Melatonin: the hormone that induces sleep

Nowadays the lack of sleep can affect every age bracket. All humans are governed by the need to sleep: in fact without sleep we cannot survive. About 10% of adults in the world suffer from severe insomnia. One of the reasons that we have lost an hour and a half of sleep per night on average over the last 50 years is the constant presence of lighting.

The day-night cycle represents one of the most crucial synchronisers of our internal biological clock. We are inundated by blue light without realising it and our brain interprets this exposure as sunlight.

The hormone that induces sleep, Melatonin, is produced naturally in the centre of the brain in the epiphysis (pineal gland). In humans, the secretion of melatonin increases soon after darkness falls; it reaches its peak in the middle of the night (between 2 and 4 in the morning), to then gradually decrease in the last part of the night. The plasmatic concentrations of this hormone vary considerably depending on age: they start decreasing in adults, and especially in the elderly. The continuous fluctuation of serotonin and melatonin levels during the day and night help generate vital rhythms that affect many daily activities. For example, the secretion of many hormones is directly or indirectly affected by serotonin and melatonin.

Melatonin is a hormone that has many effects on various organs and systems of the human body. The beneficial effects induced by melatonin can be summarised as:

Strengthening the immune response and the activity of a number of lymphocytes, cells that provide an anti-inflammatory action;

Stabiliser role in cyclical mood disorders (seasonal affectivity disorders, depression in the winter);

Antiproliferative effect that inhibits the growth of tumours;

Regulating the sleep/wake cycle. Taking melatonin regulates sleep, helping the onset, the duration and the quality, also determining an increased duration of REM sleep, all the while without causing an increase in daytime sleepiness.

Protective effects against premature ageing and reduced cell damage through the neutralisation of free radicals. To this regard it is important to remember how free radicals formed during the day represent a constant threat of aggression especially towards organs made mostly of saturated fats, such as the brain, for example.