That late-night slice of pizza or bowl of mac and cheese might be doing more than giving you indigestion — it could be messing with your dreams.
A new study from researchers in Canada has found a strong link between food sensitivities — especially lactose intolerance — and nightmares. The study surveyed more than 1,000 college students about their eating habits, sleep quality and dream experiences. Those with lactose intolerance were significantly more likely to report disturbed sleep and unsettling dreams.
“Nightmare severity is robustly associated with lactose intolerance and other food allergies,” said Dr. Tore Nielsen of Université de Montréal, the study’s lead author. “These new findings imply that changing eating habits for people with some food sensitivities could alleviate nightmares. They could also explain why people so often blame dairy for bad dreams!”
Although only about 5% of participants believed that food directly influenced their dreams, many of those pointed to dairy or sweets as likely culprits. Among students who reported poor sleep, nightmares or dream-related disturbances, a notable share had diagnosed food intolerances — and most of those involved lactose.
The likely explanation? Stomach discomfort caused by lactose can disrupt sleep and trigger vivid or unpleasant dreams.
“Nightmares are worse for lactose intolerant people who suffer severe gastrointestinal symptoms and whose sleep is disrupted,” Nielsen explained. “This makes sense, because we know that other bodily sensations can affect dreaming.”
The study also found that people with unhealthy eating habits were more likely to have negative dreams, while those with food sensitivities who avoided trigger foods reported fewer issues than in previous studies, suggesting that dietary changes could improve both sleep and dream quality.
Still, researchers caution that the relationship between diet and sleep isn’t fully understood. It’s unclear whether poor diet leads to worse sleep or if poor sleep affects how people eat.
“We need to study more people of different ages, from different walks of life, and with different dietary habits to determine if our results are truly generalizable to the larger population,” Nielsen said.
The research, which was published in Frontiers in Psychology, was supported by the Natural Sciences and Engineering Research Council of Canada, including both a grant for Dr. Nielsen and a doctoral scholarship for co-author Christopher Pelletier-Drolet.
Next up? The team wants to test the cheese theory directly — by comparing people’s dreams after eating cheese at bedtime versus a non-dairy food.