Effects of L-tryptophan on sleepiness and on sleep.
Level 5 - mechanism / opinion, no new human data
Narrative review of 40 controlled studies without systematic review or meta-analytic methodology
PubMed 6764927 · doi:10.1016/0022-3956(82)90012-7
What was done
This review summarized 40 controlled human studies published over a 20-year period assessing the effects of L-tryptophan on sleepiness and sleep parameters across normal subjects, individuals with mild or severe insomnia, and patients with medical or psychiatric illness.
What was found
The abstract reports that L-tryptophan at doses of 1 g or more increased subjective sleepiness ratings and decreased sleep latency. Less consistent evidence suggested possible decreases in total wakefulness and increases in total sleep time. Benefits were clearest in participants with mild insomnia or normal subjects with longer baseline sleep latency. Mixed or negative findings were noted in completely normal subjects, severe insomniacs, and patients with serious medical or psychiatric conditions. No specific numerical values or statistical metrics were provided in the abstract.
Why it matters
The review characterizes the target population for L-tryptophan, indicating it may help mild sleep-onset latency issues but lacks consistent efficacy for severe insomnia or normal baseline sleepers.
Limits
The abstract describes a narrative review without formal systematic search criteria, quality appraisal, or meta-analytic pooling. Specific participant counts, study protocols, numerical effect sizes, and adverse event data are omitted.
Cited by
- contradicts A person would need to consume a 46-pound turkey to obtain enough tryptophan to induce sleep.