Scientists have confirmed a link between dairy products and nightmares

A new study published in Frontiers in Psychology has found that people with lactose intolerance are more likely to have nightmares and their sleep is of lower quality. According to scientists, this is due to the abdominal pain sensations that trigger disturbing dreams.

"The severity of nightmares is significantly associated with lactose intolerance and other food allergies," said lead study author Dr Thor Nielsen from the University of Montreal. "These new findings suggest that changing food habits in people with food sensitivities may lessen nightmares. It also explains why it is so often dairy products that are blamed for bad dreams."

There is a long-held belief that food affects sleep. To test this, researchers surveyed 1,082 students at McEwan University in Canada. They were asked about the length and quality of their sleep, the content of dreams and nightmares, as well as their attitudes towards food and a possible link between food and nighttime experiences.

About a third of participants reported having nightmares regularly. Women were more likely to remember their dreams, more likely to complain of poor sleep and almost twice as likely as men to report food allergies. About 40 per cent of respondents believed that eating before bed or certain foods affected their sleep; about 25 per cent believed certain foods made it worse.

Nielsen emphasises: "We get asked all the time whether food affects sleep - especially on food-related holidays. Now we have some answers."

The majority of participants who blamed food for disrupting sleep cited sweets, spicy foods and dairy products as culprits. While only 5.5 per cent of respondents directly linked dreams to the food they consumed, it was among those who were more likely to believe that sweets and dairy caused disturbing or strange dreams.

The authors found that people with lactose intolerance were more likely to have GI symptoms, nightmares and poor sleep quality. Perhaps dairy products cause physical discomfort, and it affects sleep patterns and dream content.

"Nightmares are particularly pronounced in people with severe GI symptoms and sleep disturbances," Nielsen notes. - "This makes sense: bodily sensations are known to influence dreams. Nightmares can awaken a person in an anxious state, leading to sleep avoidance and, as a result, chronic sleep deprivation."

Interestingly, fewer participants in the current study linked dreams to food compared to a similar survey that Nielsen and colleague Russell Powell conducted 11 years ago. Researchers believe this may be due to students' increased awareness of food intolerances - they may have simply started avoiding foods that provoke discomfort.

While the study confirmed a strong link between lactose intolerance and nightmares, the overall picture remains unclear. The researchers don't rule out the possibility that poor sleep may lead to poor nutrition rather than the other way round. It's also possible that both factors are influenced by some third cause.

"We need to study more people of different ages and with different eating habits to see how far our results can be generalised," Nielsen emphasises. - "We need experimental data as well. We are planning a study where one group will eat cheese before bed and the other group will eat a neutral product to see if it affects sleep quality and dream content."

Read more: More dreams of the Rarebit Fiend: Food sensitivity and dietary correlates of sleep and dreaming, Frontiers in Psychology (2025). DOI: 10.3389/fpsyg.2025.1544475