Supplement · Protein & amino acids
L-Tryptophan
Also known as: Tryptophan
A serotonin precursor taken for mood and sleep, with modest evidence.
- Evidence
- Silver· human data
- Sources cited
- 1
- Last reviewed
- 22 July 2026
Tryptophan is an essential amino acid and the precursor the body uses to make serotonin and, downstream, melatonin. This underpins its use for mood and sleep support.
There is some human evidence that supplemental tryptophan can modestly aid sleep onset and mood, but studies are mixed and effects are gentle. It is not a sedative, and as with any serotonin-affecting supplement it should not be combined with antidepressants or other serotonergic drugs without medical advice.