Probiotics and Prebiotics: The Duo That Cares for Your Inner Universe
For decades, medical science treated the gut as a simple digestive tube. Today we know it's an intelligent organ,
The Vaginal microbiome it is one of the most studied microbial ecosystems and, at the same time, one of the most unknown among the general population. Unlike the gut microbiota, the vaginal microbiome has a unique characteristic in nature: in healthy conditions, it is dominated by a single bacterium, instead of the diversity we find in other microbial ecosystems of the body.
Understanding how it works, what alters it and how to care for it is essential for women's gynaecological, reproductive and even general health. In this guide you will find everything you need to know with scientific evidence updated to 2026.
Article Contents
The vaginal microbiome is the collection of microorganisms - primarily bacteria - that permanently live in the vagina and cervix. Its composition is radically different from that of other microbial ecosystems in the body: while the gut microbiota needs diversity to be healthy, the vaginal microbiome functions best when dominated by bacteria of the genus Lactobacillus.
This ecosystem is influenced by oestrogen: during puberty, the vaginal epithelium accumulates glycogen, which serves as a food source for Lactobacillus. These, in turn, produce acid lactic and maintain an acidic pH that protects against infections. During the menopause, as oestrogen levels drop, this balance is significantly altered.
95%of the vaginal microbiome | 3,8–4,5Vaginal pH | 5main types of | 30%Vaginal infections in women |
Vaginal microbiota or microbiome? Both terms are used interchangeably, although with precision: the vaginal microbiota refers to the microorganisms themselves, while the microbiome also includes their genes, metabolites, and interaction with the vaginal environment.
Researchers have classified the vaginal microbiome into five main groups, or Community State Types (CSTs), based on which bacterial species predominates or if there is an absence of clear dominance:
CST I — Lactobacillus crispatus
The most protective. It is associated with a lower risk of infections, better reproductive health, and healthier pregnancies. It is the most studied profile and considered the most beneficial.
CST II — Lactobacillus gasseri
Less frequent. Produces lactic acid but in smaller quantities than CST I. It is also associated with good vaginal health.
CST III — Lactobacillus iners
The most common but also the most fragile Lactobacillus. It produces less lactic acid and is associated with greater vulnerability to ecosystem disturbances.
CST IV — No clear dominance (Gardnerella, Prevotella, Mobiluncus…)
The highest risk. High bacterial diversity but absence of Lactobacillus dominance. It is associated with bacterial vaginosis and increased susceptibility to sexually transmitted infections.
CST V — *Lactobacillus jensenii*
Infrequent. Produces D-lactic acid. Generally protective profile, though less studied than CST I.
Key fact: Women of African and African American origin more frequently present with CST IV (without Lactobacillus dominance), which shows that genetic and ethnic diversity influences the vaginal microbial composition. This has important implications for research and clinical recommendations, which have historically been based on Caucasian populations.
Lactobacillus is central to vaginal health. These bacteria produce several protective substances that act as a natural defence system:
Lactic acid
It maintains vaginal pH between 3.8 and 4.5, creating a hostile environment for pathogens such as Gardnerella vaginalis, Candida albicans and Chlamydia trachomatis.
Hydrogen peroxide (H₂O₂)
Produced mainly by L. crispatus, it has a direct antimicrobial effect and protects against pathogens.
Bacteriocins
Peptides with antibiotic activity produced by Lactobacillus themselves, which inhibit the growth of competing and pathogenic bacteria.
D-lactate
Isomer of lactic acid with greater antimicrobial potency. Produced especially by L. crispatus and L. jensenii. Strengthens the mucosal barrier.
Regulation of the local immune system
Lactobacillus interacts with vaginal epithelial cells by modulating the inflammatory response, which reduces the risk of infections and promotes immune tolerance during pregnancy.
Vaginal pH is one of the most useful and straightforward markers for assessing the health of the vaginal microbiome. An acidic pH (between 3.8 and 4.5) indicates a predominance of Lactobacillus and good vaginal health. A high pH (above 4.5) is a warning sign of possible imbalance.
Vaginal pH | Usual situation | Interpretation |
3,8 – 4,5 | Reproductive age, healthy microbiome | ✅ Optimal |
4.5 | Bacterial vaginosis, menopause, period | ⚠️ Alert |
6.0 – 7.0 | Active infection, severe vaginal atrophy | 🔴 Intervention |
Vaginal pH can be measured with test strips available at pharmacies. It is an accessible self-monitoring tool, although it does not replace clinical evaluation in case of symptoms.
Vaginal dysbiosis occurs when the balance between Lactobacillus and other bacteria is disrupted, favouring the growth of potentially pathogenic microorganisms. It is more common than people think and often occurs without obvious symptoms.
Main factors that alter the vaginal microbiome
Systemic antibiotics They eliminate pathogenic bacteria but also vaginal lactobacilli. The impact can last for weeks or months.
Vaginal douches: They alter the pH and eliminate protective flora. They are advised against by all gynaecological societies.
