We hear an awful lot about fasting for the purposes of weight loss, but the practice may also have some serious benefits for cancer patients.
A couple of days of fasting may actually re-energize the immune system so that old cells are killed off and new cells are primed to grow. The practice has potentially huge implications for people who are undergoing chemotherapy, as well as for those who just want to improve the health of their immune systems.
“We could not predict that prolonged fasting would have such a remarkable effect,” said study author Valter Longo of the University of Southern California in a statement. He and his team have studied fasting in the past, and the new work builds on the old by looking at both mice and people in a phase I clinical trial.
Phase 1 clinical trials are the first stage of drug testing. They involve those drugs that have been tested extensively in the laboratory and on animals with encouraging results, but have not yet been given to humans. Patients in Phase 1 trials are sometimes the first to try new cancer drugs.
When the body goes into starvation mode, it reacts by ‘dumping’ what it doesn’t need — old white blood cells — it's like dumping cargo from an airplane to lighten it.
The USC team found that in humans, fasting for three days before having chemotherapy reduced the toxicity of the powerful drugs and also lowered white blood cell counts. In mice, fasting not only reduced white blood cell counts, it increased the number of hematopoietic stem cells, which are capable of becoming both immune system cells and red blood cells.
When in a fasting state, the body tries to conserve resources by killing off old, unnecessary immune cells, the team believes.
“When you starve, the system tries to save energy,” says Longo, “and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged. What we started noticing in both our human work and animal work is that the white blood cell count goes down with prolonged fasting. Then when you re-feed, the blood cells come back. So we started thinking, well, where does it come from?”
The team was able to illustrate the mechanisms behind the results in mice. They found fasting led to lowered levels of two key enzymes: One was PKA. Lower levels of PKA have been linked to increased lifespan and stem cell renewal. The other enzyme was IGF-1, which has been linked to cancer cell growth and aging. The reduction of both these enzymes can recharge the immune system.
Longo says that when the body goes into starvation mode, it reacts by “dumping” what it doesn’t need — old white blood cells — which he compares to dumping cargo from an airplane to lighten it.
“And the good news,” he says, “is that the body got rid of the parts of the system that might be damaged or old, the inefficient parts, during the fasting. Now, if you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system. ”
The results have some promising implications for people undergoing chemo, and perhaps those dealing with autoimmune illnesses. And it may help healthy people keep their immune systems in tip-top shape.
More research will be needed to understand all the effects of fasting, along with any adverse effects. So don’t try this at home just yet. But the researchers are continuing to look into the fasting effect, so we should know more in the not-too-distant future.
The research is published in Cell Stem Cell.