Safety concerns regarding impurities in L-Tryptophan associated with eosinophilia myalgia syndrome

• Published in: Food and chemical toxicology 2023-09, Vol.179, p.113946-113946, Article 113946
• Main Authors: Ko, Soo Min, Park, Ji-Eun, Heo, In Kyung, Shin, Yong Uk, Kim, Yang Hee, Son, Woo-Chan
• Format: Article
• Language: English
• Subjects: Dietary supplement; Eosinophilia-myalgia syndrome; Feed additive; L-tryptophan; Safety
• ISSN: 0278-6915; 1873-6351
• DOI: 10.1016/j.fct.2023.113946

L-tryptophan is one of the essential amino acids in humans and across the animal kingdom. It has been widely used as a feed additive for domestic animals and is also administered through dietary supplements in humans. Safety concerns have been raised however since a disease known as eosinophilia-myalgia syndrome (EMS) was reported to be related to L-tryptophan supplements. EMS is a rare condition characterized by inflammation in various organ systems including the muscles, skin, and lungs. Through several studies, it has been speculated that the six components generated during the process of L-tryptophan synthesis are related to the induction of EMS. In this review, we discuss the history of EMS and its controversial correlation with L-tryptophan use reported in several studies. Many in vitro and in vivo studies have been conducted to assess the putative correlation between impurities in L-tryptophan preparations and EMS, but no clear and convincing conclusions have been drawn so far. •The outbreak of eosinophilia-myalgia syndrome was known be induced by L-tryptophan.•Six impurities were found to be associated with eosinophilia-myalgia syndrome.•Safety concerns of L-tryptophan are due to its production by certain bacteria.•Safety concerns of L-tryptophan are debatable based on the prior animal studies.