Anxiolytic effects of a prebiotic in healthy female volunteers are associated with reduced negative bias and increased beneficial gut bacteria.

The main aim of the current study was to investigate whether prebiotic intake influences anxiety and mood measures in late adolescence and early adulthood in humans. This developmental stage undergoes refinement by maturation of emotional regulation networks that are influenced by social, biological and cognitive factors and is characterised by ongoing brain development. Specifically, we compared the effects of a 4-week course of prebiotic intake compared to a placebo on the gut-microbiome and emotional behaviour and well-being. Emotional behaviour (as assessed with the attentional dot-probe task and a number of self-report measures on anxiety and depression) was chosen as a model as evidence has shown that good emotion processing abilities in development are linked with various indices of well-being and mental health. In the current study we hypothesised that a daily intake of a prebiotic galacto-oligosaccharides (GOS) for 4 weeks would: 1) reduce self-reported levels of anxiety in the GOS group in comparison to the placebo group; 2) improve attentional bias towards positive emotional stimuli in the dot-probe task, and 3) stimulate the outgrowth and/or activity of potently beneficial gut bacteria (such as Bifidobacterium) in the GOS compared to the placebo group.