Want a good night’s sleep tonight? Pile your plate with plenty of fibre and plants
Olga Pankova/Getty Images
Eating more fibre may help you sleep more deeply, while consuming a wider variety of fruits, vegetables and nuts could help you nod off faster. That’s according to the most comprehensive look yet at how what we eat throughout the day affects our sleep that night.
“Increasing fibre and plant variety is already recommended for overall health, carries low risk for most people and may offer sleep benefits as an additional upside,” says Hagai Rossman at the Weizmann Institute of Science in Israel.
Prior studies have linked eating fibre-rich, plant-based foods to better sleep, but these mostly relied on people recalling their diet in surveys, sometimes weeks or months later. In addition, when sleep has been objectively measured, it has typically been via movement trackers that cannot distinguish between its deeper and lighter phases, which is important for gauging sleep quality.
Now, Rossman and his colleagues have gained the clearest picture to date by analysing sleep and dietary data collected from more than 3500 adults, aged 53, on average. “Previous studies haven’t looked at so many dietary and sleep factors,” says Marie-Pierre St-Onge at Columbia University in New York City.
Over two consecutive days, each participant logged what they ate in a mobile app, either during its consumption or shortly afterwards. At night, they wore a device that has been approved by the US Food and Drug Administration to measure sleep. This is composed of sensors worn on the chest, a wrist and a finger that track snoring, blood oxygen levels, and heart and breathing rates.
The researchers used these measurements to estimate how long the participants spent in the various stages of slumber: light sleep (known as N1 and N2), the deep, restorative phase (N3) and rapid eye movement (REM) sleep, when dreams tend to be long and abstract.
Next, the researchers used a computational model to predict how 25 dietary factors affected sleep that night. They accounted for factors that could skew the results, including age, sex, caffeine intake and – most importantly – dietary and sleep data from the previous day. “Controlling for the previous day really allowed us to explore how what you eat in the day affects your next night of sleep,” says Rossman.
The researchers found that the participants who reported eating more fibre than the cohort’s average of 21 grams per day – equivalent to around 2.5 cups of peas – tended to get better sleep that night than those with a below-average fibre intake. For instance, the former group spent 3.4 per cent more time in N3 and 2.3 per cent less of it in light sleep. “They’re moving in a direction of more restorative sleep, which is important for a healthier brain and body,” says St-Onge.
It is unclear exactly why fibre has these effects, but studies suggest that gut microbes can ferment it into short-chain fatty acids, such as butyrate, that reduce inflammation and alter gut-to-brain signalling in a way that promotes deep sleep, says Rossman.
The researchers also found that those with an above-average fibre intake had a slightly lower heart rate during the night than those who consumed less. A low nocturnal heart rate suggests that a person has entered a state of deep rest and repair, which puts less strain on the heart. “A 1 beat-per-minute difference [as observed between the high- and low-fibre groups] might not be that important for one night, but if that difference is sustained over decades or a lifetime, that could make an important difference [for cardiovascular health],” says St-Onge.
Further analysis revealed that those who ate more than five types of plant-based foods a day also fell asleep slightly faster and had a lower heart rate during sleep than those who ate less. This could be because eating a broader mix of plants provides a range of vitamins, minerals and other molecules, like polyphenols, that help to reduce inflammation and shift the nervous system into a rest-and-digest mode, says Rossman.
Future trials, ideally in sleep clinics, that randomly assign people to eat different amounts of fibre and broader or narrower ranges of plant-based foods are needed to confirm the findings, says St-Onge.
Topics: