The Serotonin Connection with Sleep

We know from the research that serotonin plays a key role in sleep. Studies have shown that both low serotonin and low tryptophan can result in:

. Difficulty getting to sleep

. More interruptions in sleep

. Less quality sleep (less deep REM sleep)

. More time awake

Serotonin is made in the body from the nutrient tryptophan. To have adequate serotonin levels, tryptophan must either be available in the diet or in supplement form. Tryptophan is also the raw material that is converted to melatonin, the master hormone that starts the process of going to sleep.

As the precursor to both serotonin and melatonin, tryptophan supports sleep in at least two important ways:

. Adequate serotonin promotes relaxation and reduces tension

. Melatonin provides the signal that initiates sleep

The role of tryptophan in sleep has been well established through numerous studies. Researchers have also found that supplementing tryptophan improves the quality of sleep and promotes sleep in cases of chronic insomnia.

Low Tryptophan and Sleep Problems

. When tryptophan is low, quality sleep is delayed

The effects of tryptophan depletion on sleep were studied by researchers at the Center for Clinical Investigation in Paris : "Because serotonin is involved in the regulation of sleep cycles, we tested the effect of midmorning tryptophan depletion on the next night's sleep. [Deep] REM sleep was delayed by about 20 minutes and sleep fragmentation increased by about 60%."

I Arnulf and others. "Mid-morning tryptophan depletion delays REM sleep onset in healthy subjects." Neuropsychopharmacology. November 2002; Vol 27, No 5: pages 843-851.

. Tryptophan depletion increases time awake

Researchers at the University Hospital of Freiburg in Germany studied the effects of tryptophan depletion on the metabolism of serotonin in the brain. "Because serotonin is involved in sleep regulation and the regulation of [mood] on sleep, we studied the acute effects of tryptophan depletion and expected to induce similar changes in sleep patterns similar to those observed in depressed patients." Tryptophan depletion was found to cause significant effects on sleep including an increased percentage of time awake and changes in sleep patterns.

U Voderholzer and others. "Impact of experimentally induced serotonin deficiency by tryptophan depletion on sleep EEG in healthy subjects." Neuropsychopharmacology. February 1998; Vol 18, No 2: pages 112-124

. Tryptophan depletion lowers melatonin

At the Connecticut Mental Health Center in New Haven , Connecticut , researchers studied the essential amino acid tryptophan which is the precursor for both serotonin and melatonin. To determine the effects of serotonin functions on night-time melatonin secretion, eight healthy volunteers underwent tryptophan depletion. Researchers reported that tryptophan levels in the blood decreased to less than 20% of initial levels. After tryptophan depletion, melatonin secretion was decreased in all eight subjects. The conclusion: "These results suggest that reduced tryptophan levels, and presumably brain serotonin concentrations, decrease nocturnal melatonin secretion in humans."

RC Zimmermann and others. "Effects of acute tryptophan depletion on nocturnal melatonin secretion in humans." Journal of Clinical Endocrinology and Metabolism . May 1993; Vol 76, No 5: pages 1160-1164.

Benefits of Supplementing Tryptophan

.Supplementing tryptophan promotes deep, quality sleep

One of the early studies of tryptophan evaluated the effect of L-tryptophan on night-time and day-time sleep in healthy males when tryptophan was supplemented. "Analysis of the sleep measures suggested reduced awakenings, increased stage 3 [sleep] and an increased percentage of [deep] REM sleep."

AN Nicholson and BM Stone BM. "L-tryptophan and sleep in healthy men." Electroencephalography in Clinical Neurophysiology . November 1979; Vol 47, No 5: pages 539-545.

. Tryptophan reduces problems with getting to sleep

At the University of Manitoba in Canada , researchers evaluated the effects of tryptophan on sleep. Their review pointed out that tryptophan is readily converted to serotonin, which is thought to be important in slow wave sleep and possibly deep REM sleep (sleep with rapid eye movement). They measured the effects of L-tryptophan on objective and subjective measures of sleepiness and examined their relationship to blood L-tryptophan levels in ten healthy volunteers. "We conclude that L-tryptophan consistently reduced sleep [delay] in normal [subjects] and that this correlates with blood levels."

CF George and others. " The effect of L-tryptophan on daytime sleep latency in normals: correlation with blood levels." Sleep. August 1989; Vol 12, No 4: pages 345-353

. Tryptophan promotes sleep in cases of chronic insomnia

At the Department of Psychiatry of the University of Frankfurt , thirty-nine subjects with chronic persistent insomnia were treated with L-tryptophan. Researchers reported: "On the basis of subjective ratings, it appears that L-tryptophan is effective in promoting sleep in cases of chronic insomnia."

K Demisch and others. " Treatment of severe chronic insomnia with L-tryptophan: results of a double-blind cross-over study." Pharmacopsychiatry. November 1987; Vol 20, No 6: pages 242-244.