Pistachios contain several nutrients and plant compounds involved in sleep-related processes, including tryptophan, magnesium, vitamin B6, fiber and naturally occurring melatonin.
That makes them an interesting food for sleep researchers. But there is an important catch: Scientists have not yet shown in human trials that eating pistachios actually helps people sleep better.
A new narrative review published in Nutrition Research Reviews examined the existing evidence around pistachios and sleep. The review was funded in part by American Pistachio Growers, and senior author Marie-Pierre St-Onge is a member of the organization’s advisory board.
Rather than testing pistachios directly in people, the researchers looked at studies of individual nutrients, supplements, other foods and laboratory experiments.
“Pistachios are compelling for sleep research because they bring together several nutrients and plant compounds connected to sleep physiology within one whole food,” said St-Onge, director of the Center of Excellence for Sleep and Circadian Research at Columbia University Irving Medical Center.
One reason for the interest is tryptophan, an amino acid the body uses to make serotonin and melatonin. Pistachios also contain vitamin B6 and magnesium, which are involved in those same pathways.
They also contain phytomelatonin, the form of melatonin found in plants, along with fiber and polyphenols that may influence communication between the gut and brain.
But most of that evidence is indirect.
Some studies have linked individual nutrients such as magnesium or tryptophan with sleep, while others have tested supplements or different melatonin-containing foods. Some of the evidence also comes from animal or laboratory research.
That means researchers still do not know whether eating pistachios themselves improves sleep, how much someone would need to eat or whether timing matters.
The authors argue that pistachios are worth studying as a whole food because several potentially relevant nutrients are packaged together.
“Well-designed human trials can help us determine whether the unique combination of nutrients and bioactive compounds in the pistachio food matrix produces measurable changes in melatonin, sleep quality, sleep duration or other sleep outcomes,” St-Onge said.
Those studies are beginning. American Pistachio Growers is supporting university-led human trials examining pistachios and sleep, but results are not yet available.
For now, the evidence makes pistachios a promising research question, not a proven sleep aid.
The review was funded in part by American Pistachio Growers and the National Institutes of Health. Senior author Marie-Pierre St-Onge is on the advisory board of American Pistachio Growers and is the author of Eat Better, Sleep Better.