New study: Popular fruit helps improve sleep

(Dan Tri) - A study recently published in the journal Food & Function shows that walnuts rich in tryptophan and melatonin can help improve sleep quality.

Walnuts and the mechanism of their effects on sleep

Walnuts help people with insomnia and improve sleep quality (Photo: Unsplash).

Walnuts contain tryptophan – an amino acid needed by the body to produce melatonin, a hormone that regulates sleep-wake cycles. In addition, this nut also provides plant-based melatonin, which helps increase melatonin levels in the body after eating.

Scientists conducted an 18-week study with 76 adults (20-35 years old). In the first phase, they ate 40 grams of walnuts every day for 8 weeks.

Participants then stopped eating nuts and continued on their Mediterranean diet, while also adhering to sleep recommendations such as avoiding caffeine, limiting evening electronic screens, and keeping a regular sleep schedule.

Participants wore sleep trackers and provided urine samples for testing. The results: Faster, better-quality sleep.

After 8 weeks of eating walnuts, the study participants showed a significant reduction in the time it took them to fall asleep. The ratio of actual sleep time to total time spent in bed increased by 0.7%. At the same time, urine tests also recorded increased evening melatonin levels, reflecting a significant improvement in sleep quality.

Participants also reported being more alert during the day – a sign of quality sleep.

According to the research team, 40 grams of walnuts per day provides about 84.6 mg of tryptophan and 118 mg of melatonin, enough to help the body produce natural melatonin.

Limitations to note

About 40 grams of walnuts a day can help you sleep better (Photo: Unsplash).

The study did not standardize the participants’ entire diets, nor did it account for tryptophan and melatonin intake from other sources. Therefore, more evidence is needed before any long-term effects can be definitively determined.

Experts recommend: if you often have trouble sleeping, a small handful of walnuts every day can be a simple choice, but it should be combined with healthy sleeping habits such as going to bed on time and avoiding electronic devices before bed.

Many other benefits of walnuts

In addition to its effects on sleep, walnuts are also proven to be good for brain and cardiovascular health:

Brain: A 2020 study in PMC noted that a walnut-rich diet increased antioxidant capacity and protected nerve cells, especially in a mouse model of Alzheimer's.

Mental: Eating walnuts for breakfast improves cognitive performance, supports dopamine activity, and reduces stress.

Heart: Analysis on ScienceDirect (2024) shows that walnut supplementation helps reduce bad cholesterol without causing weight gain.

Intestinal tract: Fiber and polyphenols in walnuts nourish the gut microflora, supporting weight and blood sugar control, especially in type 2 diabetics.

Additionally, these nuts are rich in omega-3s, fiber, and antioxidants, which help reduce the risk of heart disease and support brain function.

How much is enough?

Nutritionists recommend eating only about 40 grams per day. Eating too much (over 50-100 grams per day) can cause bloating, constipation, diarrhea, and even weight gain due to the high calories and fat content. People with irritable bowel syndrome need to be especially careful.

Source: https://dantri.com.vn/suc-khoe/nghien-cuu-moi-loai-qua-pho-bien-giup-cai-thien-giac-ngu-20250914011232140.htm