Interesting but dangerous: that’s what I heard about L-tryptophan supplements for several years. Research starting in the 1960s was showing that L-tryptophan might be an effective remedy for insomnia.
Then came the tryptophan-related outbreak of eosinophilia-myalgia syndrome (EMS) in 1989, killing 37 people and sickening thousands. The epidemic was traced to contaminated L-tryptophan produced by a single Japanese company, but the United States banned L-tryptophan supplements from 1990 to 2001. Research on L-tryptophan and sleep came to a halt.
Now reviewers of alternative treatments for insomnia are again mentioning L-tryptophan as a substance of interest. Here are the pros and cons.
What It Is
L-tryptophan is an essential amino acid the body requires in order to synthesize proteins and other key molecules. It’s a precursor to serotonin, a neurotransmitter important to sleep, and melatonin, a hormone secreted at night.
Humans cannot produce L-tryptophan on their own. So it has to be gotten from food (or supplements). In one experiment, depriving insomniacs of L-tryptophan made their insomnia worse, as recorded by studies conducted in a sleep lab. Low levels of tryptophan resulted in sleep that was lighter and less continuous. This suggests that something about L-tryptophan facilitates sleep.
Laboratory tests show that tryptophan administered at night increases concentrations of both serotonin and melatonin in the brain. So its sedative effects are probably due to its enhancement of the melatonin or the serotonin system.
Randomized Controlled Trials
Taken at bedtime in amounts of 1 to 4 grams, L-tryptophan has been found to be at least somewhat effective for people with insomnia in several studies, including double-blind trials. But results from three randomized controlled trials, considered the highest standard of evidence, are mixed.
- In an early study of 96 “serious insomniacs,” weeklong treatment with tryptophan was compared with weeklong use of a placebo. No differences were noted during the tryptophan treatment—but participants taking tryptophan reported falling asleep more quickly than normal in the week following treatment.
- In a subsequent study, people with severe chronic insomnia were divided into two groups: one group took tryptophan nightly for 4 weeks, followed by 4 weeks of placebo; the other began with placebo and after 4 weeks swtiched to tryptophan. Group A reported improved sleep quality while taking the tryptophan; group B did not.
- In a more recent study, tryptophan from squash seeds and pharmaceutical-grade tryptophan, both in the form of food bars, significantly improved sleep duration and sleep quality in study participants compared with a food bar containing carbohydrate alone. The tryptophan from squash seeds outperformed the pharmaceutical-grade tryptophan in reducing time awake at night.
Well yes, these results are underwhelming.
Consider This, Too
Other research is more encouraging. L-tryptophan in some studies has reduced participants’ sleep latency and cut down on nighttime wake-ups. Reviewers make these comments:
- The best results seem to occur in cases of mild insomnia with long sleep latency.
- People with more severe forms of insomnia may need to take L-tryptophan for several nights before they notice improvement in their sleep.
- In people with sleep maintenance insomnia, L-tryptophan may be more effective for those who wake up several times a night rather than for those who awaken less frequently.
Foods High in Tryptophan
As alternative treatments for insomnia go, L-tryptophan supplements are now considered safe and relatively free of side effects. (For pregnant and breast-feeding women, however, L-tryptophan is listed as “likely unsafe.”)
But you may be able to get most of what you need in your daily diet. Meat, fish, and seafood contain lots of of L-tryptophan; eggs, cheese, and milk contain quite a bit, too. The following foods are also high in L-tryptophan:
- soybeans and soy products
- sesame seeds
- mushrooms, wild and garden variety
- turnip and mustard greens
One last caveat. By itself, L-tryptophan does not cross the blood-brain barrier. Combining an L-tryptophan-rich food with a carbohydrate greatly improves L-tryptophan uptake in the brain. So for your evening snack, have your cheese on a cracker and your tofu with rice.
If you’ve tried L-tryptophan supplements, what effect did they have on your sleep?