In a new study, researchers at Uppsala University have investigated how junk food affects sleep. In a randomized order, healthy volunteers consumed an unhealthy and a healthier diet. When compared to those who followed the healthier diet, the participants’ deep sleep quality deteriorated after the unhealthier diet. The findings have been published in the journal
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. However, few studies have looked into how nutrition impacts sleep directly. One method is to have the same individual take various diets in a randomized order.
“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. In this context, so-called intervention studies have so far been lacking; studies designed to allow the mechanistic effect of different diets on sleep to be isolated,” said Jonathan Cedernaes, Physician and Associate Professor in Medical Cell Biology, Uppsala University.
Junk Food Hampers Deep Sleep Quality
Previous epidemiological studies have shown that diets with greater sugar content, for example, are linked to poorer sleep. Yet sleep is an interplay of different physiological states, as Cedernaes explains:
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“For example, deep sleep can be affected by what we eat. But no study had previously investigated what happens if we consume an unhealthy diet and then compared it to the quality of sleep after that same person follows a healthy diet. What is exciting in this context is that sleep is very dynamic. Our sleep consists of different stages with different functions, such as deep sleep which regulates hormonal release, for example. Furthermore, each sleep stage is hallmarked by different types of electrical activity in the brain. This regulates aspects such as how restorative sleep is, and differs across different brain regions. But the depth or integrity of the sleep stages can also be negatively affected by factors such as insomnia and aging. Previously, it has not been investigated whether similar changes in our sleep stages can occur after exposure to different diets.”
Each study session included several days of sleep laboratory monitoring. As a result, the study only involved 15 people. In total, 15 healthy, normal-weight young males took part in two sessions.
Participants were first examined for factors such as their sleep patterns, which had to be normal and within the recommended range (seven to nine hours of sleep each night on average).
The individuals were randomly assigned to either a healthier or an unhealthier diet. The two diets had the same number of calories, which were tailored to each person’s daily needs.
The unhealthy diet had a greater sugar and saturated fat content, as well as more processed food products. Each diet’s meals required to be consumed at times that were uniquely tailored and matched across the two dietary conditions.
Each diet was followed for a week while the individuals’ sleep, activity, and food patterns were tracked on an individual basis.
The subjects were tested in a sleep laboratory following each diet. They were first permitted to sleep normally for one night while their brain activity was monitored. After that, the individuals were kept awake in the sleep laboratory before being permitted to sleep again. Their sleep was also recorded in this case.
Deep Sleep Slow-Wave Quality: Healthy vs Unhealthy Food
“What we saw was that the participants slept for the same amount of time when they consumed the two diets. This was the case both while they were following the diets, as well as after they had switched to another, identical diet. In addition, across the two diets, the participants spent the same amount of time in the different sleep stages. But we were particularly interested in investigating the properties of their deep sleep. 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 the consumption of healthier food. This effect also lasted into a second night, once we had switched the participants to an identical diet. Essentially, the unhealthy diet resulted in shallower deep sleep. Of note, similar changes in sleep occur with aging and in conditions such as insomnia. It can be hypothesized, from a sleep perspective, that greater importance should potentially be attached to diet in such conditions,” explains Cedernaes.
The researchers do not yet know how long the sleep consequences of an unhealthy diet may last. The study did not look at whether shallower deep sleep might affect functions governed by deep sleep, for example.
“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. Currently, we do not know which substances in the unhealthier diet worsened the depth of deep sleep. As in our case, unhealthy diets often contain both higher proportions of saturated fat and sugar and a lower proportion of dietary fiber. It would be interesting to investigate whether there is a particular molecular factor that plays a greater role. Our dietary intervention was also quite short, and both the sugar and fat content could have been higher. It is possible that an even unhealthier diet would have had more pronounced effects on sleep,” notes Cedernaes.
Reference :
- Exposure to a more unhealthy diet impacts sleep microstructure during normal sleep and recovery sleep: A randomized trial – (https:pubmed.ncbi.nlm.nih.gov/37245331/)
Source: Medindia
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