Fasting Found to Damage Immune Cells

Fasting has become increasingly popular due to its proposed health benefits, but new research by the Icahn School of Medicine at Mount Sinai suggests that fasting may actually have adverse effects on the immune system and could, in turn, increase the risk of heart disease. The study, which focused on mouse models, demonstrated that skipping meals triggers a response in the brain that negatively affects immune cells.

The researchers aimed to understand how fasting affects the immune system, from a few hours to a 24-hour fast. They examined two groups of mice, one that had breakfast immediately after waking up and the other that did not have breakfast. Researchers collected blood samples from both groups at different time points to assess changes in the immune system.

The results showed that, after four hours, the number of monocytes decreased by 90% in the mice that fasted. In fasting mice, the monocytes migrated back to the bone marrow, where they hibernated, and the new cell production in bone marrow diminished. The monocytes that stayed within the bone marrow also aged differently than those traveling through the bloodstream.

When the fasting mice were reintroduced to food, the monocytes in the bone marrow surged back into the bloodstream, leading to heightened levels of inflammation. The altered monocytes were more inflammatory, making the body less resistant to fighting infections. The researchers discovered that specific regions in the brain controlled the monocyte response during fasting. This study demonstrated that fasting elicits a stress response in the brain, which triggers a large-scale migration of these white blood cells from the blood to the bone marrow and back to the bloodstream shortly after food is reintroduced.

Study lead author Dr. Filip Swirski emphasized that, while there is evidence of metabolic benefits of fasting, this new study is a valuable advance in fully understanding the body’s mechanisms. Fasting regulates these cells in ways that are not always beneficial to fight infections, heart disease, or cancer. Diet influences physiology, and this study shows that a diet’s temporal dynamic balance modulates monocyte lifespan with particular consequences for stress adaptation.

These findings highlight the importance of understanding the full impact of fasting on the body, including potential risks. More research is needed to fully understand the effects of fasting on human health. Still, this study provides insight into the possible consequences of fasting on the immune system and the body’s response to external stressors.