Sleep induced by L-tryptophan. Effect of dosages within the normal dietary intake.
Level 2 - randomized trial
Small controlled clinical trial comparing multiple doses to placebo
What was done
In a laboratory study, 15 participants with mild insomnia (defined by self-reported sleep latencies exceeding 30 minutes) were tested to evaluate the sleep-inducing effects of low-dose L-tryptophan. The study compared 1/4 g, 1/2 g, and 1 g doses of L-tryptophan against placebo on measures of sleep latency and sleep architecture.
What was found
One gram of L-tryptophan significantly reduced sleep latency relative to placebo, whereas the 1/4 g and 1/2 g doses produced non-significant trends toward reduced latency. The 1/4 g dose significantly increased Stage IV sleep. Exact numerical values, effect sizes, and p-values were not reported in the abstract.
Why it matters
Prior research established sleep-inducing effects at pharmacological doses (1 to 15 g); this study shows physiological effects at dosages falling within the normal daily dietary intake range of 0.5 to 2 g.
Limits
The sample size was very small (n = 15) and restricted to mild insomniacs. The abstract provides no quantitative data, variance estimates, or details on randomization and blinding protocols. Clinical significance and daytime side effects were not evaluated.
Cited by
- supports A person would need to drink almost half a gallon of warm milk to obtain enough tryptophan to induce sleep.