Fasting rejuvenates the immune system

VALLEY — The concept of therapeutic fasting is not new, yet only recently have its profound immune boosting benefits been discovered.

Fasting works because the body has the capacity to heal when the obstacles to healing are removed. I have been using fasting as a healing strategy throughout my career as a physician. In my 1995 book, Fasting and Eating For Health, I described my observations of health improvements due to fasting. Fasting promotes accelerated healing and is a valuable treatment for a variety of medical conditions. In fact, I and my colleagues published a series of case reports that showed remission of autoimmune diseases following supervised fasting.  Reviews of studies on fasting supported those findings, concluding that fasting (followed by a vegetarian or vegan diet) produces improvements in symptoms for patients with autoimmune diseases.

Fasting is a powerful healing modality that has been used for many years, but only now are research studies uncovering specifically how fasting works on a cellular level. These new studies are generating more interest in fasting. Fasting, after glycogen stores (stored glucose) are depleted during the first 24-48 hours, sets off complex biochemical pathways in the body that aim to conserve energy while adequately fueling vital organs, and these energy conserving mechanisms may have beneficial side effects. A recent study suggests that fasting promotes the regenerative capacity of the immune system that could benefit cancer patients undergoing chemotherapy, and healthy individuals too.

Previous research had suggested that fasting could protect mice against toxicity from chemotherapy (without compromising the effectiveness of the chemotherapy). Also, in a series of 10 case reports of patients who had voluntarily fasted alongside some of their chemotherapy treatments, all of the patients experienced fewer and less severe side effects during fasting cycles compared to non-fasting cycles of chemotherapy.

In an extensive series of experiments, a group of scientists showed that fasting reduced chemotherapy-induced mortality in mice. After 4-5 cycles of fasting accompanying chemotherapy, the white blood cell count of the fasting group returned to normal, but the control group’s remained diminished by the chemotherapy. Next, they looked at fasting without chemotherapy, and found similar results. Fasting was able to provoke regeneration of the immune cells in healthy mice, and also returned the stem cell profile of aging mice to that of younger mice. The scientists were surprised at these dramatic results, which suggested that fasting signals the immune system to get rid of old or damaged cells and rebuild itself with new cells.

A clinical trial assigned patients undergoing chemotherapy to either 24 or 72 hour fasts prior to each chemotherapy cycle. Preliminary results were similar to what was seen in mice; the 72 hour fasting group saw an improvement in immune cell count and a shift toward the ‘younger’ cellular profile.

What could this mean for patients with cancer? The toxicity and side effects associated with chemotherapy are a major limitation for treatment of cancer.  An important research goal is to identify an adjunct treatment that could ameliorate those side effects without compromising the effectiveness of the chemotherapy. Research suggests that fasting could achieve these goals and even make chemotherapy more effective.  In other words, fasting is thought to protect normal cells while making cancerous cells vulnerable.

Depriving normal, healthy cells of energy-yielding nutrients signals them to set aside growth and go into a mode of energy conservation, protection, maintenance, and repair. It increases the capacity of these cells for stress resistance. Since cancerous cells have mutations that hyperactivate growth pathways, causing uncontrolled proliferation, they are unable to go into the protective stress-resistance mode like healthy cells. This is called “differential stress resistance.” Fasting appears to induce stress resistance in normal cells but vulnerability in cancerous cells.

After the early series of 10 case reports noted a low rate of side effects in patients that had fasted prior to chemotherapy, additional studies in human patients were undertaken. The studies were small, but the results are positive. In one study, patients who fasted for 48 or 72 hours showed reduced chemotherapy-related side effects (including fatigue and nausea) and DNA damage in white blood cells compared to those who completed a shorter fast of 24 hours.  A randomized controlled trial in women with breast cancer also showed evidence of attenuated DNA damage due to chemotherapy in the fasting group compared to the non-fasting group over the course of multiple chemotherapy cycles. Future studies are needed to determine whether fasting strengthens patients’ response to chemotherapy, and also to determine the optimal fasting length for reducing side effects. Potentially this research could lead to a widespread use of fasting as an adjunct treatment alongside chemotherapy.

My book, Fasting and Eating for Health, is still a must read for the health enthusiast, though 20 years ago we did not know about fasting’s potential to help rejuvenate the immune system and sensitize cancerous cells. 

Dr. Fuhrman is a #1 New York Times best-selling author and a board certified family physician specializing in lifestyle and nutritional medicine. The Eat To Live Cookbook offers over 200 unique disease-fighting delicious recipes and his newest book, The End of Heart Disease, offers a detailed plan to prevent and reverse heart disease using a nutrient-dense, plant-rich eating style. Visit his informative website at Submit your questions and comments about this column directly to [email protected].