May 2019 Issue

Probiotics for Vaginal Health
By Liz Weiss, MS, RDN
Today’s Dietitian
Vol. 21, No. 5, P. 30

An Exclusive Interview With Anthony Thomas, PhD, on the Merits of Supplementation to Prevent Common Urogenital Infections in Women

When dietitians think of probiotic supplements, gut health usually comes to mind, since probiotics have been found to help improve digestive health. But evidence shows that certain probiotic strains have the potential to support women’s urogenital tract health, too. Maintenance of a healthy vaginal microbiota may reduce the incidence of urogenital infections, the spread of sexually transmitted diseases, and adverse pregnancy outcomes, thus decreasing the need for conventional antimicrobial treatments.1

While there’s no vaginal microbiota classified as normal, it’s known that vaginal environments containing high levels of specific bacteria from the genus Lactobacillus generally are healthy.2 And it’s common knowledge that when the vaginal microbiota has fewer Lactobacillus strains and increased diversity of nonbeneficial bacteria, it’s more susceptible to dysbiosis.3-7

The ramifications of vaginal dysbiosis are many. Bacterial vaginosis (BV) and urinary tract infections (UTIs) are some of the most common issues, and both are becoming more resistant to the antimicrobials conventionally prescribed to treat them.8 Moreover, these same antimicrobials can further contribute to vaginal dysbiosis. Many issues either can recur or, if healed, lead to other problems, such as yeast infections. Pregnant women with vaginal microbiota dysbiosis are at increased risk of adverse pregnancy and birth outcomes, including miscarriage, fetal distress, premature rupture of membranes, and preterm delivery.4,7,9

Fortunately, research has been conducted on specific bacteria that, when taken in supplemental form, can contribute to a more healthful vaginal environment. These bacteria include strains of Lactobacillus, which produce lactic acid from the fermentation of glucose, a sugar stored in vaginal epithelial cells. Lactobacilli are the main source of lactic acid in the vagina, and vaginal acidity is important in providing broad protection against undesirable microbes. In fact, keeping vaginal pH acidic reinforces the predominance of lactobacilli to support a balanced vaginal microbial ecosystem more limited in diversity. (It’s important to note that when clinicians talk about gut microbiota, they often think of diversity as beneficial—which is the opposite for vaginal microbiota.)

In addition to lactic acid production, vaginal lactobacilli are thought to limit growth of undesirable microbes in several of the following ways:

• via the production of biosurfactants to disrupt their adhesion to vaginal cells;
• by competing for available nutrients and host surfaces to exclude undesirable microbes;
• through coaggregation with them to impede their ability to colonize the vagina;
• via production of antimicrobial substances to kill them;
• by reinforcing the integrity of the vaginal mucosal epithelial barrier to discourage infection; and
• through the regulation of immune responses to limit their growth.

Today’s Dietitian (TD) sat down with probiotics expert Anthony Thomas, PhD, director of scientific affairs and member of the scientific panel at Jarrow Formulas, a formulator and supplier of nutritional supplements based in Los Angeles, to learn more about the associations between probiotic supplementation and vaginal microbiota.

TD: What does a healthy vaginal microbiota consist of, and what are the most predominant bacterial strains?

Thomas: Having high levels of bacteria from the genus Lactobacillus is generally the hallmark of vaginal health. Most vaginal microbial communities are dominated by one or two Lactobacillus species, representing more than half of all the microbes present within this community. The predominant Lactobacillus species of the vaginal microbiota are L crispatus, L gasseri, L jensenii, and L iners.10 Vaginal microbiotas dominated by L crispatus, L gasseri, or L jensenii are typically associated with health, whereas those dominated by L iners are less stable and more likely to transition to a dysbiotic state.

TD: What are the causes of vaginal dysbiosis, and how does it affect vaginal health?

Thomas: Common factors that influence the composition of the vaginal microbiota and are associated with dysbiosis or BV include douching, increased frequency and number of sexual partners, lack of male circumcision and condom use during intercourse, stress, smoking, hormonal changes (particularly estrogen), and use of antibiotics.

