By Andrea McBeth, ND
The Microbiome-Fertility Connection: A Growing Concern
Fertility rates in the U.S. have steadily declined over the past several decades, with recent data reflecting some of the lowest birth rates on record. This decline - coincidentally or not so coincidentally - is happening alongside rising rates of chronic health conditions, such as obesity, autoimmune disorders, and metabolic syndromes, as well as hormonal imbalances like polycystic ovary syndrome (PCOS) and thyroid disorders. These conditions often play a role in infertility, impacting millions of people trying to conceive. I have often asked myself the question whether one of the most overlooked contributors to this crisis lies within the tiny organisms that make up our gut microbiome, and this blog explores that question. After all, the gut microbiome—home to trillions of bacteria, fungi, and other microorganisms—does much more than aid digestion and regulate immune function; it also plays a vital role in hormone balance and inflammation, two factors central to reproductive health.
Infertility is a deeply personal and complex issue, affecting about 1 in every 8 couples in the U.S. While the causes of infertility issues are varied, emerging evidence suggests that the gut microbiome plays a crucial role in reproductive health. The microbiome influences hormone regulation, immune system responses, and inflammation—three factors essential for fertility in both partners. For women, certain gut bacteria help metabolize and regulate estrogen, a hormone central to reproductive health. Disruptions in the microbiome can lead to hormonal imbalances, such as estrogen dominance, which is linked to conditions like PCOS and endometriosis, both common causes of infertility. For men, research suggests that gut dysbiosis—an imbalance of gut bacteria—may contribute to poor sperm quality and low testosterone levels, adding to fertility challenges. Regardless of sex, research suggests that a less diverse microbiome can hinder the body’s ability to regulate hormones and manage inflammation, creating a less hospitable environment for conception.
Declining Microbiome Diversity: Parallels with Rising Infertility
Over the last century, our gut microbiome has undergone unprecedented changes due to the overuse of antibiotics, exposure through diet to preservatives in processed foods, and increased exposure to environmental toxins. Research shows that people in industrialized nations have significantly lower gut bacteria diversity compared to indigenous populations, where fertility rates tend to be higher. This decline in microbial diversity mirrors the rise of chronic diseases and hormonal imbalances, key players in fertility struggles.
For those facing infertility, the emotional and physical challenges are immense. While stress, genetics, and lifestyle all play a role, the gut microbiome is now recognized as a significant factor. Supporting gut health offers a promising avenue for improving fertility, as the microbiome is intricately involved in areas critical to conception.
The Sperm Microbiome and Infertility: An Overlooked Factor
The role of the partner contributing sperm has often been overlooked in discussions of infertility. However, recent research shows that the microbiomes of both partners are critical to healthy fertility. The semen microbiome, in particular, can have a profound effect on sperm quality and overall reproductive outcomes. Studies have shown that bacterial imbalances in the genital tract (again, “dysbiosis”) can negatively affect sperm motility, concentration, and morphology. As one example, bacteria like Prevotella and Mycoplasma hominis have been associated with reduced sperm quality and increased DNA fragmentation, while beneficial bacteria such as Lactobacillus have been linked to improved sperm parameters. Given this influence, it has become clear that addressing microbiome health in both partners is critical to create the optimal environment for conception; a whole-body, microbiome-centered approach not only supports reproductive health but also provides a more inclusive and comprehensive strategy to fertility care.
The Estrobolome: Gut Microbes and Estrogen Regulation
One critical way the gut microbiome influences fertility is through the estrobolome—a collection of gut bacteria that regulate estrogen metabolism. The estrobolome produces enzymes like beta-glucuronidase, which help reabsorb estrogen into circulation. When the gut microbiome is disrupted, this delicate balance can be thrown off, leading to high levels of circulating estrogen, which can contribute to estrogen-dependent conditions like PCOS, endometriosis, and infertility.
By maintaining a healthy gut microbiome, individuals can help modulate estrogen levels, reduce inflammation, and support hormonal balance. This balance can not only enhance fertility outcomes but also improve overall reproductive health, and critical to maintaining this balance is consuming enough dietary fiber and ensuring regular bowel movements. Fiber aids in the elimination of excess estrogen through the bile, which is then expelled through stool. Regular bowel movements prevent estrogen from being reabsorbed into circulation, reducing the risk of hormone imbalances that contribute to fertility issues. Supplements like calcium D-glucarate can also support estrogen detoxification by inhibiting beta-glucuronidase, aiding the body in eliminating excess estrogen more efficiently.
