (but not all) of their chemotherapy sessions.
Several other trials in humans, all of them following small patient populations for short periods of time, have also found that fasting reduced treatment-related toxicities such as fatigue or DNA damage in healthy cells. For example, one Dutch trial assigned six patients with breast cancer to follow normal dietary guidelines and seven others to fast 24 hours before and after chemotherapy. Nonhematological toxicity did not differ between the two groups, but the researchers found evidence that fasting reduced bone marrow toxicity and reduced chemotherapy-induced DNA damage in some healthy blood cells.
Data from several of these small trials also suggest that fasting increases treatment efficacy, but none of them were large enough (or lasted long enough) to prove that fasting extended patients’ survival. There is even less evidence to support the use of fasting or the ketogenic diet in combination with immunotherapy treatments, although that remains a tantalizing possibility.
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