Fasting's not as dumb as you thought

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Eating regimes that involve fasting, like the popular 5:2 diet, cop a lot of criticism. For many of us, dramatically cutting down on food intake, or not eating at all for periods of time, seems like an extreme and nutritionally dubious approach to eating – and several experts agree.

However, a new study suggests fasting can actually benefit the immune system by “flipping a regenerative switch”.

Scientists at the University of Southern California found fasting for 72 hours can regenerate the entire immune system, as it prompts the body to produce fresh new white blood cells.

Clinical tests revealed starving the body in prolonged cycles — no food for two to four days at a time over the course of six months — altered the signalling pathways for hematopoietic stem cells, which generate the blood and immune systems.

Study author Professor Valta Longo says fasting depletes the body’s supply of white blood cells, which in turn triggers stem cells to regenerate: “When you starve, the system tries to save energy, 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.”

This surprising discovery, which has been described as ‘remarkable’, could be good news for people whose immune systems are damaged (like cancer patients undertaking chemotherapy), deficient or weakened due to ageing. Interestingly, fasting had an additional benefit for chemo patients in that it appeared to relieve some of the harmful effects of the treatment.

These findings were published in the June 5 issue of Cell Stem Cell.