Influence of diet on the modulation of gut microbiota and its neurobiological effects on cognition: a systematic review and meta-analysis

Abstract

Introduction: The gut microbiota, a key regulator of the gut-brain axis, is profoundly influenced by diet, and its modulation through dietary patterns may play a critical role in mitigating mild cognitive impairment (MCI).

Objective: To evaluate whether dietary interventions modify gut microbiota composition in individuals with MCI and to determine whether these microbiota changes are associated with variations in cognitive function.

Methods: A systematic review and meta-analysis were conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Randomized clinical trials and observational studies evaluating dietary exposures, gut microbiota, and cognitive outcomes in adults with MCI were included. Data extraction and risk-of-bias assessment were performed using standardized and validated tools. When applicable, pooled effects on cognition were estimated using random-effects models and between-study heterogeneity was quantified.

Results: Of 3,029 records identified, 11 studies met the inclusion criteria (nine randomized trials and two observational studies), with a weighted mean age of 65.24 years. Gut microbiota differed between normal cognition and MCI-beneficial taxa (e.g. Bifidobacterium, Faecalibacterium) predominated in normal cognition, while potentially taxa more frequently reported in pro-inflammatory/dysbiosis-associated profiles (e.g. Ruminococcus, Enterobacteriaceae) were higher in MCI. The pooled effect showed a trend favoring dietary interventions (standardized mean difference = −0.32 (95% CI: −0.92 to 0.28)), although this did not reach statistical significance.

Conclusion: This review highlights the potential role of diet in modulating gut microbiota and its impact on cognition in MCI, emphasizing the need for standardized interventions and further research to clarify the underlying mechanisms.