Eating Dairy Products Can Cause Nightmares, Study

University of Montreal scientists have found that eating too much dairy could ruin your sleep. The team questioned more than 1,000 students 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. 

“Nightmare severity is robustly associated with lactose intolerance and other food allergies,” said Tore Nielsen, lead author of the article in Frontiers in Psychology. “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!”

The team surveyed 1,082 students and found that about one-third of respondents had 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.

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,” said Nielsen. “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.”

However, besides the robust link between lactose intolerance and nightmares, it’s not clear how the relationship between sleep and diet works. It’s possible that people sleep less well because they eat less well, but it’s also possible that people don’t eat well because they don’t sleep well, or that another factor influences both sleep and diet. Further research is needed to confirm these links and identify the underlying mechanisms.