Four-Week Fermented Dairy Beverage Consumption Impacts Gut Microbiota and Improves Relational Memory

Abstract

Abstract Objectives Converging evidence suggests probiotic supplementation can reduce cognitive and metabolic concerns for persons with gastrointestinal disorders. However, in healthy populations the impact of probiotics on these outcomes is lacking. Thus, we aimed to determine whether symptoms of depression and anxiety, memory function, cortisol concentrations, and gut microbiota composition are altered by consumption of a fermented dairy beverage containing probiotic microorganisms in healthy adults. Methods Adults (25–45 yrs, N = 26) free of physician diagnosed gastrointestinal and mental illness were enrolled in a single-blind, randomized crossover trial. Participants completed testing prior to and after 4-week consumption, with a 2–4 week washout between treatments of kefir, a dairy-based fermented beverage containing 25–30 billion colony forming units of live and active kefir cultures (including 3 Bifidobacterium spp., 6 Lactobacillus spp., Streptococcus Diacetylacti., Luconostoc Cremoris, and Staccharomyces Florentinus) or isocaloric, non-fermented dairy-based control beverage. Hippocampal-dependent relational memory was assessed using a spatial reconstruction task. Symptoms of depression and anxiety were assessed using the depression anxiety and stress subscale (DASS). Pooled 24-hour urine samples were analyzed using an enzyme-linked immunosorbent assay to determine urinary-free cortisol (UFC) concentrations. Fecal microbiota composition was assessed using 16 s rDNA sequencing. Results Post-test logistic regression analysis revealed an increase in the number of participants with Lactobacillus spp. present (b = 3.00, P < 0.01) after consumption of kefir. Two-by-two repeated measure ANOVA displayed that the treatment improved performance on two metrics of relational memory (F[1, 25] = 4.54, P = 0.043, F[1, 25] = 5.50, P = 0.027). UFC and DASS scores were not significantly changed by either arm of the intervention. Conclusions These results reveal that kefir consumption increases the presence of probiotic microorganisms in the gut and improves relational memory in healthy adults. The impact of fermented dairy beverages containing probiotic microorganisms in healthy populations should be studied at a larger scale to better elucidate these outcomes. Funding Sources USDA National Institute of Food and Agriculture.