What does the transition into menopause do to your gut microbiome?
Menopause noticeably changes your gut microbiome, although the effect is less dramatic than is sometimes suggested. The most concrete consequence is a disrupted cycle in which the gut microbiome and oestrogen pull each other downward; what you can practically do about that through diet or probiotics is still very much under investigation.
Menopause lowers oestrogen levels, and that has consequences for gut bacteria. The gut microbiome contains an enzyme that converts oestrogen into an active form so the body can reuse it. After menopause this enzyme is less active, causing oestrogen levels to fall even further. In this way the gut microbiome and hormones reinforce each other in a downward spiral.
At the level of individual bacterial species there are measurable shifts. The bacterium Akkermansia muciniphila, which protects the gut lining, decreases after menopause. Other species such as Bacteroides increase instead. One large study showed that the gut microbiome of post-menopausal women began to resemble that of men more closely. Yet these patterns are not the same in every study, and at the level of major bacterial groups there are barely any demonstrable menopause-specific changes.
Whether the diversity of the gut microbiome clearly declines after menopause is less certain than is often assumed. Large studies see a trend towards lower diversity, but in smaller studies that difference is not statistically significant. Part of what changes in the gut microbiome after menopause also appears to be simply associated with ageing in general, and not specifically with the hormonal change.
The gut lining does appear to become somewhat more permeable after menopause. This allows bacteria and their waste products to reach the bloodstream more easily. This promotes a smouldering, chronic inflammation in the body, which in turn may contribute to bone loss and a less favourable cardiovascular profile. This has partly been studied in women whose ovaries were surgically removed, not exclusively in women going through natural menopause.
Probiotics, such as Lactobacillus species, are being investigated as a means of supporting the gut microbiome in menopausal women. There are cautious indications that they can somewhat improve diversity and metabolism, but the evidence is still too thin for concrete recommendations. Which specific probiotic strains work, for which complaint and at which dose, has not yet been sufficiently studied.
Based on a combination of observational population studies, reviews and a meta-analysis of three smaller studies. Causal relationships are partly plausible but not yet fully proven. Much of the mechanistic evidence comes from studies in women who were brought into menopause surgically.