Menopause and Your Gut Microbiome: What Happens?
Throughout history, medical research has primarily focused on males, resulting in significant gaps in research related to women's health.
Despite the fact that approximately half of the global population will experience menopause, many individuals lack adequate information about what to expect.
Therefore, addressing inquiries about menopause is more important now than ever before.
Scientists, including those at ZOE, are beginning to gain a better understanding of menopause, but there is a pressing need for more research in this area.
Gut Bacteria and Menopause
Research has shown that a healthy and diverse gut microbiome is linked to various aspects of overall health.
In this context, we will explore how the composition of your gut microbiome changes during menopause and how these changes may impact disease risk and symptoms during this transitional period.
However, due to the lack of extensive research on menopause and the early stage of gut microbiome science, the available evidence is limited.
With that in mind, let's delve deeper into this topic.
Your Microbiome Over Time
Throughout your life, the composition of your gut microbiome undergoes changes. One significant shift occurs in early childhood when transitioning from milk to solid food.
Another crucial change occurs during adolescence when the gut microbiome of females, but not males, becomes more similar to that of adults.
Hormonal differences may contribute to the variations in the gut microbiomes of men and women during adulthood.
Upon reaching menopause, which occurs one year after the last menstrual period, the production of sex hormones such as progesterone and estrogen by the ovaries ceases.
Given that sex hormones influence gut bacteria and hormonal levels fluctuate during menopause, it is logical to assume that changes in the gut microbiome may occur during this period.
The decline in estrogen levels, in particular, contributes to many of the symptoms associated with menopause, including hot flashes, night sweats, vaginal dryness, and mood changes.
Estrogen reduction also leads to an increased risk of certain health conditions such as heart disease and osteoporosis.
During the menopausal transition and beyond, some individuals opt for hormone replacement therapy (HRT) to elevate sex hormone levels and alleviate symptoms and disease risk.
So, how do gut bacteria impact sex hormone levels?
Gut Microbes and Sex Hormones
As mentioned earlier, sex hormones appear to influence the diversity of your gut microbiome.
However, the relationship between gut bacteria and hormones is reciprocal.
Gut bacteria also play a role in regulating the levels of hormones in your bloodstream. To understand this process, we need to delve into the details.
The primary estrogens in your body are estrone, estriol, and estradiol. Once they reach the liver, they undergo metabolism.
During this metabolic process, they bind irreversibly to other compounds, preventing them from exerting their normal effects on the body's cells and tissues.
Subsequently, these bound compounds are excreted through the gut. In essence, the liver eliminates them from the bloodstream.
However, certain bacteria in your gut can "recycle" estrogens. These bacteria have the ability to detach the compounds from estrogens, allowing them to re-enter the bloodstream.
A similar process occurs with other hormones, including progesterone and androgens like testosterone.
Therefore, it appears that hormones contribute to the nourishment of specific gut bacteria. In return, gut bacteria facilitate the re-entry of these hormones into the bloodstream for reuse.
Fascinating Research
Although research on the gut microbiome and hormone levels is limited, some studies have yielded intriguing results.
For instance, a meticulously conducted study in Austria involved 16 women using hormonal contraceptives, which typically reduce estradiol and progesterone levels.
A diverse gut microbiome is generally indicative of good gut health. The researchers found that decreases in these hormones were associated with lower gut microbiome diversity.
Furthermore, there were alterations in the relative abundance of certain types of bacteria.
For example, hormonal contraceptives were linked to reduced numbers of Eubacterium, some of which are considered beneficial gut bacteria, such as E. eligens.
The study also demonstrated fluctuations in bacterial levels throughout the participants' menstrual cycles, further highlighting the influence of hormones on gut bacteria.
During Menopause
Overall, the evidence suggests that the interplay between hormones and gut bacteria operates in the following manner: Higher estrogen and progesterone levels enhance gut bacteria diversity by providing nourishment.
Conversely, increased gut bacteria diversity results in more hormones being recycled and re-entering circulation.
Postmenopausal women experience significantly low levels of estrogens and progesterone. As a result, the recycling process by gut bacteria may play a crucial role in determining the hormone levels in their blood.
Additionally, there are other potential interactions between sex hormones and gut bacteria.
Understanding Translocation
Maintaining a thriving population of gut bacteria is beneficial. However, if these microbes or their byproducts enter the bloodstream, it can have negative consequences, a phenomenon known as translocation.
To prevent translocation, the gut lining has various defense mechanisms in place. The intestinal epithelium, a thin layer of cells lining the intestines, plays a key role in this defense.
However, there are instances where these protective barriers are breached, allowing gut bacteria or their products to translocate.
When translocation occurs, it can lead to inflammation, which is associated with a range of health conditions, including heart disease, cancer, and diabetes.
