Tryptophan

An essential amino acid precursor to serotonin (mood neurotransmitter) and melatonin (sleep hormone). Its conversion to serotonin is improved by the simultaneous presence of carbohydrates in the meal: the insulin secreted facilitates tryptophan's entry into the brain by reducing competition from other amino acids. Main sources: turkey (most concentrated), chicken, pumpkin seeds, hemp seeds. Tryptophan deficiency is associated with reduced serotonin synthesis and mood disorders.