The Vaginal Microbiome: A Critical Component of Reproductive Health
The vaginal microbiome, much like the gut, is a key player in fertility. Dominated by Lactobacillus species, the vaginal microbiome helps maintain a low pH, which protects against harmful pathogens and supports overall reproductive health. Disruptions in this balance—known as vaginal dysbiosis—can lead to conditions like bacterial vaginosis (BV), which has been linked to infertility and poor reproductive outcomes.
For individuals with chronic vaginal dysbiosis, a novel treatment called Vaginal Microbiome Transplant (VMT) is emerging. Similar to fecal transplants, VMT transfers healthy vaginal microbiota from a donor to a patient with recurrent BV or other chronic vaginal health issues. Early studies suggest that restoring balance in the vaginal microbiome through VMT may improve fertility outcomes by reducing infections and inflammation. If you are curious to learn more about VMT and its promise for reproductive health, I recommend AntheraVMT.
Supporting the Microbiome: Tools for Better Reproductive Health
Improving gut, semen, and vaginal microbiome health may just be the most powerful tools we have to address infertility issues. A diet rich in fruits and vegetables and prebiotic fibers nourishes beneficial bacteria, while fermented foods like yogurt and sauerkraut introduce live cultures to replenish the gut. Reducing sugar and processed food intake helps to curb the growth of harmful bacteria that thrive in dysbiotic conditions.
Probiotic supplements and postbiotics—non-living microbial byproducts—are also gaining attention for their ability to restore microbiome diversity. While products like ThaenaBiotic® offer microbial metabolites that can help support the gut microbiome, it is important to remember that no supplement alone can impact infertility. Rather, fostering a healthy microbiome is one vital part of working toward creating a fertile, supportive environment within the body.
Building Fertility-Friendly Health Habits
To support both fertility and overall health, consider adopting a lifestyle that encourages a balanced microbiome. Incorporating a wide variety of plant-based foods, prioritizing fiber, and introducing pre- and postbiotic-rich foods into your diet can make a big difference. Avoiding processed foods, managing stress, and maintaining a healthy metabolic state through regular exercise also contribute to hormone balance and fertility.
A Hopeful Path Forward
As chronic health issues rise alongside infertility statistics, it is becoming increasingly clear that our rapidly depleting microbiome diversity runs parallel to these troubling trends. Modern lifestyles, characterized by processed foods, high sugar intake, and overexposure to preservatives and antibiotics, have drastically reduced the diversity of our gut bacteria. The role of xenoestrogens and plastics on both our systemic hormone health and that of our microbiome is just starting to be revealed and cause alarm bells. This decline in microbial health could be contributing to fertility struggles in ways we are just beginning to understand, and although the body of research relating to infertility and the microbiome is more recently growing, it offers us some hope. By focusing on gut, sperm, and vaginal health, individuals can take proactive steps to support their fertility. There is and may never be one solution, nurturing the microbiome—through diet, supplements, and lifestyle changes—creates a fertile foundation for those striving to conceive. While science continues to uncover the intricate ways in which our microbiome impacts fertility, we can look forward to new, holistic strategies that empower and uplift those on the path to parenthood.
References
Farahani, L., Tharakan, T., Yap, T., Ramsay, J. W., Jayasena, C. N., & Minhas, S. (2021). The semen microbiome and its impact on sperm function and male fertility: A systematic review and meta-analysis. Andrology, 9(1), 115–144. https://doi.org/10.1111/andr.12886
Wang, H., Xu, A., Gong, L., Chen, Z., Zhang, B., & Li, X. (2022). The microbiome, an important factor that is easily overlooked in male infertility. Frontiers in Microbiology, 13, 831272. https://doi.org/10.3389/fmicb.2022.831272
Zhao, C., Wei, Z., Yang, J., Zhang, J., Yu, C., Yang, A., Zhang, M., Zhang, L., Wang, Y., Mu, X., Heng, X., Yang, H., Gai, Z., Wang, X., & Zhang, L. (2020). Characterization of the vaginal microbiome in women with infertility and its potential correlation with hormone stimulation during in vitro fertilization surgery. mSystems, 5(4). https://doi.org/10.1128/mSystems.00450-20
Salliss, M. E., Farland, L. V., Mahnert, N. D., & Herbst-Kralovetz, M. M. (2021). The role of gut and genital microbiota and the estrobolome in endometriosis, infertility and chronic pelvic pain. Human Reproduction Update, 28(1), 92–131. https://doi.org/10.1093/humupd/dmab035