Reactions 720 - 26 Sep 1998 5-hydroxy-L-tryptophan: an EMS epidemic waiting to happen? US researchers have found the presence of a potentially harmful contaminant described as ‘peak X’ in 5-hydroxy-L-tryptophan products. They are concerned about the potential for another epidemic of eosinophilia myalgia syndrome (EMS), similar to that previously seen with L-tryptophan. In 1989, > 1500 cases of EMS were associated with the use of contaminated L-tryptophan, resulting in about 30 deaths. L-tryptophan was contaminated with a substance similar to ‘peak X’. The FDA subsequently banned the sale of over-the-counter (OTC) L- tryptophan. However, 5-hydroxy-L-tryptophan products are currently freely available OTC and are being recommended for serotonin deficiency syndrome, obesity, headaches and insomnia. Presence of contaminants confirmed According to the researchers, 5-hydroxy-L-tryptophan was associated with a case of EMS in 1991; high- performance liquid chromatography of the product used revealed contamination with ‘peak X’. They subsequently assessed the purity of 6 natural or synthetic 5-hydroxy-L-tryptophan products on the market in the US and found that ‘peak X’ was present in all of the products at levels between 3–15% of that previously found in the 1991 EMS case. The researchers say that the lower levels of ‘peak X’ in the currently available products may explain why there have been no further cases of EMS reported. However, they are concerned that a book on the use of 5-hydroxy- L-tryptophan recommends daily dosages of 300–900mg. They are concerned that if such dosages are taken, this may amount to a level of ingested ‘peak...