Posts Tagged “walnut consumption”
Folsom, CA — California Walnut Commission: Eating a daily serving of about one handful of walnuts (40 grams or about 1.5 ounces) with dinner may help improve measures of overall sleep quality and reduce daytime sleepiness in healthy young adults, according to a new randomized controlled trial published in Food & Function.[1]*
Researchers from the University of Barcelona aimed to study the potential impact that daily walnut consumption could have on specified urine biomarkers (6-SMT, a biproduct of melatonin), sleep quality parameters (sleep latency, wake after sleep onset, awakenings, and efficiency) and daytime sleepiness.
The study evaluated the effects of consuming 40 grams of walnuts daily with dinner over an eight-week period among 76 healthy young adults ages 20-28 (85% female), who completed both walnut and control phases in a crossover design.
Researchers found that eating walnuts boosted a key biomarker of the sleep-regulating hormone, melatonin, which was significantly increased in evening urine samples after a four-week intervention period when participants consumed walnuts, as compared to the control period.
The walnut intervention also shortened the time it took participants to fall asleep by 1.3 minutes, improved overall sleep quality scores, and reduced 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. With these findings, the researchers suggest that walnut consumption could potentially be a simple, food-based approach to supporting healthy sleep.
“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,” said 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,[2] our results open the door to future research in other age groups and in people with sleep disorders.”
Insufficient sleep is seen as a global health concern, with multi-faceted public health implications, ranging from chronic illness to cognitive and economic impacts.[3]
The researchers explain that walnuts’ 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 vitamin B5 and vitamin B6) may help explain the positive outcomes seen in the study. These findings suggest walnuts may help naturally support sleep quality, though more research is needed to understand the mechanism.
Dr. María Fernanda Zerón-Rugerio, co-leader of the study explains, “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.”
This study is among the first to demonstrate walnuts’ potential as a sleep-supporting food. As such, the study contained a number of limitations, including unmeasured dietary tryptophan and melatonin intake, that restrict the applicability of the study findings to the general population. While further research is warranted to examine these effects, these initial findings add to the growing body of evidence supporting the role of diet and specific nutrient-dense foods, such as walnuts, in promoting sleep health.
Here are some easy ways to add a handful of walnuts to your evening meal:
- Enjoy a dinnertime staple like meatballs, and serve them with a flavorful, satisfying twist with these Greek Walnut Meatballs with Tzatziki Sauce.
- California Walnut Chili made with beans, veggies, and walnuts contains a combination of fiber, plant-based protein and good fats – a trio that can help keep blood sugar steady through the night, preventing 2 AM hunger wake-ups.
- Sprinkle chopped walnuts over oatmeal, salads, or roasted vegetables for a boost of texture, flavor, and nutrition.
- Blend walnuts into smoothies, stir them into yogurt, or use them as a crust for chicken or fish for an easy upgrade to everyday meals.
To learn more about the breadth of research supporting walnut consumption, along with recipe ideas and inspiration, visit walnuts.org.
About the California Walnut Commission
The California Walnut Commission (CWC) represents more than 3,700 California walnut growers and nearly 70 handlers, grown in multi-generational farmers’ family orchards. California walnuts, known for their excellent nutritional value and quality, are shipped around the world all year long, with more than 99% of the walnuts grown in the United States being from California. The CWC, established in 1987, promotes usage of walnuts through domestic and export market development activities as well as supports health research with consuming walnuts.
References:
*This research was funded by the California Walnut Commission. The funder made no contribution during the design or implementation of the study, nor in the interpretation of findings or the decision to publish.
- Zerón-Rugerio MF, Ibarra-Picón A, Diez-Hernández M et al. Daily Walnut Consumption Increases 6-Sulfatoxymelatonin Urinary Levels and Can Improve Sleep Quality: A Randomized Crossover Trial [published online ahead of print August 12, 2025]. Food & Function. DOI: 10.1039/d5fo00971e
- CDC Behavioral Risk Factor Surveillance System (BRFSS), 2013–2022. Sleep is not assessed on the core survey in the following years: 2015, 2017, 2019, and 2021. Percentage of adults not getting enough sleep, adjusted for age.
