Researchers examined data from food diaries for more than 50,000 women in their mid-60s who had already gone through menopause, a transition that is also associated with an increased risk of sleep problems and insomnia. They focused on the “dietary glycemic index,” a measure of how many foods people consume that can contribute to spikes in blood sugar levels.
Women with the highest dietary glycemic index scores - meaning they consumed more refined carbohydrates like white bread, sweets and sugary soda - were 11% more likely than women with the lowest scores to report insomnia at the start of the study period.
They were also 16% more likely to develop new insomnia during the three-year follow-up period.
“Our results point to the importance of diet for those who suffer from insomnia,” said lead study author James Gangwisch of the Columbia University Vagelos College of Physicians and Surgeons in New York City.
“Avoiding insomnia is therefore another good reason to avoid sweets besides weight control,” Gangwisch said by email.
While the study wasn’t designed to prove whether or how eating too many sweets and refined carbs might cause insomnia, it’s possible that hormonal changes may play a role.
“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,” Gangwisch said.
Insomnia disproportionately affects women, the study team notes in the American Journal of Clinical Nutrition.
In the study, women whose diet included higher amounts of vegetables, fiber and whole fruit (not juice) were less likely to have or develop problems with insomnia. Even though whole fruits contain sugar, they also contain fiber that helps minimize spikes in blood sugar, making these foods lower on the dietary glycemic index.
One limitation of the study is that researchers didn’t objectively measure food intake, the quantity or quality of sleep, or any shifts in blood sugar or hormones.
It’s also possible that chronic insomnia contributed to cravings for carbs or sweets, rather than women developing insomnia as a result of eating too much sugar and refined grains, Jose Ordovas, director of Nutrition and Genomics at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, pointed out.
“Using these findings as the basis for prevention and treatment of insomnia is extremely premature,” Ordovas, who wasn’t involved in the study, said by email.
Doctors often recommend a low-glycemic diet to people who need to lower or control their blood sugar, including individuals with diabetes, or who need to lose weight or develop healthier eating habits.
Better sleep could be yet another reason to eat this way, Gangwisch said.
“The take-home message here is to limit the consumption of highly processed carbohydrates such as added sugars since they could contribute toward or exacerbate insomnia,” Gangwisch said.