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The potential benefits and risks of probiotics are often discussed in the context of gut health. Yet the human microbiome extends far beyond the gut ecosystem, with beneficial microbes inhabiting not only our digestive tract but also our skin, reproductive system, and virtually every nook and cranny of our body. So might probiotics have benefits outside of the gut? Indeed, evidence suggests they may have another promising application: supporting the health of the female reproductive system.
The Urogenital Microbiome
Changes in the urogenital microbiome in females are increasingly being recognized for their significant influence on the risk of infections. A “healthy” vaginal microbiome differs somewhat across women of different ethnicities and geographic locations but, before puberty, is generally dominated by lactobacilli, which play a crucial role in maintaining a healthy urogenital environment. These bacteria produce lactic acid and hydrogen peroxide, which maintain an acidic pH and help suppress the growth of potentially harmful microorganisms. However, upon puberty, factors like hormonal changes and sexual activity can dramatically transform the vaginal microbiome’s composition, potentially causing lactobacilli to lose their dominance. This decrease in lactobacilli can cause the environment to become less acidic, thus encouraging the growth of pathogenic bacteria and other harmful microorganisms and increasing the risk of various urogenital infections.
Aging can similarly affect the vaginal environment. During puberty, the influence of estrogens on the glycogen content of vaginal epithelial cells likely aids in lactobacilli becoming the primary inhabitants of the vagina. This rise in estrogen levels encourages maturation, proliferation, and glycogen accumulation within the epithelial cells. On the other hand, menopause, marked by a substantial decline in estrogen production, instigates the drying and atrophy of the vaginal epithelium. This reduction in estrogen is paired with a decrease in the glycogen content of the vaginal epithelium, subsequently leading to a reduction in lactobacilli population.
Shifts in the balance of vaginal microorganisms can heighten the risk of urogenital infections caused by foreign microbes, but such shifts can also result in pathologies directly. Bacterial vaginosis (BV), for instance, is a prevalent infection of the urogenital tract and is defined by a disruption in the natural balance of the vaginal microbiome. Though a healthy vagina is a habitat to a diverse array of bacteria, when specific types multiply excessively, it unsettles the harmony and results in BV, which manifests through symptoms like itching, irritation, and an unpleasant odor. In other words, this condition develops as a result of overgrowth among certain normal vaginal microbes – particularly Gardnerella vaginalis, Mycoplasma hominis, Prevotella spp., Peptostreptococcus spp., Mobiluncus spp., Bacteroides spp., Atopium vaginae, and Megasphera spp. – and without the introduction of foreign, pathogenic species.
Can Probiotics Help?
To counter shifts in microbial composition, research has increasingly highlighted the importance of probiotics in promoting a healthy vaginal environment, particularly through their ability to boost the presence of lactobacilli. Several studies have investigated the effects of lactobacilli-containing supplements, administered either orally or as vaginal suppositories, on the vaginal microbiome in adult women. The majority of these trials have observed a significant increase in the levels of vaginal lactobacilli following supplementation.
But can this augmentation of lactobacilli populations offer protection against recurrent vaginal infections, such as bacterial vaginosis? Evidence to date suggests that the answer is yes.
A Case in Point: Bacterial Vaginosis
For instance, one noteworthy study conducted by Recine et al. highlighted the potential benefits of lactobacilli supplementation in managing BV among sexually active women. In this prospective case-control study, 250 non-pregnant women diagnosed with BV were split into two groups: Group A received standard BV treatment (500 mg oral metronidazole twice daily for 7 days), whereas Group B followed the same regimen but was additionally supplemented with Lactobacillus rhamnosus BMX 54 vaginal tablets, a commercial product sold as Normogin®. The investigators assessed patients at 2, 6, and 9-month timepoints, evaluating BV recurrence, vaginal symptoms, restoration of healthy vaginal flora, vaginal pH, and overall treatment tolerability.
By the 2-month mark, Group B showed significant improvement in restoring healthy vaginal flora, with 90.4% (113 patients) achieving this outcome compared to 79.2% (99 patients) in Group A (P=0.014). This disparity between the groups persisted at the 6-month evaluation, with 74.6% (106 patients) of Group B maintaining normal vaginal flora compared to only 25.4% (36 patients) in Group A (P<0.0001). The same was true for the 9-month mark.
At baseline, 88% of all participants had a vaginal pH above the physiological value of 4.5 – in other words, the environment was less acidic than in a healthy condition. By the 2-month follow-up, there was no significant difference in pH between the groups (P=0.524), with Group A averaging a pH of 4.27±0.54 and Group B at 4.23±0.44 – both within a healthy physiological range. However, by the 6-month mark, the average vaginal pH for Group A had begun to creep back upwards (4.48±0.57), a statistically significant difference from Group B (4.34±0.38, P=0.034). This trend continued at the final 9-month assessment, with Group B maintaining a significantly lower median pH (4.23±0.33) compared to Group A, which by that point had, on average, exceeded the healthy range (5.05±0.54, P<0.001).
As expected, improvement in BV symptoms was directly related to a return to a physiological vaginal pH. After 9 months, 92% of patients treated with probiotics saw symptom improvement, in contrast to 79% of patients treated without probiotics (P<0.001). Overall, this study indicates that integrating Lactobacillus rhamnosus BMX 54 vaginal tablets into standard antibiotic treatment can help restore a healthy vaginal environment and reduce BV recurrence.
Broader Perspectives on Probiotics & Female Health
Similar findings have been reported in other interventional studies in women with BV as well as other vaginal infections, such as yeast infections and aerobic vaginitis. As with BV, research on these other conditions has generally shown that supplementation with lactobacilli-containing probiotics can both increase recovery from active infections (when combined with conventional treatments) and reduce the risk of recurrence. Collectively, these findings emphasize the potential value of probiotic supplementation in promoting vaginal health.
Still, intricacies in the dynamics of the vaginal microbiome deserve further exploration. Though mounting evidence points towards the potential of probiotics to promote a more balanced vaginal microbiome and reduce infection risk, the effectiveness of these interventions can vary substantially across individuals for reasons that aren’t entirely clear. Moreover, though researchers widely agree that lactobacilli are key players in maintaining a healthy vaginal environment, a lack of clarity persists regarding specific species within this genus that may offer the greatest benefits, nor have we reached any consensus on optimal protocols and formulations. These open questions highlight the need for continued research, given the potential implications for preventive measures and treatment strategies against common urogenital infections.
While the ultimate goal remains to fully decode the complex relationship between probiotics, the vaginal microbiome, and host health, current evidence offers great promise that probiotic supplementation can improve women’s health and well-being.
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