Consuming Dairy Before Sleep May Lead to Nightmares, Research Indicates

Has a late-night cheese session ever seemed to send you down your own personal Nightmare on Elm Street? You’re probably not alone. Research out today has revealed a link between lactose intolerance and a higher risk of bad dreams.

Scientists in Canada conducted the study by surveying college students. People who reported having regular nightmares and poorer sleep in general were also more likely to report having food allergies, including lactose intolerance, they found. The researchers speculate that the distress caused by people’s stomach issues can seep into our non-waking hours.

“The results we obtained confirmed our hypothesis that lactose intolerance is indeed predictive of disturbed dreaming and nightmares,” study co-author Ross Powell, a psychologist and professor emeritus at MacEwan University in Edmonton, Alberta, told Gizmodo.

The idea that the foods we eat, particularly cheese or other dairy products, can worsen our sleep is hardly new. In the early 1900s, for example, American cartoonist Winsor McCay created a popular newspaper comic strip—Dream of the Rarebit Fiend—that routinely featured people getting nightmares or strange dreams after eating something less than agreeable. Often, this trigger food was a Welsh rarebit, a popular British dish of cheese on toast.

But according to Powell, this phenomenon hasn’t really been studied much scientifically. A decade ago, this same team published a survey finding that roughly 20% of participants reported having bizarre dreams they felt were connected to eating certain foods or eating late at night, with many blaming dairy products specifically. In their latest study, Powell and his colleagues were hoping to replicate their earlier findings, in addition to digging a bit deeper into the reasons behind people’s cheese-flavored nightmares.

The researchers surveyed over 1,000 college students (more than twice the sample size of the 2015 study) about their dietary and sleeping habits. About 40% of respondents felt that some foods or late-night chowing affected their sleep, with 25% feeling their diets worsened their sleep. This time, only 5.5% specifically blamed foods for affecting the content of their dreams, but dairy, spicy foods, and sweets were commonly blamed culprits among those who did. The researchers also found that self-reported lactose intolerance was associated with more severe nightmares and poorer sleep, as were other food allergies. Unsurprisingly, lactose intolerance was associated with gastrointestinal symptoms, while people who reported less healthy diets in general tended to have more nightmares and to have more difficulty recalling their dreams.

The team’s findings were published Tuesday in Frontiers in Psychology (both the current and the 2015 study directly reference Dream of the Rarebit Fiend in their title).

As anyone with lactose intolerance knows, indulging a dairy craving can cause plenty of GI pain and bloating. And the researchers reason that these symptoms can stir people awake or more subtly ruin their dreams—an explanation that might extend to other similar kinds of pain.

“It may be that GI distress, in comparison to other types of physical distress, has a particularly strong impact upon sleeping and dreaming. Menstrual cramping, for example, has also been shown to increase the likelihood of disturbed dreaming,” Powell said. He further theorizes that since GI symptoms can be caused by ingesting poison, our dairy nightmares might be the body’s way to keep itself alert in case of medical emergency.

The researchers would like to confirm their research experimentally, such as a trial that directly compares how lactose-intolerant people sleep and dream after either eating or avoiding dairy. Powell believes it would also be interesting to study whether food sensitivities could be directly contributing to some people’s nightmare disorders.

Around one-third of Americans have trouble digesting lactose, though not everyone feels sick after having some. And given how annoying lactose intolerance already is, these findings may offer further incentive to stay away from the late-night dairy. I personally know that I’ll be more likely to reach for a scoop of evening sorbet over the ice cream next time around.