Dieting in healthy women results in a decrease in the availability of tryptophan, the amino-acid precursor of serotonin, for brain serotonin synthesis.
The results indicated that the synthesis of serotonin and melatonin, as well as the innate immune response, can be modulated by oral ingestion of tryptophan.
Research has found a positive correlation between serotonin synthesis and total hours of sunlight during the day. In postmortems of humans, serotonin levels are higher during the summer months than the winter months. Getting a better mood could be as easy as opening the curtains in your otherwise dark room.
To assess the effects of external administration of L- tryptophan on the synthesis of serotonin and melatonin as well as on the immune function of Wistar rats, 300 mg of the amino acid were administered either during daylight (08:00) or at night (20:00) for 5 days.