Unprotected sex Semen has an alkaline pH (7.2-8.0), which temporarily alters vaginal pH. A partner's microbiome can also have an influence.
Hormonal changes Menopause, postpartum, hormonal contraceptives: they modify oestrogen levels and, consequently, the availability of glycogen for Lactobacillus.
Chronic stress and lack of sleep They elevate cortisol, which suppresses local immunity and alters the vaginal microbial balance.
Smoking It is associated with a higher prevalence of bacterial vaginosis. Nicotine alters the vaginal hormonal and immune environment.
Diet high in sugar It favours the growth of Candida albicans and can alter the Lactobacillus/other bacteria balance.
Use of intimate products with an inappropriate pH Soaps, gels, or wipes with a neutral or alkaline pH alter the protective vaginal ecosystem.
Just like the gut microbiome, the vaginal one is also malleable. These are the strategies with the most evidence for keeping it balanced:
01 Use intimate hygiene products with an acidic pH
Choose intimate soaps or gels with a pH between 3.5 and 4.5. Avoid conventional bath soaps (pH 7-9) in the vulvar area. The vagina is self-cleaning: you do not need to clean the inside.
02 Avoid vaginal douches
Douching is contraindicated by all gynaecological guidelines. It alters the pH, eliminates protective flora, and increases the risk of bacterial vaginosis and STIs.
03 Use a condom
Semen temporarily alters vaginal pH. Consistent condom use protects the microbial ecosystem, especially in relationships with new partners.
04 Watch your diet
Reduce the refined sugar (favours Candida). Include fermented foods (yogurt, kefir) that provide *Lactobacillus*. A healthy gut microbiota also benefits the vaginal microbiota.
05 Take probiotics after antibiotics
If you need to take systemic antibiotics, consider supplementing with vaginal probiotics or consuming plain yogurt to speed up the recovery of your vaginal microbiome.
06 Choose cotton underwear
Cotton allows for breathability and prevents excessive moisture that promotes fungal growth. Avoid tight, synthetic underwear.
07 Manage stress and sleep
Chronic stress elevates cortisol, which suppresses local vaginal immunity. Restorative sleep and stress management techniques have a direct impact on microbiome health.
The vaginal probiotic market has grown exponentially in recent years. The scientific evidence is promising but requires significant nuances.
Oral probiotics with vaginal strains
Strains such as Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 are capable of colonising the vagina after oral administration, migrating from the gut. These are the strains with the most clinical evidence for vaginal health.
Direct vaginal probiotics (suppositories/capsules):
Direct administration of Lactobacillus into the vagina. They have a faster effect but less durability. Useful as complementary treatment after bacterial vaginosis or candidiasis.
Vaginal prebiotics
Substrates such as glycogen or oligosaccharides that feed endogenous Lactobacillus. An emerging therapeutic avenue with promising preliminary results.
Vaginal Microbiome Transplantation (VMT)
Experimental technique consisting of transferring vaginal microbiomes from healthy donors. Clinical trials are already underway in women with recurrent dysbiosis and promising results in women with Sjögren's syndrome and HIV.
Important The effectiveness of vaginal probiotics depends on the specific strain, dosage, and clinical indication. Not all products on the market have the necessary evidence. Always consult with your gynaecologist or family doctor before starting a supplement.
Does the vaginal microbiome change throughout the menstrual cycle?
Yes. During menstruation, vaginal pH rises (blood has a pH of 7.4), which temporarily reduces lactobacilli and encourages the growth of other bacteria. During the follicular phase, the microbiome recovers with increased oestrogen. These changes are normal and to be expected.
Does vaginal discharge indicate anything about the microbiome?
Normal vaginal discharge is clear or whitish, without a strong odour, and varies in amount and consistency throughout the cycle. Discharge with a fishy smell, a greyish or yellowish colour, accompanied by itching or burning, may indicate dysbiosis or infection and requires medical evaluation.
Does the menopause affect the vaginal microbiome?
Yes, significantly. The drop in oestrogen reduces available glycogen, which lowers Lactobacillus and raises vaginal pH. This increases the risk of atrophy, dryness, infections, and sexual discomfort. Treatment with local oestrogen can partially restore the vaginal ecosystem.
Do hormonal contraceptives affect the vaginal microbiome?
Studies show mixed results. Some hormonal contraceptives appear to stabilise the microbiome by regulating oestrogen; others can alter it. Pills with high doses of progestin may reduce Lactobacillus. Current evidence is insufficient to make general recommendations.
Do sexual relations between women affect the vaginal microbiome?
Yes. Female couples share vaginal microbiomes more directly than in heterosexual relationships. Similarities in microbial profiles have been observed in cohabiting female couples, suggesting a bidirectionality in microbiome influence between same-sex partners.
Can a vaginal microbiome analysis be performed?
Yes, there are commercial vaginal microbiome sequencing tests available. However, their clinical utility remains limited outside of research and assisted reproduction protocols. pH and symptoms continue to be the main assessment tools in routine clinical practice.
For decades, medical science treated the gut as a simple digestive tube. Today we know it's an intelligent organ,
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