L-Tryptophan for Sleep Quality
Evidence for L-tryptophan as a sleep aid is weak: at doses of about 1 gram or more it may modestly reduce the time spent awake after first falling asleep, but it does not reliably improve total sleep time, how fast you fall asleep, or overall sleep efficiency. It should not be treated as a general-purpose sleep aid or a substitute for prescription medication or cognitive behavioral therapy for insomnia.
Why this grade7-layer evidence engine
The grade is held to Weak (Tier C) because the supporting signal is real but narrow and the evidence base is thin. A 2022 systematic review and meta-analysis (PMID 33942088) found that tryptophan shortened wake-after-sleep-onset (WASO) by about 81 minutes per gram (SMD -1.08), with doses of 1 gram or more clearly outperforming smaller doses. Crucially, the same analysis found no benefit for total sleep time, sleep latency, or sleep efficiency, so the effect is limited to one specific outcome.
The clinical trials behind this are small and dated. A 2019 double-blind crossover RCT (PMID 31237183, n=98, 1000 mg) improved objective sleep efficiency and WASO measured by actigraphy, while a 1987 double-blind study in chronic insomnia (PMID 3432357, n=39) showed only subjective improvement and a noted treatment-order effect. The meta-analysis pooled just four trials quantitatively, most with undisclosed funding, which limits confidence.
Regulators and clinics do not endorse a sleep benefit. The EU EFSA rejected a health claim for maintaining normal sleep, concluding no cause-and-effect was established, and the US FDA lists tryptophan only as a nutrient food additive with no approved claim. Major clinic sources (Mayo, Cleveland, Harvard) offered no quotable position. Tryptophan also carries serotonin-syndrome interaction risk with antidepressants and a documented history of contamination-linked eosinophilia-myalgia syndrome, so caution is warranted.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.58
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高階證據未達主導 (0 positive vs 1 negative)，由 raw_score 決定
- tier_strict_requirement_check — | B→C 因 scope.conflation_risk=true 且 L11 獨評較低 (B7-2 tier cap)
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status