“Although for a long time they were studied as independent compartments, we now know that the intestinal and vaginal microbiota are connected through what is called the gut-vagina axis,” Silvia P. González, PhD, president-elect of the Spanish Association for the Study of Menopause and a specialist in menopause and human microbiota with a master’s degree in climacteric and menopause, told El Médico Interactivo, part of the Medscape’s Professional network.

Intestinal bacteria, mainly of the genus Lactobacillus, can migrate from the gut to the urogenital tract because of anatomical proximity. In addition, systemic inflammation caused by intestinal imbalances (dysbiosis) can affect the vaginal microbiota, promoting imbalances.

Balanced Vaginal Ecosystem

From a gynecologic point of view, this has implications: Women with intestinal disturbances may be more susceptible to vaginal infections, bacterial vaginosis, candidiasis, sexually transmitted infections, and an increased risk for pregnancy complications.

“A balanced vaginal microbiota is characterized by the predominance of the genus Lactobacillus, which allows the formation of a biofilm that coats the mucosa and thus protects it from external aggressions. The most common species during the reproductive period are Lactobacillus iners, Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii,” Gema Fernández-Rivas, MD, spokeswoman for the Spanish Society of Infectious Diseases and Clinical Microbiology, told El Médico Interactivo.

Factors that disrupt this balance and can cause dysbiosis are diverse. They include biological factors such as hormonal changes during puberty, pregnancy, or menopause; medical factors such as use of broad-spectrum antibiotics, vaginal antiseptics, or douching; and lifestyle factors such as chronic stress, a poor diet, and smoking, which negatively affect the vaginal ecosystem. Less obvious factors also matter, such as the type of underwear and the use of intimate hygiene products with harsh fragrances.

Most Frequent Imbalances

“Among the most frequent imbalances is bacterial vaginosis, which affects between 20% and 30% of women of reproductive age. This condition is characterized by a decrease in lactobacilli and an overgrowth of anaerobic bacteria such as Gardnerella vaginalis, Prevotella, or Mobiluncus,” González said. Another common disorder is vulvovaginitis caused by Candida, especially after antibiotic cycles or in cases of immunosuppression.

In the perimenopausal stage and during menopause, the microbiota pattern changes: The drop in estrogen causes atrophy of the vaginal epithelium and an impoverished microbial ecosystem, leading to the genitourinary syndrome of menopause (GSM), which manifests as dryness, irritation, dyspareunia, and recurrent urinary tract infections. This phase, González said, is often underdiagnosed and undertreated, and the vaginal microbiota plays a central role that requires a proactive approach.

Strain-Specific Efficacy

Fernández-Rivas explained that probiotics can help restore the vaginal microbiota after bacterial vaginosis, reduce recurrence, and act as adjuncts following antibiotic treatment, although she warns that available studies are still limited, with small sample sizes and great heterogeneity in strains, doses, and routes of administration, “which makes it necessary to develop larger clinical trials and clear therapeutic protocols.”

Along the same lines, González said the future is promising, “although there are still methodological limitations that must be acknowledged.” She emphasized that the evidence is solid for certain strains in conditions such as candidiasis and vaginosis. She also noted that research is emerging — and very interesting — in areas such as GSM, prevention of recurrent urinary tract infections, and even human papillomavirus (HPV) infection. “Probiotics have ceased to be an anecdotal complementary strategy and have become a therapeutic tool with a real scientific basis,” she said.

From the perspective of community pharmacy practice, the assessment is favorable, but with some nuances. “The biological concept is coherent, but not all probiotics are the same, and not all strains have the same evidence, so not all products should be recommended with the same level of confidence,” Piluca Barrau, pharmacist specializing in women’s health and dermocosmetics, told El Médico Interactivo. “From the counter, they are proposed as a complementary strategy for women prone to dysbiosis or recurrences, not as a substitute for diagnosis or treatment,” she added.

