Abstract

Background: Prospective studies investigating the relationships between dietary factors and cognitive function in elderly Chinese individuals are limited. The role of the gut microbiota in this relationship is unclear. Here, we aimed to explore the role of the gut microbiota in dietary modulation of mild cognitive impairment (MCI).

Methods: This study included 48 patients with MCI and 43 age-matched healthy controls (HCs). 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). Faecal samples were collected for 16S rRNA gene sequencing. Spearman’s correlation analysis was used to examine correlations between the gut microbiota and dietary intake, cognitive function, and low-density lipoprotein cholesterol (LDL-C) levels.

Results: Compared with HCs, subjects with MCI 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, crustaceans (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, the abundance of Actinomyces , Atopobium , Eubacterium_eligens_group , Ruminococcus_gnavus_group , and Streptococcus was significantly decreased in the MCI group ( P < 0.05). Spearman's correlation analysis revealed significant positive associations between cognitive scores and intake of yogurt, freshwater fish, crustaceans, and pine nuts ( P < 0.05). Furthermore, the abundance of Actinomyces and Streptococcus correlated positively not only with intake of freshwater fish and yogurt but also with cognitive performance. Conversely, UCG-003 and Desulfovibrio abundance correlated negatively with intake of crustaceans and yogurt and 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 crustaceans was positively associated with cognitive performance. Changes in the composition of the gut microbiota, particularly enrichment of Actinomyces and Streptococcus , may mediate the beneficial cognitive effects of these dietary components. Conversely, UCG-003and Desulfovibrio may exert detrimental effects on cognition. Notably, serum LDL-C levels may represent a mediating factor in the relationship between diet and cognition.