Does melatonin support your immune system in later life?

As we age, melatonin production declines, and that decline goes hand in hand with a gradual deterioration of the immune system. At the same time, a pro-inflammatory mechanism in the body becomes overactive, contributing to low-grade chronic inflammation that plays a role in age-related diseases. Whether falling melatonin actually causes these problems, or merely correlates with them, has not yet been established.

In laboratory and animal research, melatonin has clear effects on the immune system. It stimulates natural killer cells (immune cells that attack viruses and cancer cells) and T-helper cells, and increases the release of immune signalling molecules. Mouse studies also show that melatonin protects older animals better against infections and cancer, and that the shrinkage of the thymus (the organ in which T-cells mature) may be slowed. These are, however, animal and laboratory findings, and the translation to humans remains insufficiently substantiated.

The idea that melatonin can counteract inflammaging (low-grade age-related inflammation) and muscle loss is theoretically interesting: as an antioxidant and cellular cleanser it could be a candidate for this role. But this reasoning is primarily mechanistic. Clinical evidence in humans is still thin.

Melatonin is already being used for sleep disorders in older age. Sleep deprivation weakens the immune system, so better sleep may be indirectly beneficial. Direct evidence that melatonin supplements measurably improve immune function in older people is, however, absent from the available studies.

If you are considering melatonin as a sleep aid, its safety with short-term use in older adults is reasonably well documented. As an immune-boosting supplement, it is too early to have concrete expectations of it at this point.