Amino acids & related
Tryptophan
Names you may see: L-tryptophan serotonin
The quick take
Tryptophan is an essential amino acid used to make proteins and involved in producing serotonin, melatonin and niacin.
A closer look
What forms will I see on a label?
Dietary protein and isolated L-tryptophan supplements are different sources. It is also distinct from 5-HTP.
Why people use it
Supplement companies market isolated tryptophan for relaxation, sleep and a positive mood. This is a different use from obtaining tryptophan through ordinary dietary protein.
These are common goals and marketing uses. The evidence section below explains what research supports.
What does the evidence tell us?
Its biochemical role does not mean every tryptophan-containing protein product is a sleep treatment. Product amount, formulation and the intended use matter.
What should I know before using it?
Discuss isolated tryptophan with a pharmacist before combining it with medicines or other supplements.
Sources & further reading
MedlinePlus ingredient information ↗
Content reviewed: September 30, 2026
General educational information. Follow the product label and seek individual advice when needed.