What does the transition into menopause do to your gut microbiome?
Menopause noticeably changes your gut microbiome: less diversity, weaker reactivation of oestrogen and a slightly more permeable gut wall. Fibre and probiotics can help, but discuss hormone therapy with your doctor if you have more pronounced symptoms.
The menopause brings a significant drop in oestrogen, and that drop affects your gut bacteria too. After menopause, the diversity of the gut microbiome decreases: fewer different bacterial species are present. In one summary analysis of three small studies this difference was not statistically significant, so the picture is not yet fully clear. However, at the level of specific bacterial strains there are clear shifts: some bacteria occur more frequently after menopause, while others occur less.
An important mechanism behind this interaction is an enzyme in your gut bacteria that makes oestrogen reactivatable by the body. After menopause this enzyme is less active, causing circulating oestrogen levels to fall even further. That lower level in turn changes the composition of the microbiome, which then produces even less of this enzyme: a self-reinforcing cycle.
A second consequence is that the gut wall appears to become more permeable after menopause. Bacteria and their waste products can then enter the bloodstream more easily, which can fuel a smouldering chronic inflammation. That may sound abstract, but this mechanism has been linked to bone loss, cardiovascular disease and other conditions that become more common in later life.
In a large study of more than 1,300 women, the altered gut microbiome after menopause was associated with less favourable blood sugar and lipid values. This is an association, not a proven cause and effect. It is also striking that the gut microbiome composition of postmenopausal women begins to resemble that of men, most likely because both groups have low oestrogen levels.
What can you do about this? Probiotics (such as Lactobacillus species) and prebiotic fibres can improve the diversity of the gut microbiome and appear to have a positive effect on metabolic health in women going through the menopause. The evidence is still limited and the best approach has not yet been established. Hormone therapy with oestrogen appears to be able to partially counteract the increased permeability of the gut wall, which could also offer bone protection. However, this has been studied in small studies, largely in women whose ovaries were surgically removed, so it does not automatically apply to everyone.
Based on observational studies, one meta-analysis of three small studies and one large association study (n>1,300). No large randomised trials. The causal relationships are plausible but not proven; most claims are associational or based on limited mechanistic research.