Serotonin is a neurotransmitter that the body uses to send messages between nerve cells. When there is a low concentration of this substance in the body, it can cause a bad mood, difficulty sleeping, anxiety or even depression.
You can't get serotonin directly from food, but you can get tryptophan, an amino acid converted to serotonin in the brain. It is mainly found in protein-rich foods, such as turkey, salmon, and tofu. Spending time in the sun appears to increase serotonin levels.