"Extreme" Dietary Manipulations
In recent years, interest in dietary manipulations in the treatment of cancer has increased, but the optimal strategies are not known. In preclinical studies, metabolic dietary therapies, such as calorie restriction, fasting, and ketogenic diets, have been shown to slow the growth of cancer, but few human clinical trials have been conducted. Calorie restriction has been shown in murine models of breast cancer to repress tumor growth in an additive manner during radiation therapy.
The ketogenic diet, which is very high in fat, involves eliminating nearly all carbohydrates from the diet, because cancer cells consume glucose derived from carbohydrates. Used for many decades to treat pediatric epilepsy, this very-low-carbohydrate diet strategy is aimed at starving cancer cells that are dependent on glucose, which has both direct and indirect effects on tumor proliferation.
Dixon comments that experimental aggressive diet interventions, such as the ketogenic diet, are not yet officially recommended in cancer guidelines. "Tumor biology is very complicated. What works for one tumor type is not necessarily going to be helpful for another. Moreover, the ketogenic diet is quite extreme. We need to make sure that patients will benefit, and not be harmed by it, before we recommend this diet."
Another intervention, which has shown promise in murine studies, is fasting before undergoing chemotherapy. Explains Dixon, "This involves the patient fasting for a day or two before chemotherapy, on the day of chemotherapy, and for a day or two afterwards. Fasting generally means drinking only water; no calories are ingested. The theory is that cancer is caused by uncontrolled growth and replication, so that by fasting and putting the body into a calorie-deficit state, the healthy cells become quiescent and go into 'housekeeping mode.' Only basic functions are carried out, but no growth or replication. This protects the healthy cells from the effects of chemotherapy, so patients will experience fewer or reduced side effects. The effect on the cancer cells is to sensitize them to chemotherapy, so that they are more susceptible to it."
However, Dixon emphasizes that "this is not yet a proven strategy, and it has mostly been patient-driven. It may be effective only for certain tumors; we don't know yet. But patients are reading about it online and want to try it. It's not being officially recommended, but some patients are doing it."
Does fasting work? Anecdotally, patients are reporting fewer side effects, such as mouth sores, diarrhea, and skin issues, says Dixon. An obvious question, however, is whether fasting is safe in patients who are at high risk for weight loss and cachexia. "We need to figure out how to do it safely," agrees Dixon. "In tumor types where it is unlikely that the patient will lose a lot of weight, we wouldn't be as concerned about short-term fasting. Most patients with such cancers as breast and prostate aren't losing a lot of weight doing it. And even if fasting does turn out to be safe, it will be important for patients to load up on fluids and keep the kidneys functioning. We need clinical trials -- in the next few years, we will have more data to sort out who will benefit and who shouldn't do it."
Medscape Oncology © 2013 WebMD, LLC
Cite this: Extreme Nutrition: Can It Beat Cancer? - Medscape - Nov 20, 2013.