Synopsis

Source of validity: Scientific
Rating (out of 5): 3

L-tryptophan is an essential amino acid that serves as a precursor to serotonin, a neurotransmitter involved in the regulation of mood, sleep, and appetite. Serotonin itself is a precursor to melatonin, the hormone that regulates the sleep-wake cycle. The scientific rationale for using L-tryptophan to support sleep, particularly in cases of restlessness and disturbed sleep, is based on its role in these biochemical pathways.

Clinical studies have investigated the effects of L-tryptophan supplementation on sleep. Several small-scale studies from the 1970s and 1980s found that L-tryptophan (in doses ranging from 1 to 5 grams) can reduce the time it takes to fall asleep and may improve subjective sleep quality, particularly in individuals with mild insomnia or sleep disturbances. The evidence suggests that L-tryptophan supplementation can increase melatonin production, thereby facilitating sleep onset and improving overall sleep continuity.

However, the quality and size of available studies are variable, and some more recent research has produced mixed results. Most studies indicate only modest benefits, and the effects appear to be most significant in people with mild to moderate sleep disturbances rather than severe insomnia. Major medical organizations do not universally recommend L-tryptophan as a first-line treatment for sleep disorders, but acknowledge its potential utility. Safety concerns, especially those arising from past contamination incidents (e.g., eosinophilia-myalgia syndrome in the late 1980s), led to temporary restrictions, but pure L-tryptophan is considered generally safe when used appropriately.

Overall, there is moderate scientific support for the use of L-tryptophan in improving sleep in certain populations.

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Nature's Sunshine Free Amino Acids