Strain Viability Matters

The effectiveness of probiotics given orally depends on the bacteria surviving passage through the stomach and intestine and being able to colonize or influence the vaginal microbiota. “Not all probiotic strategies offer the same efficacy, and one of the determining factors, often poorly explained, is the real capacity of the strains to survive gastrointestinal transit and exert a relevant biological effect,” said Susana Maria Costa Pereira, specialist in gynecology and obstetrics.

González added that encapsulation technology is equally important. “Formulations with enteric coatings or microencapsulation offer superior protection and improve viability,” she specified. Direct vaginal administration would bypass this problem, though it may have limitations in adherence and patient comfort. Ideally, clinicians should know not only the genus and species of the probiotic they prescribe but also the specific strain and the evidence of survival for that formulation.

Some Lactobacillus strains have demonstrated gastroresistance. There is level 1 evidence for the efficacy of patented lactobacilli such as Lactobacillus rhamnosus GR-1, Lactobacillus reuteri B-54, and L reuteri RC-14 in restoring normal vaginal flora, reducing the number of infections by more than 50% in women with daily oral treatment and up to 79% in women with weekly vaginal treatment.

Comprehensive and Nutritional Approach

Beyond pharmacologic treatment, maintaining vaginal balance depends largely on diet and lifestyle. From this perspective, Cala H. Cervera, orthomolecular nutritionist, told El Médico Interactivo that intestinal and vaginal health cannot be understood in isolation but rather as part of an interconnected system. Her therapeutic approach promotes the idea of “recovering the biological nature of the person.” This implies learning to listen to the body, respecting its rhythms and reeducating habits that deviate from natural physiology. “It’s not about teaching the body to be healthy but about eliminating the factors that harm it and allowing it to recover its balance by itself,” she explained.

Cervera said that when diet is not aligned with biological needs, the digestive system struggles to process and absorb nutrients properly, generating residues that can ferment or decompose, causing inflammation of the intestinal mucosa and altering the microbiota. This dysbiosis, in addition to favoring local infections, can affect other areas of the body, including the vaginal microbiota, because of its impact on immunity and nutrient absorption.

Lifestyle habits should also align with biology. Adequate rest, moderate exercise, stress management, affectionate relationships, and a sense of safety are fundamental to maintaining homeostasis and supporting overall health, Cervera said.

Research Directions and the Future

“The study of the vaginal microbiota represents an interesting and very promising field in microbiology and gynecology. Better understanding of this ecosystem will make it possible to develop more effective preventive and therapeutic strategies based not only on eliminating pathogens but also on restoring and maintaining the natural microbial balance,” Fernández-Rivas said. Among the main lines of research, she highlighted the development of Lactobacillus strains with a greater and more durable capacity to colonize the vaginal mucosa, study of vaginal microbiota transplantation and progress toward personalized medicine based on individual microbiological profiles, and the role of the vaginal microbiota in various pathologies and its interaction with the immune system, with both therapeutic and diagnostic potential.

A review warns that current knowledge is biased because much of the research has been conducted in Western populations. This may lead to an incomplete definition of what is considered a “normal” vaginal microbiota and reinforces the need to expand research to more diverse populations to advance truly personalized approaches. Initiatives such as the Isala project, a multinational research effort to broaden knowledge about vaginal microbiome diversity by involving thousands of women in different countries, are helping to generate wider datasets and open new research avenues.

To these areas, González added research into the role of the vaginal microbiota in cervical cancer risk, the effectiveness of HPV vaccination, and the progression of precancerous lesions — research that is producing revealing data that could transform follow-up protocols. She also cited a study of postbiotics, which offer new therapeutic opportunities with greater stability and safety. Finally, the microbiota-immunity-fertility axis is emerging as a promising field, with direct implications for assisted reproduction and prevention of preterm birth.

González closed with a message to health professionals to take responsibility and continue training in this field. “The vaginal microbiota has ceased to be a niche topic and has become a cross-cutting axis of women’s health throughout life. From adolescence to menopause and beyond, the vaginal ecosystem both reflects and conditions a woman’s overall health. Health professionals have a responsibility to train in this field and not trivialize GSM symptoms.”

This story was translated from El Médico Interactivo on Univadis, part of the Medscape Professional Network.