Could the cheese or yogurt you eat at night be the source of your nightmares? Canadian researchers suggest a link between bad dreams and lactose intolerance, likely due to the digestive symptoms it causes.
Popular wisdom has long held that a light dinner is better for a good night's sleep. But little scientific research has explored the influence of diet on dreams.
For a study published Tuesday in Frontiers in Psychology, psychology researchers surveyed 1,082 students at MacEwan University in Canada for four months about their eating habits, sleep, and more specifically, nightmares, and the connection they made between the two.
About 40% of participants felt that their diet affected the quality of their sleep, including 24.7TP3T by worsening it. And 5.5TP3T thought it influenced their dreams.
Desserts/sweets and dairy products were cited by respondents as the foods that most affected the quality of their sleep (22.7% and 15.7% respectively) and their dreams (29.8% and 20.6%) by making them “weird” or “disturbing”.
On the contrary, fruits (17.6%), vegetables (11.8%) and herbal teas (13.4%) were most often identified as contributing to a good night's sleep.
The authors compared these statements to those about their food intolerances and found a strong association between nightmares and lactose intolerance.
– Subtle signals –
Many people with lactose intolerance "still consume dairy products," with the intolerance varying in intensity depending on the amount of lactase (the enzyme that digests lactose) that each person produces in their small intestine, Tore Nielsen, a specialist in neurophysiology and neurocognition of dreams and nightmares at the University of Montreal and lead author of the study, told AFP.
When they sleep, these people can therefore feel, consciously or not, “subtle somatic and organic signals” associated with gastrointestinal symptoms (bloating, cramps, etc.) after consuming dairy products.
However, previous studies have provided evidence that some dreams "capture unconscious bodily disturbances that only later manifest themselves as visible symptoms," the researcher points out. For example, "dreaming about a fire can precede a fever."
Another explanation could be negative emotions, such as anxiety, linked to gastrointestinal symptoms. "We know that negative emotions experienced during waking hours can carry over into dreams. The same is likely true for those that arise from digestive disturbances during sleep," explains Dr. Nielsen.
The study, however, did not establish a link between gluten intolerance and nightmares, perhaps due to its low prevalence in the sample. Or because gluten intolerance "produces different physiological or emotional effects," he suggests.
Although the link between lactose intolerance and nightmares appears robust, researchers are wondering how it works: Are participants sleeping poorly because they're eating less well? Or are they eating less well because they're sleeping poorly? Or is there another factor affecting both eating and sleeping?
"We need to conduct more studies on more people of different ages, from different backgrounds, and with different eating habits to see if these results are generalizable," says Nielsen, who is already thinking with his colleagues about future research.
An "ideal experiment" would involve randomly assigning participants with and without lactose intolerance to groups assigned to consume specific foods before bed, and then collecting and analyzing their dreams. One group could consume regular dairy products before bed, while another group would consume lactose-free dairy products, "to determine whether the effects of milk are limited to those with this condition," he explains.
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