There is a growing awareness that methodical fasting is healthy: there is abundant evidence of the benefits of fasting on cellular well-being. Practicing fasting, in fact, activates a cell survival mechanism called “autophagy”, which literally means “eating oneself”.
In practice this happens: the cells survive by consuming all that they have inside them that is not indispensable, such as malfunctioning intracellular organelles or deposits of mutated proteins and other waste material that can hinder the proper functioning of the cells.
A real decluttering, to put it like nowadays, or the act of getting rid of the superfluous, of everything that is not needed for life. But a new study (in mice) suggests that prolonged fasting may have the potential to boost immunity.
Fasting: the study on mice
The researchers compared mice that could eat whenever they wanted with mice that didn’t have access to food. The research found that there was a rapid reduction in the number of circulating immune cells in animals that weren’t allowed to eat in the hours after they woke up. It was observed that after just four hours of fasting, there was a 90% decrease in the number of monocytes, a type of immune cell, in the bloodstream of fasted mice.
Study: Don’t tell the immune system about prolonged fasting
Monocytes are larger white blood cells, accounting for about 1 to 6% of white blood cells. They are generated from the bone marrow and act like small vigilante patrols in the bloodstream looking for pathogens. When they reach the tissues where their intervention is necessary, they increase in size, differentiate and become macrophages. It is at this point that they “devour” infectious agents (bacterial, fungal, viral) or even residues of dead or damaged cells.
What intrigued the scientists is that during periods of fasting, immune cells returned from the bloodstream to the bone marrow, only to return to the bloodstream after food was ingested. The study thus shows that, on the one hand, fasting reduces the number of circulating monocytes, which one might think is a good thing, since these cells are important components of inflammation.
On the other hand, the reintroduction of food creates a surge of monocytes back into the blood, which can be problematic. It was precisely this return of mass that led to an increase in the level of inflammation (monocytosis). Essentially, instead of protecting against infection, these altered monocytes were more inflammatory, making the body less resistant to fighting infection.
Energy drops, cortisol increases
It’s not all. There is more. As if that weren’t enough, the lack of energy has led to an increase in the synthesis of the stress hormone cortisol. It was precisely on the occasion of the increase in the levels of this hormone that the recall of immune cells by the immune system in the bone marrow was recorded with the aim of better conserving resources in times of scarcity.
Fasting yes, fasting no?
The question arises spontaneously at this point. The answer? It’s in the middle. As often happens, it is also necessary in this case to make an assessment of costs and benefits. Intermittent fasting, i.e. carried out methodically, can have valuable benefits on cellular well-being. However, it is important that it is not extreme, i.e. that the fasting periods are not excessively protracted.
The key therefore may be a non-extreme form of fasting and controlled re-nutrition. It’s too early to tell whether studies like this one in mice have implications for people who skip breakfast or fast to lose weight.
However, studies are not yet sufficient to come to a firm point, but this preliminary evidence shows that the availability of energy can affect the efficiency of the immune system.
A recent study showed that continuously fasting mice for only 12-16 hours improved the immunity of these animals. This suggests that the “cancelling dinner” methods and the 16:8 intermittent fasting formula (Time Restricted Feeding) adopted 2-3 times a week on alternate days could be a good compromise to activate benefits on the cells and at the same time safeguard the immune efficiency.
Bibliography
Chaix A. Et al. Sex- and age-dependent outcomes of 9-hour time-restricted feeding of a Western high-fat high-sucrose diet in C57BL/6J mice. Cell Press, vol. 2 issue 36, 2021.
Janssen H. Et al. Monocytes re-enter the bone marrow during fasting and alter the host response to infection. Immunity, 2023;
Jordan S. Et al. Dietary Intake Regulates the Circulating Inflammatory Monocyte Pool. Cell,178(5):1102-1114.e17, 2019.
