# Gut enterotype- and body mass index (BMI)-dependent effects of anthocyanin supplementation on gut microbiota composition in individuals at risk for cognitive decline: a randomized placebo-controlled trial

## TL;DR

This study shows that anthocyanin supplements affect gut bacteria differently depending on a person's gut type and BMI, but not cognitive performance.

## Contribution

The study reveals that anthocyanin effects on gut microbiota are influenced by enterotype and BMI, supporting personalized nutrition strategies.

## Key findings

- Anthocyanin supplementation caused BMI-specific changes in gut bacteria, such as Oscillibacter in healthy-weight individuals and Bacteroidota in obese participants.
- Baseline enterotype determined the direction and consistency of microbiota shifts, with enterotype one showing modest changes and enterotype two showing broader but less coherent changes.
- Age-related differences showed quartile-specific modulations in gut microbiota, but no significant impact on cognitive performance.

## Abstract

Anthocyanins, bioactive flavonoids found in berries, modulate gut microbiota composition and influence health outcomes. This study investigated the effects of anthocyanin supplementation on gut microbiota and cognition in older adults (60–80 y) at risk of cognitive decline due to mild cognitive impairment (MCI) or cardiometabolic disorders (CMD). In a 24-week, randomised, double-blind, placebo-controlled trial (n = 99), participants received anthocyanin capsules or placebo. Gut microbiota composition was profiled using 16S rRNA sequencing, considering factors such as baseline enterotype, body mass index (BMI), and age. Overall, alpha diversity remained unchanged, while beta diversity indicated modest but significant intervention effects at the amplicon sequence variants level. Baseline enterotype strongly influenced responsiveness: enterotype one (higher diversity, eubiotic taxa) showed modest but consistent shifts, whereas enterotype two (dysbiotic, Bact2-like) exhibited broader but less coherent changes. BMI-specific responses included enrichment of Oscillibacter and Ezakiella in healthy-weight individuals and Bacteroidota taxa in obese participants, alongside consistent reductions in Firmicutes. Age stratification revealed heterogeneous, quartile-specific taxa modulations. Cognitive performance, measured by episodic memory, was unaffected, and microbial shifts did not mediate intervention effects. These findings demonstrate that anthocyanins selectively modulate the gut microbiome in an age-, BMI-, and enterotype-dependent manner, underscoring the importance of personalized microbiome-informed nutritional interventions.