I like to tell my clients that “sleep is good food.” It turns out that good food could mean better sleep too, while less nutritious options may have a negative impact on sleep health.

New research out of Uppsala University has evaluated the impact of junk food on sleep. Healthy subjects ate a nutritious diet as well as a less healthy diet in randomized order. The quality of sleep declined after consuming an unhealthier diet compared to those eating healthier food. Results can be found in the journal Obesity.

Previous epidemiological research has indicated that our diet is linked with changes in sleep. But limited studies have evaluated how diet itself impacts sleep directly. One way to prove this is to have the same subjects eat different diets in randomized order.

Jonathan Cedernaes, Physician and Associate Professor in Medical Cell Biology at Uppsala University notes, "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 research has indicated that diets with more sugar content are associated with poor sleep. Sleep affects various physiologic states, according to Cedernaes. Deep sleep may be impacted by what we eat but past research hasn’t evaluated what occurs if we eat an unhealthy diet and then compared it to the quality of sleep after the same person eats a healthy diet.

He further notes that sleep is very dynamic. Sleep is made up of different stages with different functions including deep sleep, which modulates the release of hormones. In addition, sleep stages are recognized by various types of electrical activity in the brain. This impacts how restorative sleep is and varies depending on the brain region. Insomnia and aging can negatively impact the quality of sleep stages. Past research has not investigated if changes in sleep stages can happen due to exposure to different food consumed.

The small study included 15 healthy, normal-weight, young men who were monitored in a sleep lab. Subjects were initially screened for sleep habits, which had to be normal and within the advised range of an average of seven to nine hours of sleep each night.

Subjects were given both a healthier diet and one with more junk food in random order. Calories were the same in each diet but adjusted to the individual’s daily needs. The unhealthy diet was higher in sugar and saturated fat and contained more processed foods. The meals of the varying diets had to be eaten at individually adjusted times that were correlated across the two dietary conditions. The different diets were eaten for a week while the subjects’ sleep, activity, and meal times were measured at an individual level.

Subjects were evaluated in a sleep lab after each diet. In the lab, they were initially allowed to sleep a normal night, while their brain activity was checked to monitor their sleep. Subjects were then kept awake in the sleep lab before being allowed to make up sleep. Sleep was recorded in this stage as well.

The researchers observed that the subjects slept for the same amount of time when they ate the two diets. This occurred while they were adhering to the diets in addition to after they had switched to another, identical diet.

Subjects also spent the same amount of time in the different stages of sleep. The researchers were most keenly interested in evaluating the properties of the subjects’ deep sleep. Slow wave activity which measures how restorative deep sleep is, was impacted by junk food consumed. This effect continued into a second night once the participant’s diets were switched to an identical diet. In short, the unhealthy diet resulted in poorer deep sleep.

Similar changes in sleep are seen with aging and insomnia. A healthy diet should be encouraged for better sleep. The study did not show how long an unhealthy diet could affect sleep and didn’t investigate whether poorer sleep could change functions that are usually regulated by deep sleep.

Cedernaes.notes, "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.”

Poor-quality diets contain more saturated fat and sugar and less dietary fiber. Cedernaes thinks studying other dietary components and their role in sleep quality would be interesting. His diet intervention was also short and the sugar and fat content was moderate. He notes that an even unhealthier diet could have a more deleterious effect on sleep quality.

Want to improve your sleep? Below are some tips:

·         Skip the coffee, caffeinated tea, energy drinks, and other sources of caffeine after 2:00 PM.

·         Go to bed and wake up at around the same time each night and day.

·         Turn off the screens! This includes the TV, your tablet, phone, or any other light-emitting electronics.

·         Don’t eat heavy meals, especially close to bedtime. Limit fried food, fast food, and sugary treats throughout the day.

·         Limit alcohol consumption. It may put you to sleep initially but is known to interrupt sleep overall and increase hot flashes in women.

·         Eat lima beans! One study of medical students found that sleep was improved with the consumption of this starchy bean. 2

·         Do regular exercise most days of the week. Walking is one of the best ones, especially in older adults. 3

·         Don’t drink water too close to bedtime. Space it out throughout the day.

·         See a sleep specialist if you’re chronically tired. Sleep apnea impacts 5 to 10% of the population worldwide. 4

Lisa Andrews, MEd, RD, LD

References:

1. Luiz Eduardo Mateus Brandão, Alexandru Popa, Erasmus Cedernaes, Christopher Cedernaes, Lauri Lampola, Jonathan Cedernaes. Exposure to a more unhealthy diet impacts sleep microstructure during normal sleep and recovery sleep: A randomized trial. Obesity, 2023; DOI: 10.1002/oby.23787

2. Nisar M, Mohammad RM, Arshad A, Hashmi I, Yousuf SM, Baig S. Influence of Dietary Intake on Sleeping Patterns of Medical Students. Cureus. 2019 Feb 20;11(2):e4106. doi: 10.7759/cureus.4106. PMID: 31058000; PMCID: PMC6476615.

3. Hasan F, Tu YK, Lin CM, Chuang LP, Jeng C, Yuliana LT, Chen TJ, Chiu HY. Comparative efficacy of exercise regimens on sleep quality in older adults: A systematic review and network meta-analysis. Sleep Med Rev. 2022 Oct;65:101673. doi: 10.1016/j.smrv.2022.101673. Epub 2022 Aug 27. PMID: 36087457.

4. Sleep Apnea: What It Is, Causes, Symptoms & Treatment (clevelandclinic.org)