The impact of estrogen status on the gut microbiome: a systematic review and meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational comparative studies
PubMed 42006274 · doi:10.3389/fendo.2026.1780806
What was done
Authors conducted a systematic review and meta-analysis of studies indexed in PubMed, SCOPUS, and Embase through December 2024. The review evaluated gut microbiome alterations in hypoestrogenic women (post-menopausal or with premature ovarian insufficiency) compared to euestrogenic pre-menopausal controls. The primary outcome was alpha-diversity measured by the Shannon index. Secondary outcomes were the relative abundances of Bacteroidetes, Firmicutes, and the Bacteroidetes-to-Firmicutes ratio, synthesized using random-effects models.
What was found
Across 7 included studies (45 women with premature ovarian insufficiency, 1,222 post-menopausal women, and 463 controls), no statistically significant differences were detected between hypoestrogenic and euestrogenic groups for alpha-diversity (p = 0.990), Bacteroidetes relative abundance (p = 0.440), Firmicutes relative abundance (p = 0.110), or the Bacteroidetes-to-Firmicutes ratio (p = 0.400). Between-study heterogeneity was high across outcomes (I² ranging from 61% to 99%).
Why it matters
Despite frequent mechanistic claims that estrogen decline reshapes the gut microbiota, aggregated human observational evidence does not show consistent differences in overall diversity or dominant bacterial phyla.
Limits
The analysis relies on a small number of observational studies (7 studies, with only 45 patients representing premature ovarian insufficiency). Between-study heterogeneity was substantial (I² up to 99%), methodological quality varied across studies, and primary studies had limited control for major microbiome confounders such as diet, age, medication use, and metabolic status.
Cited by
- contradicts Falling estrogen levels in women cause a reduction in gut microbial diversity.