Fasting and other forms of caloric restriction are associated with reduced risk of many chronic diseases. Monocytes, white blood cells that play key roles in the body’s immune response, can contribute to the pathogenesis of chronic inflammatory diseases. Findings from a new study demonstrate that fasting reduces the number of circulating monocytes without compromising immune function.

The authors of the study analyzed blood samples from 12 healthy adults taken at the beginning of the study (baseline), three hours after they ate, and 19 hours after commencing a fast. All the samples were taken at the same time of day (3pm). After fasting, the participants' blood levels of monocytes were markedly lower than after eating. Fasting did not lower blood levels of monocytes below the normal range in people whose baseline levels were already low.

The study was replicated in mice, with a fasting protocol suitable for rodents. The outcome was similar, with monocytes drastically reduced. A longer fast in the mice yielded even more favorable reductions in monocytes in various tissues as well as reductions in several types of leukocytes, including eosinophils, natural killer cells, and T cells.

These findings illuminate the role of dietary intake in the regulation of the body’s immune and inflammatory responses and suggest that fasting and other forms of caloric restriction may be viable strategies to reduce inflammation in chronic disease states.

• Link to study abstract.

• Learn more about the health benefits associated with fasting in our overview article.