Can food ever really help you sleep?
Sleep deprivation is a global epidemic with scary implications for human wellbeing.
For those who find it hard to get to sleep, could a solution lie on our dinner plates? And are bananas really ‘sleeping pills in a peel’, as one headline has claimed? Sue Quinn investigates
If a good night‘s sleep is just a dream for you, welcome to the growing ranks of the bleary-eyed club. According to one survey, more than 60 per cent of Britons are unhappy with the amount of shuteye they’re getting.
The latest research has linked sleep deprivation to everything from obesity to cancer, while Rand Corporation, the global think-tank, estimates lack of sleep among UK workers is costing the economy £40 billion a year. But is there any truth in the idea that (as well as getting to bed earlier) we can solve the problem by eating certain foods before we hit the sack?
Sleep and diet – is there a link?
Time was when a mug of hot milk at bedtime was a widely touted dietary route to a deep and delicious sleep. But over the past decade a variety of foods have been hailed as potential insomnia cures.
Bananas, for example, have been called ‘practically a sleeping pill in a peel’ according to one newspaper report. And online, foods as varied as jasmine rice, yogurt, sweet potato and kale are claimed to cure nocturnal tossing and turning. But, as ever, nothing’s that simple.
''Emerging evidence suggests there is a link between diet and sleep''
Emerging evidence suggests there is a link between diet and sleep, but the associations are complex and the research is scarce, according to sleep specialists. “It’s the hormone melatonin that regulates our sleep patterns,” explains Dr Renata Riha, a consultant in sleep and respiratory medicine at the University of Edinburgh.
Melatonin is synthesised from serotonin, a neurotransmitter that also helps regulate mood and feelings of calm. Tryptophan, an amino acid, is a building block of both serotonin and melatonin and its metabolism is still not fully understood. It is known, however, that the body can’t produce tryptophan on its own, so we need to consume it.
The jury’s still out
“The link between diet and sleep is complex, varies from individual to individual and is very poorly studied,” according to Dr Riha. She says there’s no proof that particular foods can cure insomnia or improve the quality or quantity of our sleep, despite widespread claims online and in the media.
“Most of the studies are short-term and they haven’t controlled the timing of the food intake as well as they might,” she says. So bananas aren’t sleeping pills in fruit form? “There’s no evidence to state this,” she says.
In short, no single food has been proven to contain sufficient tryptophan and/or melatonin to make us drowsy – not even cow’s milk, reputed to be the most soporific food of all. A 2012 study into diet and sleep by the University of Helsinki found that even a large daily serving of regular cow’s milk before bed had no effect on sleep. It could be that the comforting routine of a milky drink before bed, and consuming it warm, accounts for its soporific reputation.
Interestingly, however, milk from cows milked at night, which contains more tryptophan and melatonin than standard milk, ‘significantly’ improved the sleep of participants in a trial.
A handful of small studies suggest that certain foods work for some people, according to Dr Alanna Hare, consultant in respiratory and sleep medicine at the Royal Brompton Hospital. These include protein-rich foods such as milk and dairy, nuts, eggs, meat, turkey, beans and chickpeas (which contain high levels of tryptophan) and walnuts and sour cherries (dried and in juice form), which are rich in melatonin.
“There is some literature that suggests consuming foodstuffs high in tryptophan or melatonin may increase sleep duration and quality,” Dr Hare says. She advises consuming these sorts of foods with carbohydrates to make the tryptophan and/or melatonin more readily available to the brain. An example of this would be peanut butter on toast, or cheese and crackers, eaten as a bedtime snack.
Dr Hare stresses, however, that there’s limited clinical evidence that eating these foods will improve your slumber. “Overall, the extent to which diet and nutrients can boost sleep remains unclear,” she concludes. “Traditional sleep-promoting foods are backed by only limited clinical evidence, although they may be useful in some cases.”
Deficiencies may play a role
Food might play a more significant role in improving sleep patterns if you’re deficient in B vitamins or magnesium, as these nutrients influence the secretion of the sleep hormone melatonin, explains Dr Hare. This may account for the banana’s reputation as a ‘sleeping pill’ as the fruit is a good source of magnesium and B vitamins, as well as tryptophan.
''B vitamins or magnesium [...] these nutrients influence the secretion of the sleep hormone melatonin''
“There is evidence of a modest influence of group B vitamins and magnesium supplementation on sleep quality, rather than on sleep duration,” Dr Hare says. “But this may only be relevant for people who are deficient in these substances.“
If you do sleep poorly, Dr Hare says it might be worth boosting your intake of foods containing high levels of these nutrients. Magnesium-rich foods include dark leafy greens, nuts such as almonds, seeds, fish, beans and wholegrains. Foods high in B vitamins include milk, eggs, fortified breakfast cereals, rice and wholegrains.
The bottom line
There’s scant evidence that eating particular foods will cure your insomnia but sleep experts say foods rich in melatonin or tryptophan might be worth trying if your sleep is patchy. But they say it’s better to eat a balanced and varied diet rich in fresh fruit, vegetables, wholegrains and low-fat protein sources.
All these foods contain plenty of tryptophan, as well as group B vitamins, minerals and unrefined carbohydrates that can improve sleep. “Until further studies are conducted, this is the best means to address the issue
of improving sleep through diet,” concludes Dr Hare.
True or False?
Bananas are “a sleeping pill in peel form”: FALSE
Some foods rich in tryptophan or melatonin might improve some people’s sleep, although the evidence is limited: TRUE
Deficiencies in magnesium and B group vitamins are linked to poor sleep: TRUE
Camomile tea is proven to improve sleep: FALSE