Mount Sinai Research Finds Skipping Breakfast May Compromise the Immune System

Skipping breakfast has been found to have potential negative effects on the immune system, according to research conducted at the Icahn School of Medicine at Mount Sinai. The study, which used mouse models, revealed that fasting can lead to unfavorable changes in immune cells and may increase the risk of heart disease.

The recent study conducted by the Icahn School of Medicine at Mount Sinai suggests that fasting can have detrimental effects on immune cells, potentially raising the risk of infection and heart disease.

The findings indicate that fasting could compromise the body’s ability to fight off infections and increase the likelihood of heart disease. The study, focusing on mouse models, is one of the first to demonstrate that skipping meals triggers a response in the brain that negatively impacts immune cells. The results, which specifically investigate the impact of skipping breakfast, have been published in the journal Immunity and contribute to a deeper understanding of the long-term effects of chronic fasting on the body.

“While there is a growing awareness of the health benefits of fasting, our study serves as a cautionary note by suggesting that there may also be health risks associated with fasting,” warns Filip Swirski, PhD, the lead author of the study and Director of the Cardiovascular Research Institute at Icahn Mount Sinai. “Our research delves into the fundamental biology of fasting, revealing a connection between the nervous and immune systems.”

The researchers aimed to gain insight into how different fasting durations, ranging from a few hours to a 24-hour fast, affect the immune system. They conducted their analysis using two groups of mice: one group consumed breakfast as their largest meal upon waking, while the other group skipped breakfast altogether. Blood samples were collected from both groups at baseline (upon waking), four hours later, and eight hours later.

The results of the blood analysis showed a distinct difference in the fasting group. Notably, the number of monocytes, white blood cells that play critical roles in fighting infections, heart disease, and cancer, was significantly affected. Within four hours, 90% of monocytes disappeared from the bloodstream in the fasting group, with a further decline observed at the eight-hour mark. In contrast, the non-fasting group’s monocytes remained unaffected.

In fasting mice, the researchers observed that monocytes migrated back to the bone marrow to hibernate, resulting in reduced production of new cells in the bone marrow. The monocytes in the bone marrow, which typically have a short lifespan, exhibited significant changes. They survived longer due to their prolonged stay in the bone marrow and aged differently compared to the monocytes that remained in the blood.

Furthermore, when the fasting mice were reintroduced to food after up to 24 hours of fasting, the monocytes hidden in the bone marrow rapidly reentered the bloodstream within a few hours. This surge in monocytes led to heightened inflammation, making the body less resilient in fighting infections. These altered monocytes, instead of offering protection against infection, became more inflammatory.

The study sheds light on the brain’s role in the interaction with immune cells during fasting, identifying specific brain regions responsible for controlling the monocyte response. The researchers discovered that fasting triggers a stress response in the brain, which explains the phenomenon of feeling “hangry” (hungry and angry). This response triggers a large-scale migration of white blood cells from the blood to the bone marrow and their subsequent return to the bloodstream after food reintroduction.

Dr. Swirski emphasizes that while there is evidence of metabolic benefits associated with fasting, this study contributes to a better understanding of the body’s mechanisms. “Fasting reduces the number of circulating monocytes, which can be seen as a positive effect as these cells play a role in inflammation. However, the reintroduction of food causes a surge of monocytes back into the blood, which can be problematic. Fasting regulates this pool in ways that are not always beneficial for the body’s ability to respond to challenges such as infections,” explains Dr. Swirski. “Understanding how the function of these cells is controlled is critical, given their importance in other diseases like heart disease or cancer.”

The study was funded by grants from the National Institutes of Health and the Cure Alzheimer’s Fund.

Reference: “Monocytes re-enter the bone marrow during fasting and alter the host response to infection” by Henrike Janssen, Florian Kahles, Dan Liu, Jeffrey Downey, Laura L. Koekkoek, Vladimir Roudko, Darwin D’Souza, Cameron S. McAlpine, Lennard Halle, Wolfram C. Poller, Christopher T. Chan, Shun He, John E. Mindur, Máté G. Kiss, Sumnima Singh, Atsushi Anzai, Yoshiko Iwamoto, Rainer H. Kohler, Kashish Chetal, Ruslan I. Sadreyev, Ralph Weissleder, Seunghee Kim-Schulze, Miriam Merad, Matthias Nahrendorf, and Filip K. Swirski, 23 February 2023, Immunity.
DOI: 10.1016/j.immuni.2023.01.024

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• Mount Sinai School of Medicine: Link
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• Cure Alzheimer’s Fund: Link