Gut metabolites linked to preserved brain thickness in older adults
In a 104-person trial sub-study, rising levels of gut-produced urolithins tracked with preserved cortical thickness over two years in 55 older adults eating walnuts.
Food & Function
In a longitudinal sub-study of a randomised controlled trial, researchers analysed 104 cognitively healthy older adults in Barcelona, Spain. The parent trial tested daily walnut consumption against a control diet for two years. Participants underwent structural brain scans and urine tests at baseline and after two years. The researchers related changes in urolithins, gut-microbiota metabolites of walnut compounds, to concurrent changes in cortical thickness, a marker of age-related neurodegeneration. Among 55 participants allocated to the walnut diet, greater increases in urolithin A, urolithin C, and its glucuronide conjugate were associated longitudinally with preservation of cortical thickness, predominantly in right-hemisphere regions. These associations were more pronounced in individuals with urolithin metabotype B.
Why it matters
The results provide clinical evidence linking gut-derived polyphenol metabolites to brain aging, bearing on how differences in individual gut metabolism might guide dietary strategies against age-related neurodegeneration.
Caveats
The analysis examined longitudinal associations within a trial sub-study rather than proving that urolithins caused the preservation of cortical thickness. The observed links were also restricted to a subset of 55 participants assigned to the walnut diet.
The paper
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Carola Pozzoli, Anna Vallverdú-Queralt, Mercè Serra-Mir, Gemma Chiva-Blanch, Sujatha Rajaram, Joan Sabaté, Aleix Sala-Vila, Emilio Ros,Universitat de Barcelona (UB)
Food & Function · 7 Oct 2026
