The dietary supplement 5-hydroxytryptophan and urinary 5-hydroxyindole acetic acid

During an appointment to sign consent for endoscopy of the upper and lower gastrointestinal tract, the patient reported that, for the last 18 months, she had been taking 5- hydroxytryptophan (5-HTP, 100 mg daily, Natural Factors, Coquitlam, BC), which she had purchased from a local health food store. The patient was advised to stop taking this supplement, and a 24-hour urine collection to test for 5-hydroxyindole acetic acid was repeated 2 weeks later. At this time, the 24-hour excretion of 5-hydroxyindole acetic acid was 18 ìmol. Her diarrhea also improved and had not returned 6 months later. We found no dose-response studies of 5-hydroxyindole acetic acid excretion levels in humans following oral ingestion of 5-hydroxytryptophan. However, our patient, who was taking a regular dose of 100 mg of 5-hydroxytryptophan daily, excreted a 5-hydroxyindole acetic acid level 10 times the normal upper limit in 24 hours. We did not assess the actual amount of 5-hydroxytryptophan in the commercial preparation.