Association Between Consumption of Fermented Food and Food-Derived Prebiotics With Cognitive Performance, Depressive, and Anxiety Symptoms in Psychiatrically Healthy Medical Students Under Psychological Stress: A Prospective Cohort Study

Abstract

BackgroundGut microbiota-based therapeutic strategies, such as probiotic and prebiotic preparations, may benefit mental health. However, commonly consumed fermented and prebiotic-containing foods have not been well-tested. The aim of the present study was to determine whether consumption of fermented food and food-derived prebiotics is associated with cognitive performance, depressive, and anxiety symptoms in psychiatrically healthy medical students under psychological stress.MethodsThe study protocol with data analysis plan was prospectively registered. Food consumption was evaluated with a 7-day dietary record. Cognitive performance was modeled with academic examination performance in relation to subject knowledge. Pre-exam depressive and anxiety symptoms were assessed with the Patient Health Questionnaire-9 and Generalized Anxiety Disorder-7, respectively.ResultsIn total, 372 medical students (22.7 ± 1.1 years of age, 66% female) completed the study. No relationship was observed between cognitive performance under stress and either fermented food (adjusted β 0.02, 95% CI −0.07–0.11, p = 0.63) or food-derived prebiotics consumption (adjusted β −0.00, 95% CI −0.09–0.09, p = 0.99). High intake of fermented food was associated with more severe depressive (adjusted β 0.11, 95% CI 0.01–0.20, p = 0.032) and anxiety symptoms under stress (adjusted β 0.13, 95% CI 0.04–0.22, p = 0.0065); however, no such link was observed for food-derived prebiotics (adjusted β 0.03, 95% CI −0.07–0.13, p = 0.50 and −0.01, 95% CI −0.11–0.08, p = 0.83, for depression and anxiety, respectively).ConclusionsUnder psychological stress in medical students, consumption of fermented food and food-derived prebiotics appears to be not associated with cognitive performance. High intake of fermented food, but not food-derived prebiotics, may be associated with severity of depressive and anxiety symptoms. The safety of fermented food in this regard therefore requires further clarification.

Who Benefits from Fermented Food Consumption? A Comparative Analysis between Psychiatrically Ill and Psychiatrically Healthy Medical Students

“…Similar to the healthy students [ 17 ], psychiatrically ill participants decreased their physical activity in the 7-day pre-exam period ( p = 0.0076). Their overall quality of diet did not significantly change ( p = 0.89), but they reported reduced consumption of margarine, butter, or meat fat ( p = 0.0077).…”

“…It has been reported in our previous study that under stress, the consumption of fermented food in psychiatrically healthy medical students was positively associated with the severity of depressive and anxiety symptoms, with a small effect size [ 17 ]. These findings were not replicated in the group of psychiatrically ill students.…”

“…In our previous study, the association between fermented food consumption and depressive and anxiety symptoms has been tested among psychiatrically healthy medical students under psychological stress [ 17 ]. In order to minimize observer bias, that study had no specific exclusion criteria and psychiatrically ill volunteers could also participate, but their records were not analyzed as per the pre-specified study protocol [ 18 ].…”

“…One probiotic dose was considered equivalent to 100 g of fermented food [ 31 , 32 ]. Fermented food equivalents of probiotic preparations were added to the total mass of six fermented food categories consumed throughout the seven days of dietary recording [ 17 ]—this total measure constituted the predictor in the analyses.…”

“…Details regarding the study procedure and research instruments are provided in our primary study report [ 17 ].…”