Young Adults Consuming Walnuts Reported Improved Sleep Quality, New Study Finds
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 randomised 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 randomised 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 just one in five of Britons getting a full eight hours or more of sleep a 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:
Prawn, Barley & Walnut Jambalaya
Ingredients
- 100 g pearl barley
- 50 g wholegrain rice
- 1 tbsp rapeseed oil
- 1 onion chopped
- 1 red pepper diced
- 250 g sweet potatoes cut into 1 cm dice
- 1 tbsp Cajun seasoning
- 400 g can chopped tomatoes
- 75 g California Walnuts roughly chopped
- 165 g pack raw king prawns
- ½ x 25g parsley chopped
Instructions
- Cook the barley in a large saucepan of boiling water for 15 minutes, then add the rice and cook for a further 25 minutes until tender, drain and rinse.
- Meanwhile, heat the oil in a large frying pan and fry the onion, pepper and sweet potatoes for 5 minutes, stir in the Cajun seasoning and cook for a minute. Add the chopped tomatoes with ½ can water and the Walnuts, cook for 5 minutes.
- Stir in the barley mix and prawns and cook for a further 5 minutes until the prawns are pink and cooked through, then sprinkle in the parsley to serve.
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Walnut Mince Chilli
Ingredients
- 100 g California Walnuts
- 300 g mushrooms
- 1 tbsp oil
- 2 cloves garlic crushed
- 1 tsp ground cumin
- 1 tsp chilli powder
- 400 g can chopped tomatoes
- 2 tbsp tomato puree
- 400 g can red kidney beans drained and rinsed
- 400 g can black beans drained and rinsed
- 2 tbsp chopped coriander
Instructions
- Place the walnuts in a food processor and mix to give a coarse crumb. Repeat with the mushrooms and mix into the walnuts.
- Heat the oil in a large saucepan and fry the walnut mixture and garlic for 5 minutes. Add the spices and cook for 1 minute. Stir in the tomatoes, tomato puree and both beans and cook gently for 10 minutes, stirring occasionally. Season and stir in the coriander.
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Great to freeze in portions.
CHILLI 5 WAYS: serve with cooked long grain rice; spoon over a halved baked potato; mix with pasta and top with grated Cheddar and bake; serve on top of tortilla chips with guacamole, soured cream and melted cheese; and finally, serve in a tortilla wrap with cooked rice and sliced avocado for a quick burrito.
Walnut & Kale Pasta
Ingredients
- 200 g California Walnuts
- 250 g bag kale thick stalks removed
- 350 g wholewheat pasta
- 300 g pack silken tofu
- 25 g pack basil leaves picked
- 3 tbsp extra virgin olive oil
- 1 clove garlic sliced
Instructions
- Place 150g Walnuts in a bowl and cover with just boiled water, set aside for 15 minutes then drain.
- Meanwhile, cook the kale in a large saucepan of boiling water for 2 minutes, remove with a slotted spoon to a colander and run under cold water, then drain well.
- Add the pasta to the kale water and cook for 11-13 minutes until tender, drain well, reserving a mug of cooking water and return to the pan.
- Place the kale in a food processor with the soaked Walnuts, tofu, ¾ basil leaves, olive oil and 100ml reserved pasta water, season and blitz to a smooth paste, adding a little more of the water if required. Stir into the pasta with most of the remaining Walnuts, roughly chopped.
- Serve sprinkled with the remaining basil leaves and Walnuts.
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Barbecue Chicken with Loaded Vegetables
Ingredients
- For the chicken:
- 3 tbsp tomato ketchup
- 2 tbsp brown sauce
- 1 tsp Worcestershire sauce
- 2 tbsp clear honey
- 1 tbsp barbecue seasoning
- 1 tbsp olive oil
- 25 g California Walnuts finely chopped
- 4 chicken breast fillets flesh scored
- For the vegetables:
- 300 g broccoli cut into small florets
- 100 g frozen edamame beans
- 1 tbsp olive oil
- 400 g can borlotti beans drained and rinsed
- 100 g California Walnuts roughly chopped
- 195 g can sweetcorn drained
Instructions
- Mix all the marinade ingredients together and add the chicken, ensuring it’s completed coated. Marinate ideally for 1-2 hours.
- Preheat the oven to 200oC, gas mark 6. Place the chicken on a baking tray, reserving the excess marinade and roast for 25-30 minutes.
- Meanwhile, blanch the broccoli and edamame beans in boiling water for 2-3 minutes and drain well. Heat the oil in a large frying pan and fry the broccoli mix, borlotti beans, Walnuts and sweetcorn with the remaining marinade and juices from the chicken, for 3-4 minutes.
- Slice the chicken and serve with the vegetables.
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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
- https://yougov.co.uk/health/articles/27245-three-quarters-brits-get-less-eight-hours-sleep
- 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.