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Some evidence, primarily from animal and laboratory studies, suggests that sex hormones play a role in maintaining gut barrier integrity.
For example, a laboratory study demonstrated that estradiol protects mucus-producing cells in the intestinal epithelium from damage. Additionally, research involving rats and human tissue indicated that activating estrogen receptors helped reduce translocation.
While there is limited direct evidence linking menopause to gut barrier integrity, some studies suggest that microbial translocation from the intestines may occur more frequently during menopause.
At present, the extent to which translocation influences symptoms and disease risk during menopause remains unclear, underscoring the need for further research in this area.
A Role in Bone Health?
In addition to the recycling of estrogen by gut bacteria and the potential impact on translocation, the relationship between gut bacteria and menopause extends to bone health.
As estrogen levels decline, the risk of developing osteoporosis, a condition characterized by weakened bones and increased fracture risk, rises.
Surprisingly, gut bacteria contribute to maintaining optimal bone health.
Preliminary research indicates that manipulating the gut microbiome with probiotics may help preserve bone strength.
Exploring Isoflavones
Certain plants contain phytoestrogens, including isoflavones found in soy.
Some gut bacteria have the ability to convert isoflavones into estrogen-like compounds that can bind to estrogen receptors, mimicking estrogen's actions.
However, the relationship becomes more complex when estrogen levels are high, as these estrogen-like compounds seem to inhibit estrogen's effects.
Conversely, when estrogen levels are low, as during the menopause transition and beyond, these compounds mimic estrogen's actions.
Research suggests that consuming soy isoflavones may help reduce the risk of certain menopausal symptoms, such as hot flashes, by replicating estrogen's effects.
Therefore, gut bacteria may play a role in restoring some of the functions associated with sex hormones in individuals experiencing menopause.
Changes in the Gut Microbiome
While we have explored how gut bacteria can influence sex hormone levels, it is essential to understand the specific alterations that occur in the gut microbiome during menopause.
Only a limited number of studies have investigated this question, with most being relatively small and yielding mixed results.
To interpret these findings, a review conducted in April 2022 analyzed ten studies focusing on menopause, sex hormones, and gut bacteria.
Among these studies, five revealed a decrease in gut bacteria diversity following menopause or in women with low estrogen levels.
Furthermore, three of the ten studies found that the gut microbiomes of postmenopausal women were more akin to those of men than premenopausal women.
Some studies also reported changes in the abundance of specific gut bacteria. For instance, individuals tended to have lower levels of Firmicutes and Ruminococcus post-menopause.
Conversely, they exhibited higher levels of Butyricimonas, Dorea, Prevotella, Sutterella, and Bacteroides.
While the implications of these changes for health remain unclear, some insights can be gleaned.
For example, Ruminococci ferment fiber in the gut and produce short-chain fatty acids (SCFAs), which offer various health benefits. Therefore, a decrease in these bacteria may have negative consequences.
Moreover, as noted by the review authors, "Dorea, Prevotella, and Sutterella have all been linked to obesity in multiple studies." Hence, an increase in these bacteria may have adverse effects on health.
However, the impact of Prevotella on health is still subject to debate. The relationship between individual gut bacteria and health outcomes remains inadequately understood.
In November 2022, ZOE scientists published one of the largest studies to date focusing on gut bacteria during menopause.
Utilizing data from over 1,000 women as part of the PREDICT 1 study, our researchers observed increased levels of bacteria associated with inflammation and obesity in postmenopausal women.
Does Hormone Replacement Therapy Revert the Changes?
You may be curious about whether hormone replacement therapy (HRT), which elevates sex hormone levels, can reverse these alterations.
Unfortunately, there is limited research on this topic. However, a study offers some insights. Researchers recruited females under 40 whose ovaries had ceased hormone production.
These individuals exhibited notably high levels of Eggerthella compared to healthy participants. The researchers suggest that Eggerthella may be associated with widespread inflammation.
Upon receiving estradiol hormone therapy, the levels of Eggerthella decreased. However, since the participants were not postmenopausal, and the study focused on a single bacterium, the influence of HRT on the gut microbiome remains uncertain.
Concluding Thoughts
The current evidence indicates that menopause affects the gut microbiome, but the implications for health remain unclear.
While hormones appear to directly influence these changes, other factors may also be significant.
For instance, as outlined by researchers in a review, progesterone impacts the immune system and the rate of food passage through the gut.
With lower progesterone levels, alterations in the immune system and gut transit time may contribute to changes in the gut microbiome.
Therefore, extensive research on menopause is essential. In the meantime, individuals can take steps to support their gut microbiome regardless of their life stage. For personalized advice on enhancing gut health and understanding your gut bacteria profile, ZOE offers valuable resources.
If you are curious about the composition of bacteria in your gut, consider taking our free quiz today.
