Fasting Has Shown Potential Impact In Animal Study


On December 25, 2018, we ran the story below on this page titled, “Study: Fasting For As Little As 3 Days Is Reported To Significantly Help Our Immune System”. This story was widely shared in social media.

On January 19, 2020, we shared the story on our Facebook page,

Unbeknownst to me, the study I had referenced in the article in question (1) was later reviewed by lead study author Dr. Valter Longo, Ph.D., Professor of Biological Sciences, Leonard Davis School of Gerontology, University of Southern California and Stefan Jordan, Postdoctoral Fellow, Icahn School of Medicine at Mount Sinai for

Their analysis is below,

The UK Telegraph went to a level of absurdity on this study on June 5, 2014 stating, “Fasting for three days can regenerate the entire immune system, study finds.” (2)

I quoted the Telegraph here when I wrote that, “Fasting for as little as 3 days can help your body to regenerate your entire immune system in people of all ages, according to a recent study published in The Telegraph.”

In reporting here on this highly interesting study, to quote a source like the Telegraph was a mistake since these types of results in animals are not necessarily directly transferable to humans. Therefore, we have added this report as a correction. I apologize for my part since English is not my first language.

As part of the original study, (1) the authors noted, “Our results indicate that cycles of an extreme dietary intervention represent a powerful means to modulate key regulators of cellular protection and tissue regeneration but also provide a potential therapy to reverse or alleviate the immunosuppression or immunosenescence caused by chemotherapy treatment and aging, respectively, and possibly by a variety of diseases affecting the hematopoietic and immune systems and other systems and organs. The clinical data shown here provide preliminary results supporting the possibility that these effects can also be translated into effective clinical applications.”

This demonstrates a very exciting prospect for the future, but to herald such a study as was done by the Telegraph is highly unscientific.

The senior study author Dr. Valter Longo (1) has made several significant points in his subsequent analysis.

The “study was performed in mice, not humans, and so the effects cannot be directly extrapolated to people.”

As well as, “The effects of fasting on immunosuppression have also not been thoroughly studied in healthy people who are not undergoing chemotherapy treatment – it is, therefore, premature to claim that fasting would “regenerate” the immune system for everyone.”

He also noted that, “In humans, we only know that fasting decreases the level of immune cells while re-feeding restores the level of immune cells. This suggests but does not prove that similar regenerative effects will take place in humans.”

Stefan Jordan, Postdoctoral Fellow, Icahn School of Medicine at Mount Sinai noted that:

“The study’s authors discovered that fasting has a pro-regenerative effect on stem cells after chemotherapy. The claim sounds as if one would get a brand new immune system through fasting. It is important to note that prolonged fasting in healthy adults can actually have negative effects on the immune response to infection and after tissue injury, as we reported in our recent study published in Cell.” (3)

In closing, when it comes to science, we must be willing to accept when we’ve made a mistake. I erred in my reporting on this study and have corrected my article to set the record straight.

1. Cheng et al. (2014) Prolonged Fasting Reduces IGF-1/PKA to Promote Hematopoietic-Stem-Cell-Based Regeneration and Reverse Immunosuppression. Cell Stem Cell.


3. Wang et al. (2016) Opposing Effects of Fasting Metabolism on Tissue Tolerance in Bacterial and Viral Inflammation. Cell.

Fasting is considered to be one of the secrets of maintaining good health since ancient times. It has been practiced throughout all of the human civilizations for as long as history can remember. Today, this habit can be considered a secret because it has been apparently forgotten.

Recently, many people around the world are re-discovering this ancient dietary procedure because of its numerous health benefits “if it is done right”. Among the health benefits include increased energy, weight loss, the reversal of type-2 diabetes, and a lot more. Another good thing about this process is you’ll get to save time and money.

An animal study conducted by researchers at the University of Southern California has provided some potential significance in this area.

The research provided facts that fasting boosts up the stem cells into producing new white blood cells, which wards off foreign invaders in the human body such as germs and bacteria. This dietary process may someday benefit people suffering from a damaged immune system and this includes those elderly people whose immune system is gradually becoming less effective throughout the years and also cancer patients who went through chemotherapy treatments – which is not really as effective as advertised. In fact, the percentage of successful chemo treatment has been reported as low as 3%. (1)

“In both mice and a Phase 1 human clinical trial involving patients receiving chemotherapy, long periods of not eating significantly lowered white blood cell counts. In mice, fasting cycles then “flipped a regenerative switch,” changing the signaling pathways for hematopoietic stem cells, which are responsible for the generation of blood and immune systems, the research showed.” (2)

Valter Longo, the corresponding author of the study and a professor at the USC Davis School of Gerontology, stated:

“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.” (2)

He further added,

“With a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system.”(2)

  1. Morgan G, Ward R, Barton M. The contribution of cytotoxic chemotherapy to 5-year survival in adult malignancies. Clin Oncol (R Coll Radiol) 2004;16(8):549–560. The Contribution Of Cytotoxic Chemotherapy To 5-Year Survival In Adult Malignancies
  2. Wu, Suzanne. Fasting triggers stem cell regeneration of damaged, old immune system. USC News, June 5, 2014.