Researchers conducted a systematic review and meta-analysis to see if women with low estrogen levels have different gut bacteria compared to women with normal estrogen levels. They combined data from 45 women with premature ovarian insufficiency, 1,222 post-menopausal women, and 463 pre-menopausal women with normal estrogen levels. The goal was to understand if hormonal changes affect the gut microbiome.
The analysis found no significant differences in the overall diversity of gut bacteria or in the relative amounts of two major bacterial groups, Bacteroidetes and Firmicutes, between the groups. The ratio of these two bacterial types also showed no clear difference. All comparisons showed no statistically significant results.
It is important to be careful with these results because the individual studies included in this review were very different from each other, a problem known as high heterogeneity. The studies also had limited control for other factors that affect gut bacteria, like diet and lifestyle, and varied in their scientific quality. This means the finding of 'no difference' may not be definitive.
Readers should understand that this large review of existing evidence does not support the idea that low estrogen consistently changes the gut microbiome in a specific way. More carefully controlled research is needed to answer this question with greater certainty.