From a new study out of USC, it was learned that in both mice and humans, fasting caused stem cell regeneration of the immune system, after damage was done by chemotherapy.  Fasting was said to have "flipped a regenerative switch" activating the response of hemopoietic stem cells in the bone marrow which are responsible for building blood and immune cells.

“We are investigating the possibility that these effects are applicable to many different systems and organs, not just the immune system,” said Longo, whose lab is in the process of conducting further research on controlled dietary interventions and stem cell regeneration in both animal and human studies.

“We could not predict that prolonged fasting would have such a remarkable effect in promoting stem cell-based regeneration of the hematopoietic system,” said corresponding author Valter Longo, Edna M. Jones Professor of Gerontology and the Biological Sciences at the USC Davis School of Gerontology and director of the USC Longevity Institute.

The process involved the reduction in an enzyme known as PKA which is believed to suppress stem cell regeneration. “PKA is the key gene that needs to shut down in order for these stem cells to switch into regenerative mode. It gives the OK for stem cells to go ahead and begin proliferating and rebuild the entire system,” explained Longo, noting the potential of clinical applications that mimic the effects of prolonged fasting to rejuvenate the immune system. “And the good news 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 longest fast involved was 4 days, and it resulted in the removal of old, damaged immune cells and their replacement with new ones.

I have been involved in conducting fasts for people most of my adult life, and I have seen fasts much longer than 4 days. The longest fast I have ever done is 28 days. That's water-only for 28 days. And the longest fast I have ever supervised is 40 days. However, we know beyond doubt that there have been fasts much longer than that- longer than 100 days. 

To many people, not eating for an extended period may seem drastic, but in practice, it's not as hard as it seems. For one thing, hunger disappears after a day or two. The ketosis of fasting, in which the body switches from burning glucose to burning fat, takes away the appetite. Most people feel quite indifferent to food while they are fasting. In fact, the biggest complaint we hear from fasters is not that they are hungry but that they are bored. And that's why we keep a lot of books and movies around to help them pass the time. Freeing the body from having to process food from scratch, saves the body a tremendous amount of energy and work. And, the process of living on one's reserves, forces the kind of cleaning-out of old damaged cells that we are looking for. The breakdown of tissues during fasting (in search of food) is a rigidly controlled process, and it results in discarding the bad and hoarding the good. You can compare it to peeling back the layers of an onion to get to younger, fresher tissue.

 I am proud to say that I am one of the most experienced fasting practitioners in the world.  And, I know that under the right environment and with the right conditions, fasting is one of the most healing and regenerative things that a person can do, as it aids and benefits a broad array of health issues. It would be great if the medical world became more aware of fasting and its potential to enhance human lives.