Fasting is increasingly being recognized as a beneficial practice, supported by ample evidence. However, a new study published today urges caution as it highlights potential health risks associated with fasting.
This study examines the underlying biological mechanisms of fasting and uncovers a significant interaction between the nervous and immune systems.
A new study from the Icahn School of Medicine at Mount Sinai suggests that fasting may make it harder to fight off infections and could raise the risk of heart disease.
The study, which focused on mouse models, is one of the first to demonstrate that skipping meals causes the brain to react in a way that harms immune cells.
The findings, which center on breakfast, were published in the Immunity journal today and may help researchers better understand how long-term fasting may influence the body.
Researchers wanted to know more about how fasting, from a mild few-hour fast to a more severe 24-hour fast, affected the immune system.
Two mouse groups were examined. The major meal of the day for one group, breakfast, was had immediately after waking up, whereas breakfast was skipped by the other.
Researchers took blood samples from the mice in both groups at the start of the experiment (baseline), four hours later, and eight hours later.
The fasting group showed a clear change in the blood test, according to the researchers. The quantity of monocytes, which are white blood cells produced in the bone marrow and circulate throughout the body and play a variety of vital functions in everything from fighting infections to heart disease to cancer, was specifically where the researchers saw a difference.
All mice had an equal number of monocytes at the beginning. Monocytes in the mice from the fasting group, however, were significantly impacted after four hours. Ninety percent of these cells were discovered to have vanished from the circulation, and after eight hours, the number continued to fall. The non-fasting group’s monocytes, however, were unaffected.
Researchers found that during fasting, monocytes returned to the bone marrow to hibernate. The bone marrow’s capacity to produce new cells also declined at the same time.
Bone marrow monocytes, which are known for their short lifetime, underwent major alterations. They aged differently than the monocytes that remained in the circulation and lived longer as a result of remaining in the bone marrow.
After fasting the mice for up to 24 hours, the researchers reintroduced food. After a few hours, the cells that were hidden in the bone marrow sprang back into the circulation.
This increase caused the inflammation to increase. These changed monocytes were more inflammatory than anti-infective, weakening the body’s ability to fight infection.
This research is one of the first ones to establish a relationship between the brain and these immune cells while the subjects were fasting. Researchers discovered that some parts of the brain were in charge of regulating the monocyte response to fasting.
This study showed that fasting causes the brain to go into a stress response, which is what causes people to feel “hangry” (hungry and angry), and this immediately causes a large-scale migration of these white blood cells from the blood to the bone marrow, and then back into the bloodstream shortly after food is again introduced.
Although there is evidence that fasting has positive effects on metabolism as well, lead author Dr. Filip Swirski stressed that this new research represents an important step forward in our knowledge of the body’s processes.
The research demonstrates that, on the one hand, fasting decreases the amount of circulating monocytes, which one may consider to be beneficial given that these cells are significant contributors to inflammation. Reintroducing food, on the other hand, causes a spike in the number of monocytes that enter the circulation, which may be dangerous. Hence, fasting controls this pool in ways that aren’t necessarily advantageous to the body’s ability to react to a threat like an illness, according to Dr. Swirski.
Since “these cells are so important to other diseases like heart disease or cancer, understanding how their function is controlled is critical.”
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