The crosstalk between female hormones and the vaginal microbiome

The Crosstalk Between Female Hormones and the Gut & Vaginal Microbiomes

The gut and genital tract microflora of females are complex biological ecosystems that are in continuous communication with each other. The bacteria that colonise the vagina evolved through translocation of bacteria from the gut to the vagina, or through mother-to-child transfer during delivery. The vaginal microbiome is composed of over 200 species and is unique to each female, as it differs depending on genes, age, hygiene, dietary habits, ethnicity, and use of lubricants or medications.^1,2 The overall health of the vagina depends on several factors, namely a healthy balance of the hormones oestrogen and progesterone, good quality connective tissue, and a robust and diverse balance of beneficial bacteria that reside in the genital area which make up the vaginal microbiome.³ The normal vaginal microflora consists of Lactobacillus bacteria that emerge from the gut. This includes L. crispatus, L. gasseri, L.rhamnosus, L. salivarius, and L. plantarum with some Bifidobacterium species. These strains produce lactic acid, which maintains the vaginal pH to be within the required 3.5-4.5. This acidity is essential to prevent opportunistic bacteria from proliferating uncontrollably. Lactobacillus strains also exert a natural antimicrobial and anti-inflammatory effect, which keeps foreign bacteria at bay. Other commensal anaerobic species with great propensity to becoming pathogens, especially when Lactobacilli are depleted include Gardnerella, Prevotella, Megasphaera, Atopobium, Streptococcus, Mobiluncus, Mycoplasma and Peptoniphilus. When in high levels, these strains may contribute to vaginal infections such as bacterial vaginosis (BV).⁴

Pathogenic infections within the gut e.g. Escherichia coli (E. coli) and Candida strains (mostly Candida albicans) are thought to directly affect bacterial composition of the vagina due to their ability to translocate to the vagina and multiply.⁵

The Role of Oestrogen in Regulating the Vaginal Microbiome

Oestrogen is particularly important to promote healthy epithelial and connective tissues of the vagina, therefore fluctuations in oestrogen levels have their part to play in the lubrication and bacterial balance of the vagina. The vaginal microbiome evolves over a women’s lifetime due to these natural increases and decreases in oestrogen. During childhood, the vagina has a more alkaline pH and is predominantly colonised by cutaneous and faecal microorganisms, but hormonal changes in puberty cause the pH to decrease, becoming more acidic, which allows Lactobacillus species to proliferate.6 The vaginal microbiome also changes during pregnancy, showing reductions in richness and diversity, becoming predominantly Lactobacillus strains due to oestrogen affecting the thickness of vaginal mucosa. This change may be a contributing factor to an increased risk of vulvovaginal candidiasis during pregnancy.⁷ During the menopause, there are significant changes to the vaginal microbiome again,² as oestrogen levels decrease, we also see a reduction in Lactobacilli, leading to colonisation with cutaneous microorganisms, including Staphylococcus, which leads to an increase in pH.^8,9 The combination of low oestrogen and a reduction in Lactobacilli strains can contribute to symptoms such as vulvovaginal atrophy, vaginal dryness and infections such as vulvovaginal candidiasis and bacterial vaginosis.^10,11

Possible Causes of Vaginal Dysbiosis

Vaginal infections are very common in women from their teenage years through to menopause. It’s estimated that around 75% of women experience vulvovaginal candidiasis within their lifetime,¹² and 29.2% will have an occurrence of bacterial vaginosis.¹³ Unfortunately, women who have hormonal imbalances are prime targets for reoccurring vaginal infections. The menstrual cycle alone can contribute to changes within the vaginal microbiome. For example, the pH of the vagina can increase during menses due to menstrual blood being slightly alkaline, which contributes to changes in the vaginal microbiome and increased susceptibility to infections during that time.¹⁴

