Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.


Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Fasting 'revives immune system'


Fasting for at least two days regenerates immune systems damaged by ageing or cancer treatment, research has shown.

The finding, demonstrated both in mice and cancer patients, has dramatic implications for human health, say scientists.

It shows for the first time that a simple natural intervention can trigger the stem cell-based repair of vital systems in the body.

Fasting had the effect of culling old and damaged immune system cells and replacing them with fresh and more effective new ones.

US lead scientist Professor Valter Longo, director of the University of Southern California’s Longevity Institute, said: “We could not predict that prolonged fasting would have such a remarkable effect in promoting stem cell-based regeneration.

“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.

“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.”

Experiments showed that fasting flipped a switch in bone marrow stem cells causing them to start regenerating themselves.

The “haematopoietic” stem cells develop both into oxygen-carrying red blood cells and the wide range of white blood cells that act as the immune system’s foot soldiers.

But the effect only occurs after going without food for a prolonged period, between two and four days at a time.

After a certain period, fasting forces the body to go into “survival mode”, using up stores of glucose, fat and organic compounds called ketones, and also breaking down excess numbers of “old” white blood cells.

At the same time, a signal is sent to bone marrow stem cells.

“It gives the ‘ok’ for stem cells to go ahead and begin proliferating and rebuild the entire system,” said Prof Longo. “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.

“If you start with a system heavily damaged by chemotherapy or ageing, fasting cycles can generate, literally, a new immune system.”

Both natural ageing and anti-cancer chemotherapy drugs weaken the immune system.

The scientists found that multiple fasting sessions reduced immune system weakening and death in mice exposed a chemotherapy drug. In addition, they rejuvenated the immune systems of ageing mice.

Protection against white blood cell loss was also seen in human cancer patients taking part in a small pilot trial. The patients were asked to fast for a single 72-hour period before undergoing chemotherapy.

Dr Tanya Dorff, also from the University of Southern California, a co-author of the research published in the journal Cell Stem Cell, said: “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.”

The scientists are now exploring the possibility that the same effects of fasting might apply across many biological systems and organs.

A key discovery was that prolonged fasting lowered circulating levels of a growth-promoting protein, Insulin-like Growth Factor 1 (IGF-1) , which has been linked to ageing, tumour progression and cancer risk.


Readers' comments (7)

  • Fasting one of the main pillars of Islam and has been prescribed to all other religions too. I'm glad science is now validating what religion has been advising us to do for centuries now. Ramadan is in less than a month, hope we all make the most it this auspicious occasion.

    Unsuitable or offensive? Report this comment

  • Tomasz Jandzis

    Dear Ray,
    in this article they are talking about 72 hrs not 12 (approx.) :-)

    Unsuitable or offensive? Report this comment

  • michael stone

    I think a lot of religions mention fasting - but as Tomasz Jandzis points out, this isn't about fasting during daylight hours.

    Unsuitable or offensive? Report this comment

  • It's Biblical to fast.Jesus did 40 days and 40 nights.

    Unsuitable or offensive? Report this comment

  • My Husband does the 5:2 diet and fasts for 2 days a week, all it does for him is make very grumpy!! Although fair play he has lost weight, but think I would prefer him with a few extra pounds and happy!

    Unsuitable or offensive? Report this comment

  • michael stone

    Anonymous | 8-Jun-2014 3:39 pm

    That makes you ponder - if the outcome would be be longer-but-grumpier lives, would that be a good thing or not ?

    It reminds me of the old one about 'giving up most of life's pleasures might not make you live longer, but it will certainly feel like it'.

    Unsuitable or offensive? Report this comment

  • It's not bad news if you are seriously ill is it. How fantastic to be able to do something other than take vast amounts of drugs that make you ill. And if it has a really positive effect, well I am sure it would be a joy to do. I don't think you are looking at it from the point of view of someone with a serious illness are you anon.

    Unsuitable or offensive? Report this comment

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Links may be included in your comments but HTML is not permitted.