Fact checked by Nick Blackmer
:max_bytes(150000):strip_icc():format(jpeg)/Health-GettyImages-1312794999-6b94c8f68ce64fb0b3d2cda6116fac1c.jpg "Walnuts in brown bowl on wooden table, closeup view. Healthy food")
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- Eating 40 grams of walnuts daily improved sleep quality in young adults.
- Walnuts have melatonin, which helps you fall asleep faster and stay asleep longer.
- Tryptophan in walnuts supports the production of serotonin and melatonin, which regulate sleep.
Eating walnuts before bed may improve your sleep. Their melatonin content can help you fall asleep faster.
How Did Researchers Study Walnuts and Sleep?
To examine the link between walnuts and sleep, researchers recruited 76 young adults aged 20-35 to participate in an 18-week trial.
In the first phase of the 2025 study, which lasted eight weeks, participants were divided into two groups. One group ate 40 grams of walnuts with dinner each day, while the other did not. Participants were instructed not to eat other types of nuts during this time.
After a two-week washout period, the groups switched: Those who had been eating walnuts stopped, and the other group began eating them.
Throughout the study, participants provided urine samples to measure melatonin production. For seven consecutive days in each phase, they also wore wrist trackers that monitored their sleep patterns, activity levels, skin temperature, and light exposure.
Finally, they were assessed using a global sleep quality score, which measured four aspects of nighttime rest:
- Sleep latency (the time it takes to fall asleep)
- Sleep efficiency (the time spent asleep as a percentage of the time in bed)
- Number of awakenings
- Amount of time spent awake after falling asleep
What Were the Benefits of Eating Walnuts?
During the walnut-eating phase, participants had significant increases in evening melatonin production, took less time to fall asleep, and scored higher on global sleep quality. They also reported less daytime sleepiness.
The study had some limitations. It was relatively small and funded by the California Walnut Commission, but the authors stated that the organization did not influence the study's design or data interpretation.
Because participants knew whether or not they were eating walnuts, their beliefs or behaviors may have been influenced. Additionally, all participants were instructed to eat a Mediterranean-style diet during the trial, so other foods could also have played a role in the sleep improvements.
Why Do They Help You Sleep Better?
Again, the study has some caveats. But if eating walnuts really does improve sleep, as the research suggests, it may be due to the nuts’ hormone content.
Researchers also analyzed the walnuts' levels of sleep-friendly compounds, finding notable results. Each serving of walnuts contained an average of 84.6 milligrams of tryptophan, 118 nanograms of melatonin, and a tryptophan-to-competing amino acid (CAA) ratio of 0.058.
Each of these factors is meaningful for better rest. Tryptophan is “the biochemical starting point” for the synthesis of serotonin and melatonin, both of which regulate sleep, behavioral sleep medicine psychologist Daniella Marchetti, PhD, DBSM, told Health.
As for melatonin itself, it’s known as the “sleep hormone” for a reason. “Melatonin rises in the evening to signal that it is nighttime, which helps you fall asleep. [Therefore], eating foods with melatonin can boost these signals to help the body prepare for sleep,” said Marchetti.
The ratio of tryptophan to CAA also plays an important role.
“If you have a lot of amino acids competing for space to get through the ‘doorway’ in the brain, tryptophan usually loses out to its competitors,” said Marchetti. “Having a high CAA ratio means that tryptophan has a better chance at crossing the blood-brain barrier.”
Should You Add Eating Walnuts to Your Sleep Routine?
There are plenty of good reasons to snack on walnuts—like supporting heart health and cognition.
Getting more sleep might be another reason to chow down on them. However, “these results are strong enough to indicate that walnuts are a sleep-promoting food, but they would not be considered an adequate substitute for insomnia treatment at this time,” said Marchetti.
If you do opt for walnuts in the evening, Marchetti recommended 30-40 grams (about a small handful) after dinner or as a bedtime snack. This timing gives your body time to have a rise in melatonin, which can take 2-3 hours after consumption.
