Short Oral Presentation Nutrition Society of Australia 50th Annual Scientific Meeting 2026

Baseline gut microbiome composition predicts cognitive response to anthocyanin-rich dietary interventions in older adults: An exploratory randomised controlled trial (143261)

Karen Charlton 1 , Jordan Stanford 1 , Xiao-Tao Jiang 2 , Vinicius do Rosario 3 , Karina Chan 4 , Henry Brodaty 4 , Kaarin Anstey 4 , Elnaz Lorzadeh 5 , Katherine Kent 5
  1. School of Health Sciences, University of Newcastle, Newcastle, NSW, Australia
  2. MRC, University of New South Wales, Sydney, NSW, Australia
  3. Institute for Evidence-Based Healthcare, Bond University, Robina, Queensland, Australia
  4. Neura, University of New South Wales, Sydney, NSW, Australia
  5. University of Wollongong, Wollongong, NSW, Australia

Background: Polyphenol-rich diets, including anthocyanin-containing foods, are associated with reduced cognitive decline in older adults1, potentially via modulation of the gut microbiome. However, it is unclear whether different anthocyanin sources produce comparable microbial effects or whether baseline microbiome composition influences cognitive responses.

Objective: To compare the effects of two anthocyanin delivery formats versus placebo on gut microbiome composition in older adults with subjective cognitive decline (SCD), and to explore whether baseline microbiome features predict cognitive outcomes.

Methods: This secondary analysis used data from a 6-month randomised, parallel, three-arm trial in adults with SCD.2 Participants were assigned to a whole-food “purple diet” (~250 mg anthocyanins/day via dietary counselling), blackcurrant powder (~250 mg/day), or a colour-matched placebo. Gut microbiome analyses were conducted in a subset of 54 participants (17 placebo, 20 purple diet, 17 blackcurrant) with paired baseline and 12-week shotgun metagenomic data and cognitive outcomes (Free and Cued Selective Reminding Test).

Results: Alpha diversity declined significantly in the placebo group (p < 0.05) but was maintained with both active treatments. The two interventions produced divergent microbiome responses: of 48 significantly different species (FDR < 0.05), most (n = 30) differed between the active treatments rather than versus placebo. The purple diet enriched Faecalibacterium and Bacteroides, while blackcurrant favoured Clostridium saudiense and other Firmicutes. No pathway-level differences were detected. Neither intervention improved cognition at the group level, although individual responses varied. Baseline microbial pathways, particularly fermentation and biosynthesis, predicted cognitive change in a treatment-dependent manner, suggesting that pre-existing microbial capacity may influence responsiveness to polyphenols.

Conclusion: Despite equivalent anthocyanin doses, whole-food and supplemental interventions produced distinct microbiome and cognitive patterns, indicating that delivery format matters. Baseline microbiome composition may help explain individual variation in cognitive response.

  1. 1. Lorzadeh E, Weston-Green K, Roodenrys S,et al. (2025). Curr Nutr Rep 14, 23.
  2. do Rosario V, Chan K, Lorzadeh E et al. (2026). Food Funct 17, 3400-3414.