Originally published in The Globe and Mail, May 25, 2018
Mounting evidence suggests that what you eat – and what you don’t eat – affects the time it takes to fall asleep when you go to bed and the amount of time you spend in deep, restorative sleep. (Restorative sleep revitalizes biological processes that keep the body and mind healthy and properly functioning.)
A 2016 controlled study carried out at Columbia University in New York, for example, found that eating too much saturated (animal) fat and too little fibre was tied to lighter, less restorative sleep. And, consuming too much added sugar was linked to waking up more often during the night.
Research suggests that diet can impact hormones that regulate sleep duration and sleep quality. For instance, foods can influence the secretion of melatonin, a brain chemical that controls the body’s internal clock to regulate sleep.
Certain foods deliver melatonin naturally, while others contain nutrients, such as B vitamins and tryptophan (an amino acid), that are used to synthesize melatonin in the brain. And some foods increase the production of prostaglandins, hormone-like compounds that promote sleep.
It’s recommended that adults get seven to nine hours of sleep each night; children and teenagers, depending on age, should get 10 to 13 hours.
Too little sleep is thought to increase the risk of overweight and obesity, type 2 diabetes and cardiovascular disease. Getting less than six hours of sleep a night for four or more consecutive days has been shown to impair cognitive performance and mood, blood-sugar regulation, appetite control and immune function.
While studies have been small and of short duration, findings suggest that the following foods (and beverages) can help improve the duration and quality of your sleep. Even better, they’re part of an all-round healthy diet that protects against high blood pressure, heart disease, type 2 diabetes, cognitive decline and cancer.
Tart cherry juice. Made from sour cherries (not the sweet, black cherries of summer), tart cherry juice is one the best natural food sources of sleep-promoting melatonin.
Research conducted in healthy volunteers found that, compared to a placebo beverage, drinking two tablespoons of tart cherry juice concentrate diluted in water twice daily for one-week increased melatonin in the body and improved sleep duration and quality. Tart cherry juice has also been shown to improve sleep among older adults with insomnia.
Also eat: Pistachios, eggs, fish, black rice, red rice, lentil sprouts.
Yogurt. This dairy product is an excellent source of tryptophan, an amino acid that’s needed to synthesize the sleep-regulating brain chemical serotonin. Serotonin is also thought to increase the secretion of the sleep-hormone melatonin.
Research has found that increased dietary tryptophan intake in the evening is associated with improved sleep quality and enhanced alertness in the morning in adults with sleep disturbances, presumably as a result of better sleep.
Also eat: Milk, turkey, hemp seeds, eggs, Parmesan cheese, edamame, tofu, kidney beans, lima beans, tuna, pumpkin seeds.
Salmon. Eating fish at least once a week has been shown to improve sleep in children and adults. (Interestingly, improving sleep is thought to be one way in which eating fish increases memory and learning.)
Omega-3 fatty acids in oily fish, one in particular called DHA (docosahexaenoic acid), has been shown to help regulate the production of sleep-inducing prostaglandins and melatonin.
Vitamin D in fatty fish is also thought to aid sleep. (Six ounces of cooked Atlantic salmon supplies 890 international units of vitamin D; most Canadians are advised to consume 1000 IU daily.)
Fish is also a good source of vitamin B6, a nutrient needed to convert tryptophan to melatonin.
Also eat: Sardines, anchovies, Arctic char, trout, tuna, herring and mackerel.
Kiwi fruit. A 2011 study found that adults with sleep problems who ate two medium-sized kiwi fruits before bedtime for two months experienced significant improvements in sleep – they fell asleep more quickly and slept more soundly.
Kiwi is a good source of serotonin, which helps initiate and maintain sleep. It’s also thought that antioxidants in kiwi, such as vitamins C and E, play a role in the fruit’s sleep-promoting properties.
Also eat: Pineapple, banana, plums, tomatoes, plantain, spinach, walnuts.
Sleep is a required refresh for your brain.