Melatonin-boosting walnuts aid sleep quality and daytime energy, study finds

Eating one handful of walnuts (40 grams or about 1.5 ounces) with dinner may help improve overall sleep quality, according to a new randomized controlled trial. The paper also supports its effectiveness in reducing daytime sleepiness in healthy young adults. 

Researchers from the University of Barcelona, Spain, investigated this phenomenon by studying the parameters of specified urine biomarkers (6-SMT, a byproduct of melatonin), sleep quality (sleep latency, wake after sleep onset, awakenings, and efficiency), and daytime tiredness.

The eight-week study involved 76 healthy young adults aged 20–28 (85% female), who completed walnut and control phases in a crossover design.

“This is the first randomized controlled trial to show that daily walnut consumption measurably improved objective sleep quality and increased melatonin levels during evening hours after an intervention period,” says Dr. Maria Izquierdo-Pulido, lead researcher of the study out of the University of Barcelona.

“With over one in three American adults not meeting the recommended amount of sleep per night, our results open the door to future research in other age groups and in people with sleep disorders.”

The researchers suggest their findings offer a potentially simple, food-based approach to promoting healthy sleep.

Walnuts boost melatonin

The study in Food & Function found that eating walnuts boosted a key biomarker of the sleep-regulating hormone, melatonin. This was significantly increased in participants’ evening urine samples after four weeks of consuming walnuts, as compared to the control period.

Consistent walnut consumption shortened the time it took participants to fall asleep by 1.3 minutes while improving overall sleep quality scores and reducing self-reported daytime sleepiness compared to a control, nut-free period.

While global sleep quality scores improved, there were no significant differences in measures of circadian-related variables between the intervention and control conditions.

Walnuts contain a unique combination of sleep-supportive nutrients such as tryptophan (84.6 mg) — a precursor to melatonin, plant-based melatonin (118 ng), magnesium (45 mg), and B vitamins (0.2 mg each of vitamin B5 and vitamin B6). The researchers say this may help explain the positive outcomes seen in the study.

However, more research is needed to understand the mechanism. Dr. María Fernanda Zerón-Rugerio, co-leader of the study, details: “While the observed effects in this study came following walnut consumption at dinner, we believe that the daily intake, rather than the timing, led to the sleep-supportive benefits.”

Natural sleep interventions

Insufficient sleep is seen as a global health concern, with multi-faceted public health implications, ranging from chronic illness to cognitive impacts. Natural solutions addressing these concerns are in the spotlight this year, including targeted postbiotics.

In this field, ADM offers its L. gasseri CP2305 postbiotic that supports aspects of women’s health as well as sleep. It has demonstrated benefits for women dealing with menopausal symptoms of emotional swings and sleep deprivation.

Meanwhile, a recent botanical study confirmed that RelaxPLX, a natural lemon verbena (Lippia citriodora) extract by Monteloeder, may support relaxation and sleep quality in teenagers experiencing occasional stress and restlessness.