There are mixed results when investigating the effects of hormonal contraceptives on the vaginal microbiome. Some studies have found that hormonal contraceptive use can alter the microbiome in a negative way, increasing the risk of sexually transmitted diseases, bacterial vaginosis, and overgrowths of Candida albicans.15,16 Progestin-only contraceptives have been found to reduce overall abundance of Lactobacillus species.¹⁷ However, other studies have found that combined oral contraceptives increased the abundance of Lactobacillus species, while reducing growth of pathogenic species.¹⁸

The oral contraceptive pill can cause decreases in the diversity and abundance of the gut microbiome,¹⁹ as well as depletion of nutrients needed for hormones, structure, and immune function. This includes B vitamins, vitamin C, E, zinc, selenium, and magnesium.²⁰ The depletion of the essential nutrients, especially folate, vitamin B6, zinc and vitamin E,²¹ alongside changes within the gut, may play a role in the development of more severe and recurrent vaginal infections.²² This may indicate a need for women on birth control to take a probiotic supplement alongside additional nutrients.

Other common causes of vaginal microbiome disruption include:

Diet (High glycaemic load & low nutritional density)

Smoking

Exposure to synthetic chemicals, toiletries, and fragrances that upset vaginal pH and bacteria

Changes in the vaginal pH as a result of exposure to semen

Vaginal douching

Medications: Oral Contraceptive Pill (OCP), Hormone Replacement Therapy (HRT), steroids,²³ and antibiotics.

Restoring the Vaginal Microbiome

Both oral and topical probiotics can support the vaginal microbiome by secreting antimicrobial peptides such as lactic acid, hydrogen peroxide, and bacteriocin, which maintain the vaginal acidic pH, making it more difficult for pathogens to establish themselves.²⁴ Additionally, probiotic supplementation may have indirect effects on the vaginal microbiome through alteration of the estrobolome. This collection of bacteria can influence circulating oestrogen levels through the secretion of enzymes such as beta-glucuronidase which deconjugates oestrogens into their active forms.25 As vaginal dysbiosis is associated with increased risk of certain symptoms and conditions, you may consider a probiotic in women who suffer with recurrent thrush, BV, or urinary tract infections (UTIs), currently on birth control, planning pregnancy, or going through the menopause.

There are a few key strains that can be particularly beneficial for maintaining female health:

Lactobacillus rhamnosus – Has anti-microbial properties against S.aureus and E.coli, ^{26 27} helping to restore vaginal pH and control bacterial vaginosis symptoms.28 In one study, after 28 days of daily oral supplementation of Lactobacillus rhamnosus resulted in an increase in vaginal Lactobacilli and a significant decrease in yeast and coliforms. ²⁹

Lactobacillus crispatus – Is representative of a healthy vaginal microflora, due to being the dominant species of the vaginal microbiota. ³⁰ It offers protection against Candida albicans, especially against Candida translocation, ³¹ as well as a Chlamydia, Bacterial Vaginosis and UTIs. ³² It is also associated with lower risk of pre-term birth. ³³

Lactobacillus salivarius – Produces antimicrobial peptides that can reduce growth of urogenital pathogens, including Candida albicans, but also Enterococcus faecalis and Neisseria gonorrhoeae. ^34,35

Lactobacillus gasseri – Is a strong producer of lactic acid which helps to inhibit the growth of E.coli and Candida albicans adhesion. ³⁶ Supplementation of Lactobacillus gasseri daily in women aged 20-38 for 6 months significantly reduced PMS symptoms, including improved emotional wellbeing. ³⁷ Supplementation has also shown to result in a significant decrease in endometriotic lesions via activation of NK cells. ³⁸

With vaginal infections being so common in women, it is encouraging to see the potential probiotic supplementation has in supporting women and reducing the risk of both symptoms and infections. It’s important to note the bi-directional relationship between the microbiome and oestrogen, which may emphasise the need to consider both areas while supporting female health. In addition, the natural shifts in oestrogen over a woman’s lifetime can influence both the structure and microbiome of the vagina, which have an overall effect on female health.

References

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