TRYPTOPHAN

Tryptophan supplementation has been shown to modestly improve sleep quality and reduce sleep latency, likely via increased brain serotonin and downstream melatonin production. Evidence for mood enhancement is mixed; some trials show benefit in mild depression but effect sizes are small and inconsistent. The kynurenine pathway metabolites of tryptophan are increasingly recognized for roles in inflammation, immune regulation, and psychiatric disorders, with peripheral inflammation shifting metabolism toward neurotoxic kynurenine derivatives. Exercise appears to protect against harmful kynurenine accumulation in the brain by upregulating kynurenine clearance in skeletal muscle. Tryptophan and its metabolites also demonstrate antioxidant properties via Nrf2 pathway activation. The 1989 eosinophilia-myalgia syndrome outbreak was linked to contaminated tryptophan from a single manufacturer, not pure tryptophan itself.