- Chattu VK, Manzar MD, Kumary S, Burman D, Spence DW, Pandi-Perumal SR. The global problem of insufficient sleep and its serious public health implications. Healthcare (Basel). 2019;7(1):1. doi:10.3390/healthcare7010001.
In a study from Indiana University Bloomington School of Public Health, funded by the California Walnut Commission, researchers show that adolescents and young adults who consumed walnuts with other nuts (WON) had the lowest prevalence of obesity.
Researchers analyzed data from the National Health and Nutrition Examination Survey (NHANES), including 8874 adolescents aged 12 to 19 years old and 10,323 young adults aged 20 to 39. The research focused on understanding the associations between consumption of walnuts and other nuts with measures of obesity including relative fat mass (RFM), a tool that estimates body fat percent and regional fat composition.
The study showed that, especially in adolescent girls and young women, the consumption of WON has the strongest inverse association with measures of obesity when compared to non-nut consumers. This association was not found among young men, adolescent boys, or adolescent girls who consumed walnuts only.
A systematic review of cohort studies indicated that long-term moderate intake of nuts (i.e., 1–2 servings of nuts per week) was associated with less weight gain and reduced risk of overweight/obesity and that consumption of a high-quality diet is inversely associated with body mass index, and even though walnuts and other nuts are energy dense, they may not promote obesity.
Scientists also make the distinction that these observations might be due to revere causality since “that people with obesity have altered their diets in terms of nut consumption to prevent more weight gain.”
Higher walnut consumption may be associated with a lower risk of death and an increase in life expectancy among older adults in the U.S., compared to those who do not consume walnuts.
A new study conducted Harvard T.H. Chan School of Public Health researchers, has been supported by the California Walnut Commission.
“What we’ve learned from this study is that even a few handfuls of walnuts per week may help promote longevity, especially among those whose diet quality isn’t great to begin with,” Yanping Li, Senior Research Scientist at the Department of Nutrition at Harvard T.H. Chan School of Public Health, and lead investigator of this research.
“It’s a practical tip that can be feasible for a number of people who are looking to improve their health, which is top of mind for many people,” Li said.
This study found five or more one-ounce servings of walnuts per week may provide the greatest benefit for mortality risk and life expectancy.
Eating five or more servings per week was associated with a 14% lower risk of death (from any cause), a 25% lower risk of dying from cardiovascular diseases, and a gain in about 1.3 years of life expectancy, compared to those who didn’t consume walnuts.
Consuming walnuts two to four times per week could have its benefits, too, with the study finding a 13% lower risk of death overall, 14% lower risk of dying from cardiovascular diseases, and a gain in about one year of life, compared to non-walnut consumers.
Participants were relatively healthy when they joined the studies and were followed for about 20 years (1998-2018).
Dietary intake was assessed every 4 years in which participants reported on their overall dietary intake – including how often they consumed walnuts, other tree nuts, and peanuts – as well as lifestyle factors like exercise and smoking status.
Based on this data, the researchers were able to identify associations between walnut consumption at varying levels and different health indicators related to longevity.
As a prospective observational study, these results do not prove cause and effect, but they do shed light on how walnuts may support an overall healthy lifestyle that promotes longevity.
Participants who consumed greater amounts of walnuts tended to be more physically active, have a healthier diet, lower alcohol consumption, and take multivitamins.
All of these factors could influence life expectancy, however, the researchers adjusted for these aspects in their analysis. In addition, it’s important to note that this data was collected before the current Covid-19 pandemic.
One ounce of walnuts is a powerhouse of important nutrients for optimum health, including protein (4g), fiber (2g), a good source of magnesium (45mg) and an excellent source of the essential omega-3 ALA (2.5g).