New review identifies pistachios as a promising whole food for sleep research

Nearly one-third of U.S. adults report sleeping less than seven hours a night, below the minimum amount recommended for most adults, while nearly one in five has trouble staying asleep most days or every day. At the same time, nearly one-third of Americans say they are seeking improved sleep from foods, beverages or nutrients. 

Pistachios have attracted researchers' attention because they naturally bring together several nutrients and plant compounds connected to sleep. Now, a new narrative review published in Nutrition Research Reviews identifies pistachios as a promising whole food for sleep research and explores how their nutrient profile may influence processes related to sleep quality, falling asleep, staying asleep and regulation of the sleep–wake cycle. 

Three reasons pistachios are intriguing to sleep researchers and clinicians: 

• Supporting the body's production of melatonin: Pistachios provide tryptophan, vitamin B6 and magnesium, which the body uses in the production of serotonin and melatonin. Serotonin is involved in sleep regulation and is also used to make melatonin, the hormone that helps regulate the sleep–wake cycle. Pistachios also contain phytomelatonin, the form of melatonin produced by plants, although its absorption and effects from eating pistachios have not been established in people. 

• Supporting calming signals in the brain: Pistachios provide vitamin B6 and magnesium, which are involved in the production and function of gamma-aminobutyric acid (GABA), a brain chemical that helps quiet nerve activity and plays a role in regulating sleep.

• Connecting the gut and sleep: Pistachios provide fiber and polyphenols that gut microbes can break down into compounds that may influence communication between the gut and brain, including signaling involved in sleep regulation. Researchers are exploring whether these interactions could be another way pistachios influence sleep. 

How much tryptophan do pistachios provide?  

A one-ounce serving of pistachios provides about 71 milligrams of tryptophan, roughly 20% of the daily amount recommended for a 154-pound adult. Tryptophan is an essential amino acid the body uses to make serotonin, a brain chemical involved in sleep regulation, and melatonin, the hormone that helps regulate the sleep–wake cycle. 

Pistachios also provide vitamin B6 and magnesium, which help the body convert tryptophan along the pathway to serotonin and melatonin. Together, this combination is one reason researchers are interested in studying whole pistachios and sleep. 

Why the whole pistachio matters 

Most nutrition-and-sleep research has examined individual nutrients, extracts or supplements. Pistachios bring several of these components together naturally in one food, creating an opportunity to study how they may work together rather than in isolation. This natural structure, how nutrients and plant compounds are packaged together and interact within a food, is known as the food matrix, and in this context – the pistachio food matrix.

Pistachios are compelling for sleep research because they bring together several nutrients and plant compounds connected to sleep physiology within one whole food. Rather than focusing on a single 'sleep nutrient,' this review provides a rationale for studying how the complete pistachio food matrix may affect sleep-related pathways." 

Marie-Pierre St-Onge, PhD, the review's senior and corresponding author and director, Center of Excellence for Sleep and Circadian Research, Columbia University Irving Medical Center

As part of the review, researchers assessed laboratory studies that simulated digestion and fermentation of pistachios to explore how the pistachio food matrix may also influence how and when pistachio components become available to the body. Findings demonstrated that gut microbes can ferment pistachio fiber, transform its polyphenols and contribute to a longer release of phytomelatonin from pistachios. 

These findings suggest that researchers should study whole pistachios rather than nutrients or supplements in isolation, because nutrients may behave differently when consumed as part of the pistachio food matrix. 

Do pistachios improve sleep? 

The authors of this review concluded that pistachios could represent a promising wholefood intervention for improving sleep due to their unique combination of nutrients and bioactives, and map a clear path to additional research needed. 

The authors call for randomized controlled trials examining whole-pistachio consumption, dose–response relationships, melatonin levels, sleep outcomes and the bioavailability of key compounds. They also recommend investigating whether pistachio variety, growing conditions and processing influence the nutrient and bioactive content of pistachios. 

 "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," explains Dr. St-Onge. 

That next phase of research is already underway. American Pistachio Growers is supporting several university-led human clinical studies examining pistachios and sleep. Results are not yet available, but the studies represent an important next step from biological rationale to direct human evidence.