Low levels or absence of vaginal lactobacilli and increased vaginal pH are more often associated with BV, yeast vaginitis, UTIs, increased risk of acquisition of both bacterial and viral STDs, and adverse pregnancy and birth outcomes such as miscarriage, premature rupture of membranes, and preterm birth.

TD: What types of treatments are available for women with dysbiosis or imbalances in vaginal health?

Thomas: BV and UTIs are common and affect tens of millions of women in the United States yearly, with BV as the most common cause of vaginal symptoms among women.11 Antimicrobials have been the primary therapeutic intervention used for the treatment of BV and urogenital infections for over four decades. Unfortunately, it’s often ineffective, particularly for BV, and there’s a high rate of recurrence. Increasing development of antimicrobial resistance is also reducing efficacy.

Antibiotics affect many residential symbiotic bacteria and not just pathogenic bacteria. Many strains of the most prevalent vaginal Lactobacillus species, L cripatus, L gasseri, and L jensenii, are susceptible to commonly used systemic antibiotics, which can be prescribed for various reasons.

Specific Lactobacillus strains can be used for discouraging dysbiosis of the vaginal microbiota and as adjuvant therapies used in conjunction with antimicrobials to improve cure rate and reduce recurrence.12

TD: Which strains of lactobacilli have been clinically validated to promote a balanced vaginal microbial ecosystem? And what is the relationship between these strains and a woman’s vaginal health?

Thomas: Currently, there are only two multistrain probiotic lactobacilli formulations recognized by the Clinical Guide to Probiotic Products Available in USA ( to support women’s vaginal and urinary tract health. These strains have demonstrated antagonism against various common vaginal pathogens and have been shown to be effective at supporting vaginal lactobacilli abundance and acidification when used orally.

One formulation comprises the specific probiotic Lactobacillus strains L rhamnosus GR-1 and L reuteri RC-14, which were isolated from the female urethra.13 The other comprises probiotic strains originally isolated from the vagina of healthy pregnant women and represent the predominant Lactobacillus species associated with health: L crispatus LbV 88, L gasseri LbV 150N, L jensenii LbV 116, and L rhamnosus LbV 96.14

TD: Are women in certain ethnic groups at greater risk of an imbalance, and how does that imbalance lead to health consequences?

Thomas: Black and Hispanic women in the United States have lower rates of a lactobacilli-dominated vaginal microbiota (around 60% to 62%) than white and Asian women (around 80% to 90%), characterized by low levels or absence of lactobacilli and increased diversity of primarily anaerobic bacteria and higher vaginal pH.10 Thus, although this vaginal microbial community can be observed in otherwise healthy women asymptomatic for BV, these women are at increased risk of adverse health outcomes.

TD: How does pregnancy impact the vaginal microbiota, and how can a woman know whether she’s at risk of a vaginal infection?

Thomas: Estrogen plays an important role in promoting a lactobacilli-dominated vaginal microbiota, as it increases the volume of nutrient-containing vaginal secretions as well as thickening of the vaginal mucosal epithelium and accumulation of glycogen—the storage form of the sugar glucose—within these cells. These cells are sloughed off and release their contents, thereby supporting the growth of glucose-fermenting lactobacilli.

So, vaginal microbial communities of pregnant women, who have sustained elevations in estrogen levels, tend to be more stable and have higher relative abundance of lactobacilli. However, pregnant women are still susceptible to acute shifts in their vaginal microbial communities due to lifestyle behaviors, and vaginal microbiota dysbiosis during pregnancy increases risk of adverse pregnancy and birth outcomes.

Odor, discharge, or other factors associated with infection should be monitored. Direct evidence from clinical research demonstrating reduced incidence of infection or adverse outcomes during pregnancy with probiotic use is currently lacking, but this is a therapeutic area of interest among some gynecological researchers, so such direct evidence may accumulate in time. At a minimum, it’s probably worth a woman planning to become pregnant or who is already pregnant to discuss this with her OB/GYN or gynecologist.

