Effects of a high-prebiotic diet versus probiotic supplements versus synbiotics on adult mental health: The “Gut Feelings” randomised controlled trial Original paper

What was studied?

This study focused on assessing the effects of different interventions on mental health, specifically comparing a high-prebiotic diet, probiotic supplementation, and a combination of both (synbiotics). The research aimed to determine whether these interventions could improve mental health outcomes, including mood, anxiety, stress, and sleep, in adults with moderate psychological distress and low prebiotic intake. The study was conducted over 8 weeks and evaluated various psychological symptoms using validated scales.

Who was studied?

The study involved 119 adults with moderate psychological distress and low prebiotic intake. Participants were randomly assigned to four groups: (1) probiotic supplementation with diet-as-usual, (2) a high-prebiotic diet with a placebo supplement, (3) a combination of both probiotics and the high-prebiotic diet (synbiotics), and (4) a placebo group with diet-as-usual. All participants were assessed for mental health symptoms such as mood disturbance, anxiety, stress, and sleep before and after the 8-week intervention.

What were the most important findings?

The study found that a high-prebiotic diet significantly reduced total mood disturbance (TMD) compared to the placebo group, showing a moderate effect size (Cohen’s d = −0.60). Participants in the prebiotic diet group also experienced improvements in anxiety, perceived stress, and sleep quality. However, no significant improvements were observed in the probiotic or synbiotic groups. The synbiotic combination did not outperform the prebiotic diet alone, with some evidence suggesting an antagonistic interaction between the prebiotic diet and probiotic treatment, leading to poorer outcomes in the synbiotic group. Overall, the study suggests that a high-prebiotic diet can have beneficial effects on mood and anxiety, but the combined synbiotic treatment did not show a significant added benefit.

What are the implications of this study?

The greatest implication of this study is that dietary interventions, specifically high-prebiotic diets, could be a promising and non-pharmacological strategy to improve mental health, particularly for individuals with moderate psychological distress. This approach may offer a sustainable, low-risk method to manage mood disturbances, anxiety, and stress. The results also suggest that prebiotic-rich diets could be used to modulate the gut microbiota in ways that influence psychological well-being, further supporting the growing body of evidence linking gut health to mental health. However, the lack of efficacy in the synbiotic group highlights the need for further research into the synergistic effects of combining prebiotics and probiotics, as the results did not align with the anticipated benefits.