Abstract
Background.
Galacto–oligosaccharides (GOS) are prebiotics linked to gut microbiota modulation and potential gut–brain axis effects on neurochemistry, mental health and cognition. This study evaluated the influence of GOS along the gut–brain axis, integrating assessments of mental health, neurochemistry, gut microbiome composition, cognition, and nutrition in healthy females.
Methods.
In a randomised, double–blind, placebo–controlled trial, 83 females (17–25 years) received GOS or placebo for 28 days. Assessments occurred at baseline, endline, and 28 days post–supplementation. The primary outcome was trait anxiety, with secondary outcomes including neurochemical measures of GABA and glutamate via 1H–MRS in the dorsolateral prefrontal cortex (dlPFC), anterior cingulate cortex (ACC), and inferior occipital gyrus (IOG) of the brain, and gut microbiome composition. Tertiary outcomes included social anxiety, depression, emotion behaviour, reaction times, and nutritional intake. Analyses included intention–to–treat, per–protocol, and sensitivity approaches.
Results.
Trait anxiety did not differ significantly between groups at endline (p = .443), though trends favoured lower anxiety in the GOS group at follow–up (p = .069). GOS reduced GABA at trend significance in the inferior occipital gyrus (p = .053) and dorsolateral prefrontal cortex (p = .088) in high–anxious participants, with effects persisting at follow–up. GOS increased Bifidobacterium abundance (p = .001) but did not affect overall microbiome diversity. Tertiary outcomes showed no significant changes in social anxiety or depression but faster reaction rates in high–anxious participants for simple (p = .036) and choice tasks (p < .001). Nutritional intake was unaffected.
Conclusion.
While GOS supplementation did not significantly reduce trait anxiety, it produced neurochemical changes and transient modulations of the gut microbiome in Bifidobacterium abundance. These findings suggest GOS induced changes can be traced along the gut–brain axis, with implications for mental health and cognitive function that warrant further investigation.