A diet high in refined carbohydrates may trigger insomnia in older women.

That’s according to researchers who culled data from 50,000 food diaries from the Woman’s Health Initiative study. Their investigation showed that postmenopausal women who eat more highly refined carbohydrates are more likely to develop insomnia than women whose diet includes more fiber-rich foods. 

Foods with refined carbohydrates often contain added sugars. Among the most common are white bread, white rice, pastries and soda. Consuming them can cause blood sugar to spike, which prompts the body to release insulin. Blood sugar then drops, and hormones such as adrenaline and cortisol are released, explained James Gangwisch, Ph.D., from Columbia University Vagelos College of Physicians and Surgeons.

Those rapid spikes and troughs in blood sugar may be the culprit behind insomnia, the researchers theorized. In contrast, while high-fiber foods such as fruit may also contain sugar, their fiber content slows down the body’s absorption, preventing blood sugar spikes, Gangwisch reported. 

The findings may also extend to a broader population, since most people experience this rapid rise in blood sugar after eating refined carbohydrates, the researchers said.

An estimated 30% of adults have insomnia. While sleeplessness can be treated with cognitive behavioral therapy or medication, identifying insomnia triggers may lead to less expensive interventions with fewer side effects, the investigators concluded.

Full findings are available in The American Journal of Clinical Nutrition.