Toxicology and safety study of L‐tryptophan and its impurities for use in broiler feed

Abstract

L‐tryptophan has been utilized as a feed additive in animal nutrition to improve growth performance, as well as a dietary supplement to alleviate various emotional symptoms in humans. Despite its benefits, concerns regarding its safety arose following the outbreak of eosinophilia‐myalgia syndrome (EMS) among individuals who consumed L‐tryptophan. The causative material of EMS was determined to be not L‐tryptophan itself, but rather L‐tryptophan impurities resulting from a specific manufacturing process. To investigate the effect of L‐tryptophan and its impurities on humans who consume meat products derived from animals that were fed L‐tryptophan and its impurities, an animal study involving broiler chickens was conducted. The animals in test groups were fed diet containing 0.065%–0.073% of L‐tryptophan for 27 days. This study aimed to observe the occurrence of toxicological or EMS‐related symptoms and analyze the residues of L‐tryptophan impurities in meat products. The results indicated that there was no evidence of adverse effects associated with the test substance in the investigated parameters. Furthermore, most of the consumed EMS‐causing L‐tryptophan impurities did not remain in the meat of broiler chickens. Thus, this study demonstrated the safety of L‐tryptophan and some of its impurities as a feed additive.

Toxicology and safety study of L‐tryptophan and its impurities for use in swine

“…Previous studies in Sprague-Dawley rats and broiler chickens showed no adverse effects or EMS-related symptoms after L-tryptophan administration (Ko et al, 2022(Ko et al, , 2024. In a subchronic toxicity study using Sprague-Dawley rats, administration of L-tryptophan was revealed as safe up to 2000 mg/kg/day, with no significant differences between the control and treatment groups.…”