The gut microbiome has been implicated in skeletal, metabolic and inflammatory changes following menopause, yet the gut microbiome of healthy women in early postmenopause remains poorly characterised.1,2 Characterising the microbiome during this period may identify population-specific patterns and factors associated with microbial variation. This cross-sectional study characterised baseline gut microbiota composition and diversity in healthy early postmenopausal women enrolled in a longitudinal probiotic trial,3 and examined associations with demographic, anthropometric, skeletal, dietary and lifestyle characteristics.
Baseline stool samples from 100 women were analysed using full length 16S rRNA sequencing. Alpha diversity was assessed using Shannon diversity, observed ASV richness, Faith’s phylogenetic diversity and Pielou’s evenness. Associations with categorical baseline characteristics were examined using Wilcoxon rank-sum or Kruskal–Wallis tests, with Dunn’s post-hoc tests where appropriate; continuous traits were assessed using Spearman correlations. Beta diversity was assessed using Bray–Curtis, Jaccard, and weighted and unweighted UniFrac distances, with differences in community composition tested by PERMANOVA. Community profiles were identified using Dirichlet multinomial mixture modelling (DMM). P-values were adjusted for multiple comparisons using the Benjamini–Hochberg false discovery rate procedure.
At the phylum level, the microbiome was dominated by Firmicutes_A (63.1%), Firmicutes (19.6%) and Bacteroidota (10.6%). At the genus level, Blautia_A and Faecalibacterium had mean relative abundances of 10.9% and 8.5%, respectively; Faecalibacterium was highly variable between participants (median 6.92%, IQR 0.98–15.13%). DMM modelling identified two community types. DMM1 was characterised by enrichment of Faecalibacterium (63%) and several co-occurring taxa, including Oscillospiraceae, Blautia_A and Lachnospiraceae, while DMM2 was characterised by Blautia_A (37%) dominance and relative depletion of Faecalibacterium.No baseline characteristic was associated with community profile membership after BH correction. Women in the middle and highest dietary fibre intake tertiles had significantly greater Shannon diversity, observed richness and evenness than those in the lowest tertile (all adjusted p ≤ 0.014), while Faith’s phylogenetic diversity was higher in the highest tertile (adjusted p = 0.025). Women meeting physical activity guidelines (>150 min/week of moderate-to-vigorous activity) had greater observed richness (adjusted p=0.011). No significant between-group differences in beta diversity were detected after false discovery rate correction.
This study provides a baseline characterisation of the gut microbiome in healthy early postmenopausal women. Among the factors examined, dietary fibre intake showed the most consistent associations with microbial diversity, while physical activity was associated only with microbial richness. In contrast, overall community composition did not differ across the baseline characteristics examined, highlighting fibre as the most consistent lifestyle correlate of microbial diversity in this cohort.