Effects of non-pharmacological interventions on gut microbiota and intestinal permeability in older adults: A systematic review

This systematic review appraised previous findings of non-pharmacological interventions on gut microbiota and/ or intestinal permeability in older adults. A literature search was performed using PubMed, Scopus, ScienceDirect and the Cochrane Library. Relevant studies were shortlisted based on the inclusion and exclusion criteria, and evaluated for risks of bias using the “Cochrane Collaboration's Risk of Bias 2” and the “NIH Quality Assessment Tool for Before-After (Pre-Post) Studies with No Control Group”. The primary outcomes were the effects of non-pharmacological interventions on gut microbiota diversity and composition, and intestinal permeability in older adults. Out of 85,114 studies, 38 were shortlisted. Generally, the non-pharmacological interventions were beneficial against dysbiosis and the leaky gut in older adults. Considering specific interventions with two or more studies that reported consistent outcomes, a pattern was observed amongst the Mediterranean diet (MD), polyphenol-rich (PR) diet and supplements (i.e., probiotics, prebiotics and synbiotics). As for the other interventions, the very few studies that have been conducted did not allow a strong conclusion to be made just yet. The MD (single and multidomain interventions) restored gut microbiota by increasing species richness (alpha diversity) and reduced intestinal permeability (zonulin) and inflammation (CRP). The PR diet only showed slight changes in the gut microbiota but improved the gut barrier by reducing zonulin, CRP and IL-6. Probiotics, prebiotics and synbiotics increased the genus Bifidobacterium spp. which are considered beneficial bacteria. This review has uncovered insights into the relationship between gut microbiota and intestinal epithelial barriers of specific non-pharmacological interventions in older adults.