A Medical Letter reader asked about the use of the nutritional supplement 5-hydroxytryptophan (5-HTP) for treatment of depression. It is sold in health food stores, pharmacies and on-line for many indications including depression, mood enhancement, emotional well being, and promotion of normal sleep.

5-HTP is the intermediate metabolite in the biosynthesis of serotonin from L-tryptophan.1 Many small studies in the 1970’s and 1980’s found 5-HTP helpful in the treatment of depression, but a Cochrane Review of 108 studies in patients with depression or dysthymia using 5-HTP or L-tryptophan found that the quality of the data was insufficient to establish the efficacy or safety of these products.2

In 1989, contaminated L-tryptophan supplements were implicated as the causative agent in an outbreak of eosinophilia-myalgia syndrome (EMS), which was associated with some deaths. There is no evidence that 5-HTP could cause the syndrome.

There is no acceptable evidence that 5-HTP or L-tryptophan offers any advantage over a selective-serotonin reuptake inhibitor (SSRI) for treatment of depression. Taking 5-HTP or L-tryptophan in addition to an SSRI could cause serotonin syndrome.

There is no good reason to take 5-HTP or L-tryptophan.