The impact of a prebiotic-rich diet and/or probiotic supplements on human cognition: Secondary outcomes from the ‘Gut Feelings’ randomised controlled trial

BACKGROUND: Emerging evidence indicates that gut microbiota-targeted interventions may lead to improvements in cognition. We assessed whether a prebiotic-rich dietary intervention, probiotic supplement, or synbiotic combination of both would improve human cognition, as part of the 'Gut Feelings' trial. METHODS: An 8-week, 2 × 2 factorial randomised controlled trial was conducted on 118 adults with low mood and potential for dietary improvement. Treatment arms: (1) probiotic supplement and diet-as-usual (probiotic group); (2) high-prebiotic diet and placebo supplement (prebiotic diet group); (3) probiotic supplement and high-prebiotic diet (synbiotic group); and (4) placebo supplement and diet-as-usual (placebo group). At baseline and 8-weeks, the Cogstate Brief Battery was administered, testing processing speed, attention, visual learning, and working memory. Data were analysed using Bayesian linear regression. RESULTS: = 0.25, 95% CI: -0.02, 0.51; post. prob of harm: 97%). There was little indication of a synergistic interaction between the probiotic and prebiotic diet. CONCLUSION: Australian New Zealand Clinical Trials Registry (ACTRN12617000795392; registered 31 May 2017).