Tryptophan
L-Tryptophan
L-Tryptophan is an essential amino acid that serves as the primary dietary precursor to serotonin, melatonin, and niacin (vitamin B3). It is widely used as a supplement to support mood regulation, improve sleep quality, and reduce anxiety, particularly in individuals with low serotonin activity or poor dietary intake.
Mechanism of Action
Tryptophan is converted in the brain to 5-hydroxytryptophan (5-HTP) via tryptophan hydroxylase, and then to serotonin (5-HT), a key neurotransmitter regulating mood, appetite, and cognition. Serotonin is subsequently converted to melatonin by the pineal gland, linking tryptophan intake directly to circadian rhythm regulation. A competing metabolic pathway via IDO (indoleamine 2,3-dioxygenase) diverts tryptophan toward kynurenine and niacin synthesis, particularly under inflammatory conditions.
Evidence by Health Goal(17 goals)
Dosing Protocols
30-60 minutes before bed, on an empty stomach or with a small carbohydrate snack
Carbohydrates enhance brain uptake by reducing competition from other large neutral amino acids. For mood support, doses can be split into 500mg 2-3x daily. Start at the lower end (500mg) and titrate upward. Doses above 3g/day are generally not recommended without medical supervision.
Safety & Side Effects
L-Tryptophan has a generally favorable safety profile at recommended doses (500-2000mg/day) and has been used therapeutically for decades. However, it carries a serious risk of serotonin syndrome when combined with SSRIs, MAOIs, or other serotonergic drugs, and should not be used alongside these medications without physician oversight.
Possible Side Effects
- !Drowsiness and sedation, especially at doses above 1g
- !Nausea and gastrointestinal discomfort at higher doses (>2g)
- !Headache, particularly when combined with serotonergic agents
- !Dizziness or lightheadedness
- !Dry mouth
- !Eosinophilia-myalgia syndrome (EMS) — rare, historically linked to contaminated batches from specific manufacturers
- !Vivid dreams or altered dream states
Interactions
- -Contraindicated with MAOIs — risk of severe serotonin syndrome, potentially life-threatening
- -SSRIs and SNRIs (e.g., fluoxetine, venlafaxine) — additive serotonergic effect increases serotonin syndrome risk
- -5-HTP supplementation — synergistic serotonin precursor effect; combined use significantly elevates serotonin syndrome risk
- -Carbidopa (used in Parkinson's therapy) — inhibits peripheral tryptophan metabolism, increasing central conversion and serotonin levels unpredictably
- -Sedatives, benzodiazepines, and sleep aids — additive CNS depressant effects when taken at bedtime doses
Cost & Where to Buy
Widely available OTC in capsule or powder form. Bulk powder is significantly cheaper; branded capsule formulations cost more. Quality USP-verified or pharmaceutical-grade products sit at the higher end of the range.
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