Omega-3 fatty acid supplementation affects tryptophan metabolism during a 12-week endurance training in amateur runners: a randomized controlled trial

Abstract The effects of long-term omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation during endurance training on tryptophan (Trp) metabolism and mental state of healthy individuals have not been evaluated so far. Concentrations of plasma Trp, its metabolites and IL-6 were assessed in 26 male runners before and after a 12-week training program combined with supplementation of n-3 PUFAs (O-3 + TRAIN group) or medium chain triglycerides (MCTs; TRAIN group). After the 12-week program participants' mood before and after stress induction was also assessed. The effects of the same supplementation protocol were evaluated also in 14 inactive subjects (O-3 + SEDEN group). Concentrations of 3-hydroxykynurenine (3-HK) and picolinic acid (PA) significantly increased only in the O-3 + TRAIN group (p = 0. 01; ₏^2 η p 2 = 0. 22 and p = 0. 01; ₏ ^2 η p 2 = 0. 26). Favorable, but not statistically significant changes in the concentrations of kynurenic acid (KYNA) (p = 0. 06; ₏ ^2 η p 2 = 0. 14), xanthurenic acid (XA) (p = 0. 07; ₏ ^2 η p 2 = 0. 13) and 3-hydroxyanthranilic acid (3-HAA) (p = 0. 06; ₏ ^2 η p 2 = 0. 15) and in the ratio of neurotoxic to neuroprotective metabolites were seen also only in the O-3 + TRAIN group. No changes in mood and IL-6 concentrations were observed in either group. Supplementation with n-3 PUFAs during endurance training has beneficial effects on Trp's neuroprotective metabolites. Trial registry: This study was registered at ClinicalTrials. gov with identifier NCT05520437 (14/07/2021 first trial registration and 2018/31/N/NZ7/02962 second trial registration).