Prebiotic Consumption Alters Microbiota but Not Biological Markers of Stress and Inflammation or Mental Health Symptoms in Healthy Adults: A Randomized, Controlled, Crossover Trial

Background: Chronic stress contributes to systemic inflammation and diminished mental health. Although animal work suggests strong links with the microbiota-gut-brain axis, clinical trials investigating the effectiveness of prebiotics in improving mental health and reducing inflammation are lacking.Objectives: We aimed to determine fructooligosaccharide (FOS) and galactooligosaccharide (GOS) effects on biological markers of stress and inflammation and mental health symptoms in adults. Secondary outcomes included fecal microbiota and metabolites, digestive func-tion, emotion, and sleep.Methods: Twenty-four healthy adults (25-45 y; 14 females, 10 males; BMI, 29.3 +/- 1.8 kg/m2) from central Illinois participated in a 2 -period, randomized, controlled, single-blinded crossover trial. Interventions included the prebiotic (PRE) treatment (237 mL/d Lactaid low-fat 1% milk, 5 g/d FOS, 5 g/d GOS) and control (CON) (237 mL/d Lactaid), which were consumed in counterbalanced order for 4 wk each, separated by >= 4-wk washout. Inflammatory markers were measured in blood plasma (>10-h fast) and cortisol in urine. The Depression Anxiety Stress Scales-42 assessed mental health symptoms. Fecal samples were collected for 16S rRNA gene (V4 region) sequencing and analysis. Emotion was measured by rating images from a computer task. Sleep was assessed using 7-d records and accel-erometers. Change scores were analyzed using linear mixed models with treatment and baseline covariate as fixed effects and participant ID as the random effect.Results: There were no differences in change scores between PRE and CON treatments on biological markers of stress and inflammation or mental health. PRE increased change in percent sequences (q = 0.01) of Actinobacteriota (CON: 0.46 +/- 0.70%; PRE: 5.40 +/- 1.67%) and Bifidobacterium (CON:-1.72 +/- 0.43%; PRE: 4.92 +/- 1.53%). There were also no differences in change scores between treatments for mi-crobial metabolites, digestive function, emotion, or sleep quality.Conclusions: FOS+GOS did not affect biological markers of stress and inflammation or mental health symptoms in healthy adults; however, it increased Bifidobacterium.Clinical Trial Registry: NCT04551937, www.clinicaltrials.gov

Automated summary

This study found that prebiotic treatment (FOS+GOS) did not affect mental health and inflammation in healthy adults, but it increased the abundance of Bifidobacterium.