Nut consumption, gut microbiota, and cognitive function: findings from a prospective study in older adults at risk of cognitive decline

BACKGROUND: The diet-microbiota-gut-brain axis emerges as a promising target for preventing neurodegenerative disorders. Nuts are nutrient-dense foods with potential neuroprotective and prebiotic properties, yet their relationship with longitudinal cognitive changes and gut microbiota remains unclear. OBJECTIVE: To assess the association of baseline nut consumption with 6-year changes in cognitive function and baseline gut microbiota composition in older adults. METHODS: This prospective study included 747 participants (mean age 65 ± 5 years, 48% women) with overweight/obesity and metabolic syndrome. Baseline nut consumption, assessed via a validated food frequency questionnaire, was categorised as ≤1, 1-3, 3-7, and > 7 servings/week. Cognitive function was evaluated at baseline and at 2, 4, and 6 years, using a comprehensive battery of neuropsychological tests. Gut microbiota composition was profiled through 16S rRNA amplicon sequencing. Multivariable linear mixed-effects and linear regression models were utilized. RESULTS: Participants consuming 3-7 servings of nuts/week showed significantly slower declines in global cognitive function over the follow-up period compared to those consuming ≤1 serving/week (4-year: β[95%CI] = 0.170[0.022,0.319], P = .024; 6-year: 0.176[0.020,0.331], P = .027). This nut consumption category was also associated with higher gut microbial diversity (Shannon index: β[95%CI] = 0.211[0.008,0.414], P = .042). Thirteen taxa were associated with nut consumption, 10 positively, including Lachnospiraceae UCG-004, which was further associated with positive changes in global cognitive function (2-year: β[95%CI] = 0.020[0.004,0.036], q = 0.050) and slower decline in attention (6-year: 0.042[0.020,0.064], q = 0.001). CONCLUSIONS: Moderate nut consumption (3-7 servings/week), was interconnectedly associated with cognitive preservation and favourable gut microbiota composition, underscoring the potential of dietary modulation of the gut-brain axis for healthy ageing.