From the Guidelines
Prolonged fasting does stimulate the regeneration of immune cells, specifically white blood cells (leukocytes), and may enhance certain aspects of immune function, but its effects should be considered with caution and under medical supervision. The current understanding of fasting's impact on immune regeneration is based on studies that show caloric restriction and fasting can drastically reduce IIS and mTOR signaling, increase lifespan in many species, and improve cardiometabolic parameters in humans 1. During extended fasting, the body initially reduces white blood cell counts, followed by regeneration of new immune cells when refeeding occurs, a process that involves autophagy and stem cell activation.
The mechanisms behind fasting's effects on immune cells likely involve reduced IGF-1 levels and increased autophagy during fasting periods, as suggested by research on caloric restriction and its benefits on aging-related diseases 1. However, it's crucial to consider that while fasting may offer some immune benefits, extended fasting should not be undertaken without medical supervision, especially for individuals with existing health conditions, as it can also stress the body and potentially compromise immune function if done improperly or for too long.
Key points to consider include:
- The regenerative effects of fasting on immune cells are part of its complex physiological impacts, which can include improved cardiovascular markers and potentially beneficial effects in the treatment of cancer by making tumor cells more vulnerable to chemotherapy 1.
- The research in humans is still limited, with most compelling evidence coming from animal studies, highlighting the need for further investigation into the long-term effects of fasting on aging-related diseases in humans 1.
- Fasting could be especially beneficial in certain contexts, such as the treatment of cancer, by improving the regeneration of the immune system after chemotherapy, but this requires careful consideration and medical oversight 1.
From the Research
Prolonged Fasting and Immune Cell Regeneration
- Prolonged fasting has been shown to stimulate the regeneration of immune cells, specifically white blood cells (leukocytes), and enhance immune function 2, 3, 4.
- Studies have found that prolonged fasting reduces circulating IGF-1 levels and PKA activity, leading to signal transduction changes in long-term hematopoietic stem cells (LT-HSCs) and niche cells that promote stress resistance, self-renewal, and lineage-balanced regeneration 2.
- Multiple cycles of fasting have been found to abate immunosuppression and mortality caused by chemotherapy and reverse age-dependent myeloid-bias in mice 2, 4.
Effects of Short-Term Intensive Fasting on Immune Function
- Short-term intensive fasting has been found to enhance autophagy levels and increase leukocyte viability by upregulating key members involved in the upstream signals and within the autophagy machinery 3.
- Short-term intensive fasting has also been found to increase neutrophil degranulation and cytokine secretion, suggesting a boost in immune function, particularly innate immune function 3.
- Additionally, short-term intensive fasting has been found to enhance the immune function of red blood cells in humans, making them more capable of defending against infectious diseases 5.
Mechanisms of Fasting-Induced Immune Cell Regeneration
- The mechanisms of fasting-induced immune cell regeneration are complex and involve the reduction of IGF-1 levels and PKA activity, which leads to changes in signal transduction in LT-HSCs and niche cells 2, 4.
- Fasting has also been found to activate lymphocyte-dependent killing of cancer cells and reduce autoimmunity, although the mechanisms remain poorly understood 6.