A new study by Uppsala University shows that junk food harms sleep. Healthy volunteers ate both unhealthy and healthy diets randomly. A poor diet leads to worse sleep quality than a healthy diet. They were published in the Obesity Journal.
Some studies link diet to sleep changes, but few examine how diet directly affects sleep. One method is to give participants various diets to observe the effects randomly.
Jonathan Cedernaes, Physician and Associate Professor in Medical Cell Biology at Uppsala University said, “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.”
Past studies show that sugary diets can lead to poorer sleep. Cedernaes notes that rest involves various physiological states. For instance, deep sleep can be influenced by diet. However, no study compared deep sleep after unhealthy versus healthy diets in the same person.
This is crucial because rest is dynamic, consisting of different stages with distinct functions and brain activity patterns. Understanding how diets affect these stages is essential, as factors like insomnia and aging can also impact sleep quality.
The study had 15 healthy young men who spent days in a sleep lab. They ate healthy and unhealthy diets, with calories matching their needs. An unhealthy diet has more sugar, fat, and processed foods. They ate each diet for a week while their sleep and activities were monitored.
Participants were observed in a sleep lab after each diet. Their brain activity was usually measured while they slept. Then, they stayed awake before catching up on sleep. Results showed they slept simultaneously on both diets without changing sleep stages.
However, deep sleep could have been more restorative after junk food, even on subsequent nights with a healthy diet. This suggests diet can affect sleep quality, similar to effects seen with aging and insomnia.
Researchers need to find out how long the effects of an unhealthy diet on sleep last. They didn’t check whether shallow, deep sleep affects memory and other functions. They’re interested in testing memory function to see if it’s affected. They also want to know how long the effects last. They don’t understand which parts of the unhealthy diet made deep sleep worse.
Unhealthy diets often have more saturated fat and sugar and less fiber. They wonder if a specific substance affects sleep more. Their study was short, so a more prolonged, unhealthier diet might have more substantial effects.
Journal reference:
- Luiz Eduardo Mateus Brandão, Alexandru Popa, et al., Exposure to a more unhealthy diet impacts sleep microstructure during normal sleep and recovery sleep: A randomized trial. Obesity. DOI: 10.1002/oby.23787.