L-tryptophan
Essential amino acid and one-step-upstream serotonin precursor: small RCTs for sleep onset and subjective mood.
Why
L-tryptophan is the essential amino acid from which serotonin and melatonin are synthesised. Older small RCTs from the 1970s and 1980s reported reductions in sleep-onset latency at doses of 1–2 g near bedtime. The Cochrane review of tryptophan and 5-HTP for depression found a similar small-effect pattern. Modern use is constrained by the 1989 contaminated-batch eosinophilia-myalgia incident: quality sourcing is the practical limit.
How it works
Transported across the blood-brain barrier in competition with other large neutral amino acids: the LNAA ratio matters. Hydroxylated to 5-HTP and then decarboxylated to serotonin; further N-acetylated and methylated to melatonin in the pineal gland.
Expected onset · Sleep-onset effects often the same night; subjective mood effects over 1–2 weeks
How to take
Dosage
Sleep: 1–2 g 30–60 min before bed, away from protein meals (which compete for LNAA transport). Mood: 1–3 g/day divided.
Timing
Bedtime, away from protein meals; pair with a small carbohydrate snack to favour transport
On the label
'L-tryptophan' (not 'tryptophan complex'), pharmaceutical-grade, with stated purity. Avoid bulk powder of uncertain provenance.
Ideal for
Adults with mild sleep-onset complaints; people exploring nutrient approaches to mood under clinical guidance.
Safety
Evidence
Cochrane 2002 SR found small antidepressant effect signal for tryptophan + 5-HTP, but low trial quality limited the conclusion. Older sleep-onset RCTs (Hartmann 1982 and others) reported reduced sleep latency at 1–2 g, but evidence base is dated and predominantly from open or small trials. Mechanistic plausibility is high; modern RCT quality is the gap.
Where to get it
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