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Can't sleep at night?

Researchers say the reason – and the solution – could be lurking in your kitchen. The ingredients for poor sleep can be found in every meal, and the less you sleep, the more likely you may be to consume them.

"It's a cycle," said Dr. Marie-Pierre St-Onge, an associate professor of nutritional medicine in the division of general medicine at Columbia University in New York City. "How you sleep at night influences what you eat during the day, and what you eat during the day influences how you sleep at night."

Average sleep duration has been shrinking over the past several decades, concurrent with the rise in obesity and diabetes. This led St-Onge and her colleagues to investigate how diet and meal composition might be affecting sleep. They were particularly interested in the role carbohydrates, which affect blood glucose levels, might play.

Eating carbohydrates makes blood glucose, or blood sugar, rise. But how much and how fast differs by the type of carbohydrate. The glycemic index was created to measure how much a food boosts blood glucose levels. Foods with a high glycemic index are digested faster and cause spikes in blood sugar and insulin, a hormone that regulates blood sugar in the body. Those lower on the glycemic index are digested more slowly and have a smaller impact on blood sugar levels.

Foods low on the glycemic index include many that promote cardiovascular health. Among them are certain fruits such as apples and oranges; vegetables; minimally processed grains such as barley and quinoa; beans; low-fat dairy; and nuts. Examples of foods that lower cardiovascular health and also are high on the glycemic index include white bread, rice cakes, crackers, bagels, donuts, many packaged breakfast cereals, baked potatoes and corn.

In a 2020 study in the , St-Onge and her colleagues showed eating a high glycemic index diet could be a risk factor for insomnia in postmenopausal women. A 2020 analysis of 24 studies in the found sleeping 5.5 hours or less per night was linked to eating more food overall, with a higher intake of the macronutrients (fat, protein and carbohydrates) that together make up total calorie consumption.

Research has found for years that when people get less sleep, they tend to eat more calories and fat, offering a potential explanation for the link between short sleep and a higher risk for obesity. Even mild sleep deprivation has been linked to poor food choices among children, who overeat when tired.

St-Onge, author of "Eat Better, Sleep Better," said it's likely because not getting enough sleep can alter the brain's response to food. Some of her earlier work, including a 2012 study in the journal , found that shorter sleep duration influenced hormone production and did so differently for men and women. Among men, getting less sleep increased levels of ghrelin, the hormone that controls hunger. Among women, it altered levels of GLP-1, reducing satiety, meaning women felt less full after eating.

So what foods should people eat if they want to sleep better?

"You should eat a healthful diet throughout the day to have healthy sleep at night," St-Onge said. "Legumes and whole grains are particularly good at being protective against sleep disorders."

Studies show adherence to the Mediterranean-style eating pattern, associated with better cardiovascular health, can also be good for better sleep. In addition to legumes and whole grains, the Mediterranean-style diet includes a focus on fruits and vegetables, low-fat dairy, lean meats and fish, as well as cooking with olive oil.

A in Sleep found people who stuck to a Mediterranean diet were less likely to experience insomnia and more likely to get adequate sleep. A in the journal Nutrients that looked at diet and sleep among women found better adherence to the Mediterranean diet – especially fruits, vegetables and legumes – was linked to better sleep quality or fewer sleep disturbances.

"Relatively speaking, the same foods that are good for metabolic health are good for promoting good sleep," said Dr. Maya Vadiveloo, an associate professor in the department of nutrition at the University of Rhode Island College of Health Sciences in Kingston.

Of course, diet isn't the only factor affecting sleep, Vadiveloo said. "There are a lot of reasons people have trouble sleeping."

Stress, a noisy environment, not getting enough physical activity during the day and exposure to light from devices such as cellphones, laptops and tablets are among the factors that can disrupt sleep, she said.

Other diet-related factors, such as eating too late at night or consuming spicy or citric foods that increase acid reflux, can also disrupt sleep, Vadiveloo said. "Any type of discomfort is going to disrupt your sleep."

But those factors differ from person to person, she said. "It's not a one-size-fits-all approach."

Vadiveloo suggested keeping a food-and-mood log to help people identify what works and what doesn't to improve the quality and quantity of their sleep.

"Notice the connections between when you feel stressed and what you ate," she said. "What did you eat on nights you felt well rested? What about when it took a long time to fall asleep, or you woke up a lot during the night? Track this over time and notice the patterns."