Gut Microbiota Mediates Dietary Modulation of Mild Cognitive Impairment in the Elderly: A Cross-Sectional Study

Background Prospective studies investigating the relationship between dietary factors and cognitive function in elderly Chinese populations remain limited. And the role of gut microbiota in this relationship is unclear. In this study, we aimed to explore the role of gut microbiota in the dietary modulation on mild cognitive impairment (MCI). Methods This study enrolled 48 patients with MCI and 43 age-matched healthy controls (HC). Participant demographics and blood lipid levels were recorded. Dietary habits were assessed using a food frequency questionnaire (FFQ), and cognitive function was evaluated with the Montreal Cognitive Assessment (MoCA). Fecal samples were collected for 16S rRNA gene sequencing. Spearman’s correlation analysis was employed to examine correlations between gut microbiota and dietary intake, cognitive function, and low-density lipoprotein cholesterol (LDL-C). Results Compared to HC, MCI subjects had significantly lower education levels and higher serum total cholesterol (TC) and LDL-C levels ( P  < 0.05). The MCI group also exhibited significantly reduced consumption of bean curd/tofu pudding, yogurt, freshwater fish, shrimp and crab, pine nuts, and pumpkin ( P  < 0.05). Significant enrichment of the genera Desulfovibrio , Sutterella , UCG-003, norank_f__norank_o__RF39 , UCG-002, F0332 , Phocea , norank_f__norank_o__Elsterales , and Bryobacte was observed in the MCI group. Conversely, Actinomyces , Atopobium , Eubacterium_eligens_group , Ruminococcus_gnavus_group , and Streptococcus were significantly decreased in MCI subjects ( P  < 0.05). Spearman’s correlation analysis revealed significant positive associations between cognitive scores and the intake of yogurt, freshwater fish, shrimp and crab, and pine nuts ( P  < 0.05). Furthermore, Actinomyces and Streptococcus abundance correlated positively not only with the intake of freshwater fish and yogurt but also with cognitive performance. Conversely, UCG-003 and Desulfovibrio abundance correlated negatively with the intake of shrimp and crab, yogurt, as well as with cognitive scores. Additionally, serum LDL-C levels correlated negatively with yogurt intake and cognitive scores. Conclusions In conclusion, intake of yogurt, freshwater fish, and shrimp and crab was positively associated with cognitive performance. Gut microbiota composition, particularly enrichment of Actinomyces and Streptococcus , may mediate the beneficial cognitive effects of these dietary components. Conversely, UCG-003 and Desulfovibrio may exert detrimental effects on cognition. Notably, serum LDL-C levels may represent a mediating factor in the diet-cognition relationship.