Is the cheese or yogurt you enjoy in the evening would your nightmare source? Canadian researchers suggest a link between bad dreams and lactose intolerance, probably due to the digestive symptoms it causes.
Popular wisdom has said it for a long time: it is better to be a light dinner to sleep well. But little scientific research has explored the influence of food on dreams.
For a study published Tuesday in Frontiers in Psychology, researchers in psychology interviewed for four months 1,082 students from Macewan University (Canada) about their eating habits, their sleep and more specifically their nightmares, and the link they made between the two.
About 40% of the participants estimated that their diet was playing on the quality of their sleep, including 24.7% by degrading it. And 5.5% thought she had influenced their dreams.
Desserts/sweets and dairy products were cited by respondents such as foods affecting the quality of their sleep the most (22.7% and 15.7% respectively) and their dreams (29.8% and 20.6%) by making them “bizarre” 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.
The authors compared these declarations to those on their food intolerances and found a strong association between nightmares and lactose intolerance.
Subtle signals
Many people intolerant to lactose “still consume dairy products”, intolerance varying in intensity according to the quantity of lactase (the enzyme which digests lactose) that each produced in its small intestine, reminds AFP Tore Nielsen, specialist in neurophysiology and neurocognition of dreams and nightmares at the University of Montreal and the main author of the study.
When they sleep, these people can therefore feel, consciously or not, “subtle somatic and organic signals” associated with gastrointestinal symptoms (bloating, cramps …) after the consumption of dairy products.
However, previous studies have brought evidence that certain dreams “capture unconscious bodily disorders which do not manifest themselves until later in the form of visible symptoms”, underlines the researcher. Thus, “dreaming of a fire can precede a fever of a fever”.
Another explanation could be negative emotions, such as anxiety, linked to gastrointestinal symptoms. “We know that the negative emotions experienced in the waking state can be prolonged in dreams. The same goes for those that emerge because of digestive disorders that occurred during sleep, “explains Dr. Nielsen.
However, the study did not draw a link between gluten intolerance and nightmares, perhaps because of its low prevalence in the sample. Or because gluten intolerance “produces different physiological or emotional effects,” he says.
Although the link between lactose intolerance and nightmares seem robust, the researchers wonder about how it works: do participants sleep badly because they eat less well? Or are they eating less because they sleep badly? Unless another factor affects both diet and sleep …
“We must conduct other studies on more people of different ages, from various environments and with different eating habits to see if these results are generalizable,” said Nielsen, who is already thinking with his colleagues at future research.
An “ideal experience” would consist in randomly distributing participants who have or not lactose intolerance in assigned groups to consume specific foods before sleeping, then collecting and analyzing their dreams. A group could consume conventional dairy products before bedtime, while another group would consume lactose-free dairy products, “in order to determine if the effects of milk are limited to those with this condition,” he explains.
