Eating cheese at night... can it cause nightmares?

Could the cheese or yogurt a person eats at night be the source of their nightmares? This question seems to be seriously being raised after Canadian researchers concluded there is a link between disturbing dreams and lactose intolerance, likely due to the digestive symptoms it causes. It has long been known, according to popular wisdom, that eating a light dinner helps promote restful sleep. But little scientific research has explored the effect of diet on dreams. In a study published Tuesday in the journal Frontiers in Psychology, psychology researchers surveyed 1,082 students at Canada's MacEwan University over a four-month period about their eating habits and sleep, and more specifically, their nightmares, and the link they found between the two. About 40% of participants felt that their diet affected the quality of their sleep, including 24.7% who said it had a negative effect, while 5.5% said it affected their dreams. Participants in the study reported that sweets and dairy products were the foods that most affected their sleep quality (22.7% and 15.7%, respectively) and their dreams (29.8% and 20.6%), making them seem "weird" or "disturbing." In contrast, fruits (17.6%), vegetables (11.8%), and herbal teas (13.4%) were identified as the foods that most helped them get a good night's sleep. The researchers compared these statements with those of Related to their food intolerance, they found a close link between nightmares and lactose intolerance. Tore Nielsen, a specialist in neurophysiology and neurocognition of dreams and nightmares at the University of Montreal, the study's lead author, told AFP that many people with lactose intolerance "still consume dairy products," and the severity of intolerance varies depending on the amount of lactase (the enzyme that digests lactose) each person produces in their small intestine. Therefore, these people may experience, while sleeping, whether consciously or unconsciously, "subtle physical and physiological signals" related to gastrointestinal symptoms (including bloating and cramps) after consuming dairy products. However, previous studies indicate that some dreams "record subconscious physical disturbances that only later appear as visible symptoms." For example, "seeing a fire in a dream can precede a fever." This could also be explained by negative emotions, such as anxiety, associated with gastrointestinal symptoms. "We know that negative emotions experienced while awake can extend to dreams," Nielsen explains. "The same is likely true for those that arise from gastrointestinal disturbances during sleep." However, the study did not prove a link between gluten intolerance and nightmares, perhaps because of its limited prevalence in the sample, or because gluten intolerance "produces different physiological or emotional effects," according to Nielsen. Although the link between lactose intolerance and nightmares appears strong, the researchers wonder how it works: Do participants sleep poorly because they eat less-quality food? Or do they eat less-quality food because they sleep poorly? Unless there's another factor influencing both diet and sleep, Nielsen says, "We need to conduct more studies with more people of different ages, backgrounds, and eating habits to see if these findings are generalizable." He and his colleagues are already considering future research. The "ideal experiment" would randomly assign participants, whether lactose intolerant or not, to groups assigned to eat specific foods before bed, then collect and analyze their dream data. One group could eat regular dairy products before bed, while the other could eat lactose-free dairy products, "to determine whether the effects of milk are specific to people with this condition," Nielsen says.