Fasting Generates a New Immune System


A new study in the journal Cell Stem Cell shows that cycles of prolonged fasting prompts the human immune system to rejuvenate hematopoietic stem cells from dormancy to a state of self-renewal. Hematopoietic stem cells, which reside in bone marrow, are those from which all other blood cells are derived. The findings represent the first academic confirmation of a natural action prompting stem regeneration of an organ or system.

One of the authors of the study, Valter Longo, a professor at the University of Southern California (USC) Davis School of Gerontology, labeled the effect “remarkable.” When the human body is starved, he said, it tries to conserve energy. One of the ways it does this is to “recycle” immune cells, including those which may be damaged.

Humans in the six-month clinical trials fasted regularly for between two and four days over a six-month period. It has been known that fasting forces the body to use glucose, fat and ketones it has held in storage. Now, with the new study, it is also known that three-day fasts break down a meaningful portion of white blood cells. Longo compares the effect to ridding an airplane of extra baggage.

Not eating for long periods lowered white blood cell counts significantly. Simultaneously, it is as if “a regenerative switch” was flipped for hematopoietic stem cells, thus providing the first, important step in the generation of blood and the regeneration of immune systems. Professor Longo says that once this “OK” is issued, stem cells proliferate, and rebuilding of the entire, critically-important immune system commences.

The new discovery will likely be helpful to cancer patients who are doing chemotherapy treatments and their inevitably damaged immune systems. It could also be helpful for elderly people, whose immune systems are less effective and for whom the fighting off of common diseases is more difficult.

Longo’s team noticed that, in both humans and animals, white blood cell counts decreased when associated with fasting. Each cycle of fasting depletes white blood cells in the body, thus triggering changes that begin the stem cell-based regeneration of new immune system cells. Toxicity was also seen as being protected against with fasting.

Tanya Dorff, a co-author of the study and an assistant professor at the USC Norris Comprehensive Cancer Center and Hospital, noted that chemotherapy causes significant incidental damage to the human immune system, and the study suggests that fasting may allay some of the damage caused by the chemotherapy. More studies are needed, she cautioned, and suggested that any such attempts to fast should only happen with a physician’s supervision. Cycles of fasting can literally generate a new immune system, she said.

Some experts are skeptical of the research. “Improbable” is the opinion of Dr. Graham Rook from University College London (UCL). Although his UCL colleague, Chris Mason, concedes that fasting could be helpful, he believes “the most sensible way forward” would be to fake the body into believing it is fasting, not by starving it of food, but with drugs. “I am not sure fasting is the best idea. People are better off eating on a regular basis,” he said. Dr. Long counters, stating that no evidence exists that fasting is dangerous to chemotherapy patients while, at the same time, firm evidence now exists that it can be beneficial.

By Gregory Baskin

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