There are many benefits of intermittent fasting that are not always well understood. But researchers have noticed something quite surprising: through a complex mechanism, fasting promotes nerve regeneration in mice. Intermittent fasting consists of an alternating period of fasting followed by a period of eating – both periods varying in length depending on the schedule. For example, food consumption may be spread over eight hours and fasting over sixteen hours. Proponents of the practice attribute many virtues to it, some of which have not been scientifically confirmed. Nevertheless, it is a subject of great interest to researchers, and some of its benefits have been carefully examined.
The most recent one is not about weight or inflammatory diseases, but about nerve regeneration. A team at Imperial College London observed that fasting promotes sciatic nerve repair after injury in laboratory mice. But this is only possible with the help of a third player: the microbiota.
Fasting to heal nerves
Nerves are part of the peripheral nervous system and innervate the whole body to transmit information from the extremities to the brain. They are made up of axons, which are extensions of neurons, and regenerate quite slowly after injury. Nerve damage is therefore quite difficult to treat, except for surgery, which is only possible for a minority of patients. But lifestyle changes such as exercise have been shown to improve nerve regeneration. And now intermittent fasting can do the same.
“Intermittent fasting has previously been linked in other studies to healing and the growth of new neurons, but our study is the first to explain exactly how fasting can promote nerve healing,” explains Simone Di Giovanni, a neuroscience researcher at Imperial College.
IPA, a key molecule secreted by the microbiota
Researchers at Imperial College London have uncovered a fairly detailed mechanism. Here it is. Fasting mice have high levels of indole-3-propionic acid (IPA) in their blood, a molecule that stimulates nerve renewal. It’s not an organ that secretes it, but Clostridium sporogenes, a bacterium found in the gut microbiota. “When IPA cannot be produced by these bacteria and is almost absent from the serum, regeneration is impaired. This suggests that the IPA generated by these bacteria has the ability to heal and regenerate damaged nerves,” continues Simone Di Giovanni. The length of regenerated axons is about 50% longer in fasting mice than in continuously fed mice. When IPA is administered orally to rodents, the benefits of nerve regeneration become evident after two to three weeks.
After these promising observations, questions remain: do they hold true in humans? Can IPA help regenerate other nerve structures, such as the spinal cord? Can IPA have an effect in combination with a conventional non-fasting diet? These are questions researchers are likely to try to answer.