Your sleep might not be restful if there are visions of sugar plums dancing in your head — or your gut.
A new study finds that eating a junk food diet filled with sugar, saturated fat and processed foods results in poor sleep quality.
And when the participants in that study were switched to a healthier diet, their sleep quality improved.
“Both poor diet and poor sleep increase the risk of several public health conditions,” Jonathan Cedernaes, study co-author and associate professor at Uppsala University in Sweden, said in a news release.
Sleep problems have been linked to an increased risk of hypertension, diabetes, obesity, depression, heart attack and stroke, according to the National Institutes of Health.
“[N]o study had previously investigated what happens if we consume an unhealthy diet and then compared it to quality of sleep after that same person follows a healthy diet,” Cedernaes added.
The researchers asked 15 healthy young male volunteers to follow a healthy diet, and an unhealthy diet, in a random order for one week. Each diet contained roughly the same amount of calories.
Pizza, sugary cereal, meatballs and chocolate wafers were the mainstays of the unhealthy diet. The healthier diet contained unsweetened yogurt, muesli, salmon and vegetables.
The unhealthy diet contained nearly double the amount of fat — 44% versus 23% — of the healthy diet, and almost double the amount of sugar, too (17% versus 9%).
The participants’ sleep was measured in a sleep laboratory with polysomnography, which uses a device that measures brain waves, oxygen levels in the blood, heart rate, breathing and eye movements, according to the Mayo Clinic.
The results, reported in the journal Obesity, showed that the men slept about the same amount of time, and spent the same amount of time in different stages of sleep, regardless of their diet.
But after eating an unhealthy diet, during a deep sleep stage of rest, the amount of slow-wave activity in the men’s brains was reduced.
Slow-wave brain activity is one measure of how restorative sleep is, and insulin sensitivity and the secretion of growth hormones have been linked to slow-wave sleep.
“Intriguingly, we saw that deep sleep exhibited less slow-wave activity when the participants had eaten junk food, compared with consumption of healthier food,” Cedernaes said. “Essentially, the unhealthy diet resulted in shallower deep sleep.”
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The study authors noted that their investigation was limited by the participants selected, all of whom were physically active young men with no obesity or weight issues, and by the fact that there were only 15 participants.
“Currently, we do not know which substances in the unhealthier diet worsened the depth of deep sleep,” Cedernaes said. “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.”