Fasting may often be associated with spiritual meditation and discipline but abstaining from food for two to four days at a time apparently has benefits to the physical wellbeing as well. Researchers find evidence that suggest prolonged fasting is beneficial to the body as it helps fight the negative effects of aging to the immune system.

The white blood cells that protect the body from diseases and harmful invaders deteriorate as we age and this weakens the body's immune system making it hard for the elderly to fight off infection and putting them vulnerable to even to common diseases.

For the new study "Prolonged Fasting Reduces IGF-1/PKA to Promote Hematopoietic-Stem-Cell-Based Regeneration and Reverse Immunosuppression" which was published in the journal Cell Stem Cell on June 5, researchers from the University of Southern California (USC) discovered that prolonged fasting can help reverse this negative effect of aging as it induces renewal of the body's immune system.

The researchers found that fasting for two to four days can prompt the body to conserve as much energy as possible and as a result causes it use up stored fat and sugar as well as destroy old, weak and damaged immune cells in the body. While fasting initially lowers the body's white blood cell count, the body begins producing white blood cells in greater number once feeding is resumed and in the process regenerates the body's immune system.

"We discovered that this effect, which may have evolved to reduce energy expenditure during periods of starvation, is able to switch stem cells to a mode able to not only regenerate immune cells and reverse the immunosuppression caused by chemotherapy, but also rejuvenate the immune system of old mice," said study researcher Valter Longo, from the USC's Davis School of Gerontology.

Longo and his colleagues also found that fasting reduces the enzyme PKA, which Longo explained needs to shut down to induce self-renewal in stem cells and boost their pluripotency, or the ability of the cells to develop into different types of cells. The researchers likewise found that long periods of fasting also reduces the levels of a growth hormone known as IGF-1 which is associated with aging and cancer risks.

"It gives the OK for stem cells to go ahead and begin proliferating and rebuild the entire system," Longo said. "Now, if you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system."

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