Mardi Gras is just around the corner. Lent will begin, and many Christians will adjust their normal diet and give up certain foods or practice fasting. Religions and philosophies that practice fasting include Buddhism, Christianity, Islam, Judaism, Taoism, Jainism, and Hinduism. Voluntary fasting has been performed for many centuries and purposes, such as religious, ethical, and cosmetic. Hippocrates was probably one of the first advocates of fasting for medical purposes (he recommended fasting during sickness).
So what does fasting have to do with cancer?
Well, we know that cancer thrives on glucose. So what if someone with cancer is deprived of sugar? Some evidence shows that a ketogenic diet, which starves the body of carbohydrates rather than all calories, may increase the efficacy of some cancer treatments. But let’s take it beyond a ketogenic diet and explore the benefits of short-term fasting to battle cancer.
First, let’s make it clear that fasting is safe. The first clinical study of medical fasting for the treatment of obesity was performed in 1915. The authors reported that short periods of four to six days of fasting was a safe and effective method for reducing body weight in obese humans.
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. It sounds counterintuitive to practice fasting during cancer treatment, but a growing body of research suggests that fasting decreases the toxicity of cancer treatments and may increase their efficacy too. Extensive animal preclinical evidence suggests that short-term fasting can protect healthy cells against the perils of a wide variety of stressors, including chemotherapy. More importantly, the studies showed that fasting seemed to make cancer cells more vulnerable to chemotherapy.
Essentially, fasting causes a switch in healthy cells from a proliferative state towards a maintenance and repair state. Malignant cells, in contrast, fail to adapt to nutrient-scarce conditions. Instead, fasting deprives cancer cells of nutrients, growth, and other factors, which renders them more sensitive to cancer therapy and increases cell death.
A landmark study randomizing 131 patients with HER2-negative stage II/III breast cancer showed the effects of a fasting diet on the toxicity and efficacy of chemotherapy. The results suggested that the fasting significantly reinforced the effects of neoadjuvant chemotherapy on the radiological and pathological tumor response in patients with HER2 negative early breast cancer. It also showed a complete response occurred approximately three times more often in the fasting group compared to the control group.
Several other trials in humans, all of the following small patient populations for short periods of time, have also found that fasting reduced treatment-related toxicities such as fatigue. 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. researchers found evidence that fasting reduced bone marrow toxicity and reduced chemotherapy-induced DNA damage in some healthy blood cells.
In a case series from the University of Southern California (USC), 10 patients with different malignancies fasted in combination with docetaxel, carboplatin, paclitaxel, and/or gemcitabine. Besides hunger and dizziness, fasting had no significant side effects. The authors reported a decrease in chemotherapy-induced side effects, including fatigue, weakness, vomiting, and diarrhea, when chemotherapy was combined with short-term fasting compared to chemotherapy alone.
To determine the safety of fasting for cancer patients, researchers from USC conducted a dose-escalating phase I study, wherein 20 patients with distinct malignancies were treated with platinum-based chemotherapy combined with a 24, 48, or 72-hour fast to identify the optimal fasting duration. The authors reported that a 72-hour fast was associated with normal lymphocyte counts and maintenance of a normal lineage balance in white blood counts. Researchers concluded that a 72-hour fast (48 hours before chemo and 24 hours after chemo) was safe and feasible in human cancer patients receiving platinum combination chemotherapy. Preliminary evidence from correlative studies supported the hypothesis that fasting may confer some protection to host tissues against chemotherapy damage to normal tissues.
Finally, Researchers from Berlin, Germany did a randomized cross-over trial evaluating the effect of short-term fasting on quality of life in breast cancer and ovarian cancer patients treated with chemotherapy. Patients were randomized to fast (36 hours before chemo, 24 hours after) or to eat a normal Mediterranean diet for the first three cycles of chemotherapy. The fasting was safe and feasible. The authors concluded that short-term fasting led to a better tolerance to chemotherapy with less compromised quality of life and reduced fatigue within the eight days after chemotherapy. Moreover, 31 patients declared that they would fast again during chemotherapy, while only three patients declared that they would not.
These early clinical studies lack enough power to draw definite conclusions. However, the first results suggest that short-term fasting is safe while reducing the toxicity of chemotherapy. Large scale randomized studies are required to get more insight into the benefits of short-term fasting in cancer patients.
Positive results could change standards of care for all those tumor types within the next couple of years.
Fasting therapy was observed to be generally safe and well-tolerated. Only mild side effects were reported, including headaches, dizziness, nausea, dyspepsia, and fatigue. However, in rare cases fasting for periods longer than two weeks was fatal.
In conclusion, abundant and convincing evidence shows that short-term fasting can decrease toxicity and simultaneously increase the efficacy of a wide variety of chemotherapeutic agents. It appears safe as an adjunct to chemotherapy in humans, and it may reduce side effects and DNA damage in healthy cells in response to chemotherapy. However, more research is needed to firmly establish clinical efficacy and safety.
Dr. Paul Zhang at the Institute of Integrative BioOncology in Houston provides evidence-based treatments for a wide range of cancers. Call today for more information.