TD: Explain how menopause impacts the vaginal microbiota and what women can do to restore balance.

Thomas: Again, estrogen positively influences vaginal lactobacilli abundance. The vaginal microbiota of postmenopausal women is generally characterized by decreased levels of lactobacilli, increased vaginal pH, and microbial diversity more reflective of dysbiosis, in the absence of estrogen replacement therapy.15,16 Clinical symptoms often experienced include vaginal dryness, burning, itching, painful urination and intercourse, increased urinary frequency, and recurrent UTIs. Vaginal estrogen therapy increases vaginal lactobacilli levels and reduces colonization by uropathogenic E coli, thus discouraging UTIs and recurrence.17 Using a validated probiotic to support vaginal lactobacilli levels is likely warranted in this population.

TD: Can probiotic supplementation prevent BV, yeast infections, and adverse obstetric outcomes? If so, how?

Thomas: It’s anticipated, based on currently available scientific evidence, that the specific validated probiotic formulas demonstrated to support vaginal lactobacilli levels and acidification may discourage BV, yeast infections, and adverse obstetric outcomes, but direct evidence is still lacking. Such studies will take time, as they will require many participants observed over extended periods of time. Some evidence supports improved cure rates and reduced relapse for BV and yeast infections when used in combination with conventional antimicrobial therapies.12 I have communicated with gynecological researchers interested in conducting studies to investigate validated vaginal probiotics as preventive therapies, so I suspect more direct evidence will come with time.

TD: How do the beneficial probiotics from a supplement make its way to the vagina to impact its microbiota composition?

Thomas: Bacterial migration from the colon to the vagina occurs naturally, but not by all bacteria. Certain Lactobacillus strains can safely colonize the vagina after oral or vaginal administration, displace and kill pathogens, and modulate host immune responses.18,19 The capacity to survive gastrointestinal transit and migrate from the colon to the vagina is believed to contribute to the efficacy of those probiotic formulations that have been clinically validated to support vaginal and urinary tract health when used orally.

TD: There are hundreds of probiotic supplements on the market today. What probiotic supplements should women take to help prevent and treat BV, yeast infections, and other vaginal issues?

Thomas: Remember, just because it offers a lot of Lactobacillus species in a pink box doesn’t mean it’s a probiotic for women’s health. That’s just marketing. Consumers and health care practitioners should request clinical research evidence from the manufacturer of a given probiotic product marketed for this indication that substantiates this claim. If they cannot provide you manuscripts of clinical research published in reputable scientific journals that demonstrate efficacy for the specific strains used in the probiotic formula for this indication, it is because there is no such evidence.

TD: Which women should take probiotic supplements to maintain vaginal health, and why—and how often?

Thomas: Most women may benefit from taking these supplements. I liken health maintenance to that of car maintenance: Preventive care is best to avoid problems and for operational longevity.

Specific populations may benefit more, such as those at increased risk of vaginal microbiota dysbiosis, including those engaging in the lifestyle behaviors that are associated with diminished vaginal lactobacilli as previously discussed, especially black and Hispanic women, given the lower rates of lactobacilli-dominated vaginal microbiotas observed in these populations. Use of clinically validated probiotic supplements by pregnant women to support vaginal microbial ecosystem balance may be warranted, particularly by those at increased risk of imbalance within the vaginal microbiota, to help safeguard against vaginal microbiota dysbiosis since it’s associated with adverse obstetric outcomes. And these supplements are likely warranted in postmenopausal women not receiving estrogen replacement therapy.

Generally speaking, administered probiotics do not sustainably colonize body surfaces of adult humans, so regular daily use is usually required to maintain the health benefits.

TD: What should consumers look for on the label when purchasing probiotics, and does the type of supplement depend on the vaginal infection or reproductive health issue?

Thomas: A properly labeled probiotic should list the genus, species, and strain for every probiotic organism in the product, as well as the minimum number of live cells or colony forming units per serving when used prior to the “Best Used Before Date” and stored as recommended.

