"A person's entire immune system can be
rejuvenated by fasting for as little as three days as it triggers the body to
start producing new white blood cells, a study suggests"
Photo: PEGAZ/Alamy |
Fasting for as little as
three days can regenerate the entire immune system, even in the elderly,
scientists have found in a breakthrough described as "remarkable".
Although fasting diets
have been criticised by nutritionists for being unhealthy, new research
suggests starving the body kick-starts stem cells into producing new white
blood cells, which fight off infection.
Scientists at the
University of Southern California say the discovery could be particularly
beneficial for people suffering from damaged immune systems, such as cancer
patients on chemotherapy.
It could also help the
elderly whose immune system becomes less effective as they age, making it
harder for them to fight off even common diseases.
The researchers say
fasting "flips a regenerative switch" which prompts stem cells to
create brand new white blood cells, essentially regenerating the entire immune
system.
"It gives the 'OK'
for stem cells to go ahead and begin proliferating and rebuild the entire
system," said Prof Valter Longo, Professor of Gerontology and the
Biological Sciences at the University of California.
"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 ageing, fasting cycles can generate,
literally, a new immune system."
Prolonged fasting forces the body to use stores of glucose and fat but
also breaks down a significant portion of white blood cells.
During each cycle of fasting, this depletion of white blood cells
induces changes that trigger stem cell-based regeneration of new immune system
cells.
In trials humans were asked to regularly fast for between two and four
days over a six-month period.
Scientists found that prolonged fasting also reduced the enzyme PKA,
which is linked to ageing and a hormone which increases cancer risk and tumour
growth.
"We could not predict that prolonged fasting would have such a
remarkable effect in promoting stem cell-based regeneration of the
hematopoietic system," added Prof Longo.
"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," Dr Longo said.
"What we started noticing in both our human work and animal work
is that the white blood cell count goes down with prolonged fasting. Then when
you re-feed, the blood cells come back. So we started thinking, well, where
does it come from?"
Fasting for 72 hours also protected cancer patients against the toxic
impact of chemotherapy.
"While chemotherapy saves lives, it causes significant collateral
damage to the immune system. The results of this study suggest that fasting may
mitigate some of the harmful effects of chemotherapy," said co-author
Tanya Dorff, assistant professor of clinical medicine at the USC Norris
Comprehensive Cancer Center and Hospital.
"More clinical studies are needed, and any such dietary
intervention should be undertaken only under the guidance of a physician.”
"We are investigating the possibility that these effects are
applicable to many different systems and organs, not just the immune
system," added Prof Longo.
However, some British experts were sceptical of the research.
Dr Graham Rook, emeritus professor of immunology at University College
London, said the study sounded "improbable".
Chris Mason, Professor of Regenerative Medicine at UCL, said: “There
is some interesting data here. It sees that fasting reduces the number and size
of cells and then re-feeding at 72 hours saw a rebound.
“That could be potentially useful because that is not such a long time
that it would be terribly harmful to someone with cancer.
“But I think the most sensible way forward would be to synthesize this
effect with drugs. I am not sure fasting is the best idea. People are better
eating on a regular basis.”
Dr Longo added: “There is no evidence at all that fasting would be
dangerous while there is strong evidence that it is beneficial.
“I have received emails from hundreds of cancer patients who have
combined chemo with fasting, many with the assistance of the oncologists.
“Thus far the great majority have reported doing very well and only a
few have reported some side effects including fainting and a temporary increase
in liver markers. Clearly we need to finish the clinical trials, but it looks
very promising.”
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