Sleep problems are not only very common but are also a culprit in many chronic diseases. L-tryptophan is a dietary and essential amino acid that is converted to serotonin and has attracted the attention of researchers for possible improvement of depression, anxiety, and mood. However, L-tryptophan is also converted to melatonin, the sleep hormone — can it improve sleep as well?

The study

In this systematic review of 18 studies, the participants usually took tryptophan 20 to 30 minutes before bedtime in doses ranging from 0.25 to 15 grams. The mean duration of the intervention was 5.5 days. Of the 18 studies, only 4 were included in the final meta-analysis.

The primary outcomes measured were wake after sleep onset (WASO; any time spent awake in the night after falling asleep), sleep efficiency (percentage of time actually spent asleep during the time spent in bed), amount of REM sleep, and sleep latency (time spent falling asleep).

The results

Tryptophan decreased WASO in the 4 studies included in the meta-analysis. This effect was dose dependent, with every gram of tryptophan reducing WASO by 81 minutes. Tryptophan did not affect other measures of sleep quality.

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This Study Summary was published on June 4, 2021.