Investigating the Effects of Probiotics on Oestrogen-related Pathologies: A Systematic Review & Meta-Analysis

Background: Probiotics may enhance the effects of exogenous oestrogens such as hormone replacement therapy and isoflavones, and may lead to improvements in menopausal symptoms, and cardiovascular, bone and vaginal health. Objectives: To examine the effects of probiotics on oestrogen-related pathologies and explore whether probiotics influence the effects of exogenous oestrogenic substances. Search strategy: Searches of EMBASE, MEDLINE, Cochrane Library, Scopus, and Web of Science were performed. Selection criteria : Studies reported on the effects of probiotics, or probiotics plus oestrogenic substances such as estriol or isoflavones, among perimenopausal or recently postmenopausal women. Data collection & analysis: All findings were narratively synthesised; 7 studies were examined via meta-analysis which examined the effects of probiotics versus placebo. Main results: Thirty-nine studies contributed data from 3,187 women. Probiotics were associated with improvements in menopausal symptoms, urogenital conditions, bone health, and enhancements in the efficacy and safety of estriol and isoflavones. Meta analysis demonstrated large effects of probiotics on menopausal symptoms (total score): [standardised mean difference (SMD)= -0.82, (95% CI -0.52 to -1.09)], vasomotor symptoms: [SMD= -0.96, (95% CI -1.25 to -0.68)], psychological symptoms: [SMD=-0.51, (95% CI -0.95 to -0.08)], vaginal dryness: [SMD=-0.95 (95% CI -1.40 to -0.49)], and vaginal microbiome health (Nugent score): [SMD=-0.91 (95% CI -1.32 to -0.49)]. Meta analysis results were nonsignificant in relation to somatic and sexual symptoms. Conclusions: : Findings suggest that probiotics may improve conditions related to low oestrogen levels. Moreover, probiotics may enhance the effects of estriol and isoflavones. While findings are limited by the high risks of bias in the included studies, these results are promising and require further investigation.