Vaginal Microbiome and the Influence of Probiotics

The Vaginal Microbiome

Millions of bacteria live within the human vagina. Although bacteria are commonly associated with infections and disastrous sequelae, the vast majority of them exist in mutualistic relationships that benefits the human host. The indigenous vaginal microbiota is necessary to maintain vaginal health. It prevents colonization and subsequent infection by competitively excluding foreign invasive organisms that may cause disease. 

Lactobacillus species, such as L. crispatus, L. iners, L. gasseri, and L. jensenii, are the predominant vaginal microbiota found in the majority of women.¹ The predominance of Lactobacilli in the vagina is unique to humans compared to other species. It is believed that this is due to our high intake of starch, leading to increased levels of glycogen in the vaginal tract. The high levels of glycogen promote the proliferation of Lactobacilli.² Lactobacilli create an acidic environment in the vagina by producing lactic acid. This acidic environment can inhibit the growth of certain bacterial species that may cause harm. Lactobacilli also produces additional antimicrobial products, including bacterioicin and biosurfactants, that act as a defense mechanism to actively suppress the growth of foreign invading microogranisms.³

Consequences of a Disrupted Vaginal Microbiota: Bacterial Vaginosis

Bacteria vaginosis (BV) is the most common vaginal condition that affects women in their reproductive age.¹ It is characterized as the disruption of the equilibrium of the normal vaginal microbiome, resulting in an increased risk of invasion by infectious agents. There has been a shift in the vaginal microbiome from the normally predominant Lactobacilli to one dominated by G. vaginalis, Mobiluncus, Prevotella, and Bacteriodes, individually or in combination. These species are all known to promote a pro-inflammatory immune response.¹ 

The vaginal epithelium is an important mechanical barrier that protects from invading microorganisms that may cause disease. Bacteria associated with bacterial vaginosis disrupts the integrity of the vaginal epithelial immune barrier. As a result of the disrupted microbiome and vaginal epithelial barrier, BV is an important risk factor for: 

• Acquiring sexually transmitted infections (STIs) such as chlamydia, gonorrhea, and HIV
• Causing pelvic inflammatory disease (PID) which may lead to infertility
• Causing premature birth and many other reproductive and obstetric complications in pregnant women⁴  

Common symptoms of BV include

• Thin, whitish to grey vaginal discharge
• Pain, itching, or burning sensation in the vaginal area
• Strong fish-like odor, especially after sex
• Burning with urination⁴ 

Common risk factors for BV include

• Menstrual blood: due to a higher probability of a more diverse bacteria species colonizing the vagina⁵
• A new sexual partner
• Vaginal douching
• Smoking
• Lack of condom use¹
• Low estrogen levels associated with menstruation, postpartum, and menopause^5-7
• Recent antibiotic use⁸
• Stress⁸
• Weak immune system⁹

What is the Treatment for Bacterial Vaginosis?

In most women, symptoms of BV resolve on their own without intervention. When necessary, standard treatment of BV is antibiotics, either oral or topical. Unfortunately, reoccurrence of BV after treatment is common, with some studies citing an incidence as high as 30-40%.³ Antibiotic-resistant pathogens and the persistence of a susceptible vaginal environment both contribute to the recurrence of BV. Studies have shown that probiotics may reduce the reoccurrence of BV by recolonizing the vaginal microbiome with Lactobacilli. By recolonizing the vaginal microbiome with probiotics, this can reduce the lag time to reestablish a healthy microbiome. Therefore the most effective regimen for the treatment of BV is a combined regimen that includes a standard antibiotic with a long term probiotic supplementation of Lactobacilli.³ 

Dietary Connection to the Vaginal Microbiome

As mentioned before, the human vaginal microbiome is unique in bacterial composition in comparison to other mammals.² This unique microbiome may be due to dietary reasons, which along with the effectiveness of treating BV with oral probiotics may show a connection between the gut and vaginal microbiome.⁵ In general, supporting a healthy gut microbiome with Lactobacilli probiotics has been shown to be beneficial in treating BV.³ Fermented foods are also considered probiotics, and those rich in the Lactobacilli species may support a healthy vaginal microbiome. Prebiotics (starchy carbohydrates that don’t break down well in the gut) are also important to consider because they support the growth of healthy bacteria already present in the gut.⁵ 

Dietary Sources of Prebiotics

• Flaxseeds⁶
• Bananas¹⁰
• Apples¹⁰
• Oats¹⁰
• Onions and garlic¹⁰
• Asparagus¹⁰ 

Dietary Sources of Lactobacilli Probiotics¹¹

• Fermented vegetables: kimchee, sauerkraut, etc.
• Kefir
• Yogurt

Possible Dietary Connections of Bacterial Vaginosis

Although research on the specific dietary triggers is limited, this study has found the following to be risk factors for BV: 

• High intake of saturated fat⁹
  • Due to a tendency to increase the pH of the vagina⁹
• Low intake of micronutrients
  • Folate
  • Vitamin E (supports the immune system and acts as an antioxidant)

Key Takeaways

1. The human vagina is a host of microorganisms, predominantly Lactobacilli, that protect against foreign invasive bacterial species that can cause disease
2. Bacterial vaginosis is a prevalent vaginal condition caused by a disrupted vaginal microbiome
3. If necessary, effective treatment for bacterial vaginosis involves a combined regimen with both antibiotics and probiotics