In a new study, researchers questioned 1,082 students at MacEwan University about the quality of their sleep, their eating habits, and any perceived link between the two, and found a strong association between nightmares and lactose intolerance — potentially because gas or stomach pain during the night affects people’s dreams.
Nielsen et al. find lactose intolerance may link consuming dairy, nightmares, and poor sleep. Image credit: Micha HNBS.
“Nightmare severity is robustly associated with lactose intolerance and other food allergies,” said Dr. Tore Nielsen, a researcher at the Université de Montréal.
“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!”
For the study, the authors 1,082 students at MacEwan University asked about sleep time and quality, dreams and nightmares, and any perceived association between different kinds of dreams and different foods.
They also asked about participants’ mental and physical health and their relationship with food.
About a third of respondents reported regular nightmares. Women were more likely to remember their dreams and to report poor sleep and nightmares, and nearly twice as likely as men to report a food intolerance or allergy.
About 40% of participants said that they thought eating late at night or specific foods affected their sleep; roughly 25% thought particular foods could make their sleep worse.
People who ate less healthily were more likely to have negative dreams and less likely to remember dreams.
“We are routinely asked whether food affects dreaming — especially by journalists on food-centric holidays. Now we have some answers,” Dr. Nielsen said.
Most participants who blamed their bad sleep on food thought sweets, spicy foods, or dairy were responsible.
Only a comparatively small proportion — 5.5% of respondents — felt that what they ate affected the tone of their dreams, but many of these people said they thought sweets or dairy made their dreams more disturbing or bizarre.
When the researchers compared reports of food intolerances to reports of bad dreams and poor sleep, they found that lactose intolerance was associated with gastrointestinal symptoms, nightmares, and low sleep quality.
It’s possible that eating dairy activates gastrointestinal disturbance, and the resulting discomfort affects people’s dreams and the quality of their rest.
“Nightmares are worse for lactose intolerant people who suffer severe gastrointestinal symptoms and whose sleep is disrupted,” Dr. Nielsen said.
“This makes sense, because we know that other bodily sensations can affect dreaming.”
“Nightmares can be very disruptive, especially if they occur often, because they tend to awaken people from sleep in a dysphoric state.”
“They might also produce sleep avoidance behaviors.”
“Both symptoms can rob you of restful sleep.”
The findings appear in the journal Frontiers in Psychology.
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Tore Nielsen et al. 2025. More dreams of the rarebit fiend: food sensitivity and dietary correlates of sleep and dreaming. Front. Psychol 16; doi: 10.3389/fpsyg.2025.1544475