Tryptophan (L-tryptophan)

Tier 3 — weak evidence · Sleep · Mood · Serotonin precursor

An essential amino acid and direct precursor to serotonin and melatonin. Multiple trials show 1 to 3 grams before bed modestly improves sleep onset. Was pulled from the US market in 1989 after a contaminated batch caused eosinophilia-myalgia syndrome, killing 37 people. Modern manufacturing is safe, but the incident led many to prefer 5-HTP instead. Same serotonin syndrome risk as 5-HTP when combined with antidepressants.

Dose: 500–2,000 mg before bed for sleep; NEVER combine with SSRIs, SNRIs, or MAOIs — serotonin syndrome risk