The Telegraph published information on a study by the University of South Carolina that observed that fasting for as little as 3 days can have an regenerative effect on the immune system in people of all age groups.

Researchers found fasting activates the stem cells, causing an increase in white blood cell production.

White blood cells are the immune cells responsible for fighting infection. Fasting could potentially of benefit to people suffering with a suppressed or stressed immune system, e.g., people suffering cancer or the elderly .

According to the research, fasting has the ability to throw the regenerative switch, as the stem cells create  new white blood cells, which enhances the regeneration the immune system.

Valter Longo, the corresponding author of the study, says “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.”
“With a system heavily damaged by chemotherapy or aging, fasting cycles generate, literally, a new immune system,” he added.

For those interested in learning more about fastening, The Miracle of Fasting by Paul Bragg is an excellent place to start.