STOCKHOLM, June 2 ― Junk food is already known to impact cardiovascular health, diabetes and the skin, but could it also be harmful to sleep? So suggests a new study conducted by researchers in Sweden, who found that the quality of deep slow-wave sleep, considered the most restorative, could be disrupted after eating unhealthy foods.
This is not the first time that scientists have investigated how what we eat can be associated with changes in our sleep. It has been shown, for example, that a high-sugar diet can influence sleep quality. However, little research has looked at how a particular diet directly affects this essential moment of rest and recuperation. And that's what researchers at Uppsala University set out to investigate. “Both poor diet and poor sleep increase the risk of several public health conditions. As what we eat is so important for our health, we thought it would be interesting to investigate whether some of the health effects of different diets could involve changes to our sleep,” says Jonathan Cedernaes, Physician and Associate Professor in Medical Cell Biology at Uppsala University.
Impacting sleep's restorative properties
The researchers gave participants a healthy and then a less healthy diet in random order. While both diets consisted of the same number of calories, one contained higher amounts of saturated fats, processed foods and sugar ― in other words, junk food ― while the other consisted mainly of foods considered healthy. Each diet was followed for a week, with sleep, activity and meal schedules monitored individually. As a final step, participants were monitored in a sleep laboratory at the end of each diet, in order to measure their brain activity in several phases: a normal night, in a state of wakefulness, then in “catch-up” mode for lost sleep.
Published in the journal Obesity, this research revealed that junk food didn't necessarily affect sleep duration ― participants slept the same number of hours regardless of diet ― or the time spent in the different stages of sleep, but it did play a role in the quality of deep sleep, and consequently its restorative properties. “Specifically, we looked at slow-wave activity, a measure that can reflect how restorative deep sleep is. Intriguingly, we saw that deep sleep exhibited less slow-wave activity when the participants had eaten junk food, compared with consumption of healthier food,” explains Jonathan Cedernaes in a news release.
Some limitations
However, the scientists were unable to determine the long-term impact of junk food on sleep. It should also be noted that this study only included 15 people, a very small sample due to the need to monitor them for several days in a sleep laboratory. The researchers point out that further work is now needed to find out more, if not in greater detail, about the role played by unhealthy diets on other sleep-related functions. “It would also be interesting to conduct functional tests, for example to see whether memory function can be affected. This is regulated to a large extent by sleep. And it would be equally interesting to understand how long-lasting the observed effects may be,” says Jonathan Cedernaes.
Finally, the scientists also plan to investigate the substance implicated in sleep disruption, be it sugar, saturated fat, processed foods, or all of them at once. This is a point they will explore in further research. ― ETX Studio