The label should also include usage recommendations, proper storage conditions, and company contact information, or a website to request information or report any problems.

There should be research support for the unique probiotic strains used for a specific indication, so consumers should request research evidence from the company if considering a probiotic product for a desired health benefit.

TD: In what ways can women support vaginal health through diet? For example, would drinking kefir milk or eating kimchi work as well as taking a scientifically proven probiotic supplement?

Thomas: Yogurt containing live active cultures, including lactobacilli (eg, yogurt starter culture L bulgaricus), has been touted as a natural remedy for BV, despite lack of scientific support. In a randomized, double-blinded, placebo-controlled clinical trial, consumption of yogurt fortified with the vaginal probiotic strains L crispatus LbV 88, L gasseri LbV 150N, L jensenii LbV 116, and L rhamnosus LbV 96 significantly improved cure rate and symptoms of BV compared to an acidified yogurt placebo-control, which did contain live active cultures, in women treated with conventional antibiotics.20

Fermented foods containing live active cultures are often mistaken as natural sources of probiotics, but a fermented food is not a source of probiotics unless it contains strain(s) that satisfy the criteria for a probiotic as stipulated in the scientific consensus definition, particularly for conditions beyond general digestive health.

However, this is not to imply fermented foods are not beneficial to human health, as they contribute to general gut health and digestive function. I would speculate that fermented foods containing live active microbial cultures might indirectly support vaginal health if they positively influence composition of the gut microbiota as a reservoir for bacteria that can migrate to the vagina.

TD: What are your thoughts about women eating fermented foods and taking probiotics for added support of vaginal health?

Thomas: Fermented foods, especially those containing live active cultures, have a well-established and long-standing reputation for supporting health. Thus, I think they should be incorporated into most healthful diets. However, as I stated previously, fermented foods containing live active cultures are not necessarily a source of probiotics.

To support vaginal and urinary tract health, I think women should use a probiotic supplement providing the specific strains at a level shown to be efficacious. I am not aware of any fermented foods or beverages that currently provide those probiotic organisms in the United States.

TD: What recommendations can you provide dietitians who are counseling women about their vaginal health and whether probiotics are appropriate?

Thomas: First, know which products are available that contain probiotic strains actually shown to support vaginal health in well-controlled human studies, as these are the only products that are genuine probiotics for this indication. The Clinical Guide to Probiotic Products Available in USA is a good place to start. Currently, the guide acknowledges four probiotic products for this indication: Jarro-Dophilus Women (10 billion/capsule: L crispatus LbV 88, L jensenii LbV 116, L gasseri LbV 150N, L rhamnosus LbV 96), Fem-Dophilus (5 billion/capsule: L rhamnosus GR-1, L reuteri RC-14), RepHresh Pro-B Probiotic (5 billion/capsule: L rhamnosus GR-1, L reuteri RC-14), and UltraFlora Women’s (2 billion/capsule: L rhamnosus GR-1, L reuteri RC-14). It should be noted that three of the four products contain the exact same strains, differing only in live probiotics per dose, which highlights the relative lack of clinical research support for various probiotic Lactobacillus strains to support vaginal and urinary tract health vs gut health.

If the probiotic strain designation is accurately labeled after the bacterial genus and species on a product label, you should be able to find published clinical research that has investigated the health benefits of those strains. So, make sure there’s actual evidence to support the recommendation of a specific probiotic product for vaginal health. If the product does not accurately identify the unique probiotic strains in the product, that should be a red flag.    

Second, evaluate your clients’ individual needs. Do they have a history of BV, UTIs, etc? Do they engage in lifestyle behaviors that may increase their risk of vaginal microbiota dysbiosis? Are they pregnant or postmenopausal? Basically, determine if they can benefit from using a validated probiotic to improve or maintain vaginal health and be ready to make evidence-based recommendations.

— Liz Weiss, MS, RDN, is the voice behind the Liz’s Healthy Table podcast and blog. You can find her at


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