Association Between Fermented Food Consumption and Sleep Quality Under Psychological Stress: Prospective Cohort Study

Sleep quality might be dependent on the gut-brain axis that employs gut microbiota. As, in adulthood, diet has the greatest influence on microbiota, the aim of the study was to investigate whether the consumption of fermented food was associated with sleep quality among medical students under exam stress. A prospective cohort questionnaire-based study was conducted online on a group of medical students under exam stress from the Medical University of Lodz, Poland. The participants were asked to provide information regarding their health and sleep quality (Pittsburgh Sleep Quality Index, PSQI) in the last week before the exam. During the 4 days before the exam, the participants were recording the consumption of various types of food and beverages, including fermented food. The study sample was 280 medical students (their mean age was 22.63, 172 were female). Students whose fermented food consumption was found in the second tercile had higher sleep quality under stress (mean PSQI 5.13) than students in the first (mean PSQI 5.73) and third (mean PSQI 6.17) terciles of fermented food consumption (p = 0.021). There was no association between the fermented food consumption and gastrointestinal symptoms under stress, even though, in general, the more symptomatic the students were, the worse sleep quality they had. Nonlinear association between fermented food consumption and sleep quality sets thinking about the complexity of biological mechanisms in which gut microbiota could possibly impact sleep under stress. The influence of widely available fermented food on sleep requires further study.