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Study links a carb-heavy diet to an increased risk of insomnia

One in four American adults experiences acute insomnia each year, researchers have found.

Photo by Kinga Cichewicz on Unsplash
One in four American adults experiences acute insomnia.
The American diet — particularly its emphasis on added sugars, processed grains and other refined carbohydrates — may be to blame, at least in part, for why so many American adults struggle with insomnia, according to a study published in the American Journal of Clinical Nutrition.

The study found that older women who ate the highest amount of refined carbohydrates were most likely to report having difficulty getting a good night’s sleep.

Women who ate the highest amount of whole fruit, vegetables and fiber, on the other, were least likely to report problems with insomnia.

Because of the way foods interact with the human body, these findings are likely applicable to other people, the study’s authors add.

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“Insomnia is often treated with cognitive behavioral therapy or medications, but these can be expensive or carry side effects,” says James Gangwisch, the study’s senior author and an assistant professor of clinical psychology at Columbia University, in a released statement.

“By identifying other factors that lead to insomnia, we may find straightforward and low-cost interventions with fewer potential side effects,” he adds.

A major health concern

Insomnia is a widespread health problem in the United States. One in four American adults experiences acute insomnia (difficulty falling or staying asleep for at least three nights a week) each year, researchers have found. About a quarter of those individuals have recurring bouts of insomnia or go on to develop chronic insomnia (when the problem continues for more than three months).

As I’ve noted here before, getting less than the recommended seven hours of sleep each night is harmful to our health. Insufficient sleep has been linked to obesity and a variety of negative health outcomes, including heart disease, diabetes and depression. Insufficient sleep also increases the risk of injuries from accidents and mental errors, both on and off the job.

Several previous studies have examined a possible link between a high-carb diet and insomnia. The results of those studies were inconsistent, however. Nor were the studies able to clearly determine if a high-carb diet led to insomnia, or whether insomnia caused individuals to crave — and eat — more sugary foods.

Study details

For the current study, Gangswich and his colleagues decided to look at the development of insomnia over time in people with different types of diets. To do this, they used data collected from more than 50,000 women who were recruited into a large research project known as the Women’s Health Initiative during the 1990s, when the women were between the ages of 50 and 79.

The women filled out detailed questionnaires when they entered the study. The questions included ones about their diets and their sleep habits. Three years later, they filled out a second sleep assessment.

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From the original questionnaire, the researchers determined each woman’s dietary glycemic index — how likely the foods she ate would cause her blood sugar to rise quickly. Highly processed and/or sugar-sweetened foods (such as white bread, white rice, refined pasta, French fries, soft drinks and candies) have a high glycemic index, while minimally processed foods (such as whole-wheat bread and pasta, brown rice, legumes, vegetables and whole fruit) have a lower one.

The women were divided into five groups (quintiles) based on their dietary glycemic index. The researchers then compared those rankings to the women’s sleep assessments. They wanted to see if there was any link between the women’s dietary glycemic index and their risk of reporting insomnia three years later. (Almost 10,000 of the women reported insomnia at the second sleep assessment.)

After adjusting for a variety of other factors associated with insomnia (including age, weight, caffeine consumption, stressful life events, hypertension and an overactive thyroid), the researchers found that the higher the women’s dietary glycemic index, the greater their risk of developing insomnia.

They also found that women who consumed high amounts of fiber, whole grains, vegetables and whole fruit were significantly less likely to report problems with insomnia three years later.

Why would diet make a difference?

“When blood sugar is raised quickly, your body reacts by releasing insulin, and the resulting drop in blood sugar can lead to the release of hormones such as adrenaline and cortisol, which can interfere with sleep,” explains Gangwisch.

And, yes, fruits contain sugar. “But the fiber in them slows the rate of absorption to help prevent spikes in blood sugar,” says Gangwisch. “This suggests that the dietary culprit triggering the women’s insomnia was the highly processed foods that contain larger amounts of refined sugars that aren’t found naturally in food.”

Limitations and implications

This was an observational study, so it can’t prove a direct cause-and-effect relationship between diet and insomnia. Also, the women in the study self-reported the foods they ate and their sleep habits. Those reports may or may not have been accurate.

Still, the study’s findings are interesting. They also appear to be the most robust to date on this topic, for the study observed people over several years —rather than at one single point in time — to see if diet could be linked to the development of insomnia.

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“If high-[glycemic index] diets increase the risk of insomnia then dietary interventions that promote the consumption of whole unprocessed carbohydrates that are high in fiber and have low [glycemic index numbers] could serve as potential treatments of, and primary preventive measure for, insomnia,” conclude Gangswich and his colleagues in their paper.

Potential is the key word there. It’s not yet known if eating more fruits, veggies, whole grains and other healthful foods would actually help people sleep better.

“Based on our findings, we would need randomized clinical trials to determine if a dietary intervention, focused on increasing the consumption of whole foods and complex carbohydrates, could be used to prevent and treat insomnia,” says Gingwisch.

FMI: You’ll find an abstract of the study on the American Journal of Clinical Nutrition’s website, but the full study is behind a paywall.