Safety of 5-hydroxy- l-tryptophan

Abstract

5-Hydroxy- l-tryptophan (5-HTP) is the immediate precursor in the biosynthesis of 5-hydroxy-tryptamine (5-HT; serotonin) from the essential amino acid l-tryptophan ( l-Trp). The use of l-Trp as a dietary supplement was discontinued in 1989 due to an outbreak of eosinophilia–myalgia syndrome (EMS) that was traced to a contaminated synthetic l-Trp from a single manufacturer. 5-HTP has since become a popular dietary supplement in lieu of the removal of l-Trp from the market. Because of its chemical and biochemical relationship to l-Trp, 5-HTP has been under vigilance by consumers, industry, academia and government for its safety. However, no definitive cases of toxicity have emerged despite the worldwide usage of 5-HTP for last 20 years, with the possible exception of one unresolved case of a Canadian woman. Extensive analyses of several sources of 5-HTP have shown no toxic contaminants similar to those associated with l-Trp, nor the presence of any other significant impurities. A minor chromatographic peak (peak X) reported in some 5-HTP samples lacks credibility due to chromatographic artifacts and infinitesimal concentrations, and has raised undue speculations concerning its chemistry and toxicity.