Study details and key findings

For the study, researchers surveyed 1,082 undergraduate psychology students at the MacEwan University in Canada about their diet, food sensitivities, sleep habits, dream recall, frequency of nightmares, and more.

Overall, around 40% of respondents said they thought eating late at night or eating specific foods could impact their sleep. Roughly 25% of respondents said that eating certain foods before bed worsened their sleep, while a little over 20% said some foods improved their sleep.

Among respondents who said they had more nightmares after eating certain foods, 31% believed desserts or other sweets were the cause, 22% blamed dairy products, 16% blamed meats, and 13% blamed spicy foods.

After comparing reports of food intolerances to reports of poor sleep and nightmares, the researchers found that lactose intolerance was associated with gastrointestinal symptoms, nightmares, and poor sleep quality. According to the researchers, eating dairy, including cheese, could lead to gastrointestinal disturbance, which could make people uncomfortable and affect their sleep and dreams.

Commentary

According to Marie-Pierre St-Onge, director of the Center of Excellence for Sleep & Circadian Research at Columbia University Irving Medical Center, sleep disturbances caused by gastrointestinal issues may explain the link between certain foods and poor sleep or nightmares.

"If you have GI issues, that could account for a lot of what's happening in terms of your sleep disturbances that could be associated with different dreams," St-Onge said.

Similarly, Patrick McNamara, an associate professor of neurology at the Boston University Chobanian & Avedisian School of Medicine, said eating a trigger food for lactose intolerance could lead to "micro-arousals" that negatively impact sleep quality, which then lead to stronger nightmares.

The researchers also noted that food-related nightmares could be linked to depression and anxiety. Some symptoms of lactose intolerance, including bloating, cramping, and gas, can directly impact a person's mood, which can continue into sleep and cause bad dreams. In an earlier 2005 study from Nielsen, he found that "dreaming is more emotionally intense and conflictual when abdominal cramping is at its worst," including during menstruation.

Overall, the study's findings suggest that "changing eating habits for people with some food sensitivities could alleviate nightmares," Nielsen said. "They could also explain why people so often blame dairy for bad dreams!"

Going forward, more research is needed on the potential link between certain foods and sleep quality, with Nielsen saying that he wants to see more research specifically on the link between dairy and dreams.

"We need to study more people of different ages, from different walks of life," Nielsen said. "Experimental studies are also needed to determine if people can truly detect the effects of specific foods on dreams. We would like to run a study in which we ask people to ingest cheese products versus some control food before sleep to see if this alters their sleep or dreams."