Can a probiotic swallowed by mouth influence bacteria living in the vagina?

A new randomised trial suggests that the answer may be yes—at least for one particular strain, in one particular group of healthy women, over one particular 12-week period.

Researchers studying oral probiotics and vaginal health gave women either a placebo or Lactiplantibacillus plantarum Probio87. The probiotic group experienced a greater reduction in Nugent score, a laboratory measure used to assess patterns of vaginal bacteria. Researchers also observed changes in both vaginal and intestinal microbial communities.

That is encouraging. It is not proof that probiotics generally treat bacterial vaginosis, thrush, sexually transmitted infections or every itch that has ever caused someone to conduct a worried search at 2 am.

The best-friend pharmacist version is simple: interesting strain-specific research, sensible curiosity and no miracle knickers required.

Why does the vaginal microbiome matter?

The vagina contains its own community of microorganisms. In many healthy women, bacteria belonging to the Lactobacillus group are prominent.

These bacteria can help maintain an acidic vaginal environment and make conditions less comfortable for some potentially troublesome organisms. The composition of the vaginal microbiome may be influenced by:

• age;
• hormonal changes;
• menstruation;
• pregnancy;
• menopause;
• sexual activity;
• antibiotic use;
• vaginal products; and
• individual biology.

A healthy vaginal microbiome is not identical in every woman. The goal is not to collect one fashionable bacterium and evict every other microscopic resident with a clipboard.

Researchers are nevertheless interested in whether carefully selected oral probiotics and vaginal health may be connected through what is often called the gut–vaginal axis.

What is the gut–vaginal axis?

The gut–vaginal axis is a developing area of research examining possible connections between intestinal and vaginal microbial ecosystems.

Scientists have proposed several possible routes through which an oral probiotic might influence vaginal bacteria:

• temporary survival and activity within the intestine;
• interaction with immune signalling;
• production of microbial metabolites;
• effects on competing intestinal microorganisms; and
• movement of suitable organisms from the intestinal and perineal region to the vaginal environment.

These possibilities are biologically interesting, but this trial did not establish exactly how Probio87 produced the observed changes.

The sachet did not pack a tiny suitcase, announce that it was moving south and provide the researchers with a forwarding address.

What did the trial involve?

The study was a randomised, double-blind, placebo-controlled trial conducted in Malaysia.

Researchers enrolled 112 generally healthy women between the ages of 18 and 80. Participants did not have a diagnosed urogenital infection and entered the trial with a Nugent score below 7.

The women were assigned to receive:

• Probiotic: one daily sachet containing approximately one billion colony-forming units—10⁹ CFU—of Lactiplantibacillus plantarum Probio87; or
• Placebo: an identical-looking sachet containing the carrier material without live Probio87.

Both products were dissolved in room-temperature water and consumed once daily for 12 weeks.

Women who were pregnant, had a urogenital infection, had recently used certain vaginal or hormonal therapies, took long-term medicines for chronic illness or had recently undergone pelvic or gynaecological surgery were excluded.

This matters when interpreting oral probiotics and vaginal health: the participants were comparatively healthy and the results cannot automatically be transferred to pregnant women, medically complex patients or women seeking treatment for active symptoms.

What is a Nugent score?

The Nugent score is calculated by examining a Gram-stained vaginal sample under a microscope. The observer assesses bacterial shapes associated with lactobacilli and bacteria commonly found in bacterial vaginosis.

The score ranges from 0 to 10:

• 0–3: generally consistent with a Lactobacillus-dominant pattern;
• 4–6: considered an intermediate pattern; and
• 7–10: consistent with bacterial vaginosis.

A Nugent score is a laboratory measure. It is not a complete assessment of symptoms, sexual health, comfort, reproductive health or general wellbeing.

It is also not a vaginal Fitbit score. A lower number does not mean that every aspect of health has suddenly earned a gold star.

What do the results mean for oral probiotics and vaginal health?

Paired vaginal results were available for 104 women: 53 in the probiotic group and 51 in the placebo group.

At the beginning, average scores were similar:

• 4.08 in the probiotic group; and
• 4.10 in the placebo group.

After 12 weeks, the average scores were:

• 2.72 in the probiotic group; and
• 3.27 in the placebo group.

The average reduction was 1.36 points with Probio87 and 0.82 points with placebo. The difference in change between groups was statistically significant.

In other words, both groups improved, but the probiotic group improved by roughly half a point more.

That result supports further investigation of oral probiotics and vaginal health. However, all participants began without bacterial vaginosis. A statistically significant change in a laboratory score does not prove that an infection was cured, symptoms were relieved or future illness was prevented.

This is the central caution when discussing oral probiotics and vaginal health: a promising microbial marker is not automatically a proven clinical benefit.

What happened to the vaginal bacteria?

The researchers used 16S ribosomal RNA sequencing to examine the relative composition of bacterial communities.

In the probiotic group, the researchers reported patterns consistent with maintaining Lactobacillales while limiting the appearance or relative abundance of several taxa associated with bacterial vaginosis or microbial imbalance.

For example, Gardnerella was part of the study’s defined core vaginal microbiome in the probiotic group at baseline but was no longer identified as a core member after 12 weeks. Lactobacillales remained part of the core community.

The placebo group showed a different pattern, including the appearance of several potentially less favourable taxa within the defined core microbiome.

These are ecological observations. Sequencing tells us about relative bacterial patterns; it does not prove what every organism was doing, whether it caused a symptom or whether it would eventually cause disease.

Microbiome graphs are fascinating, but the coloured columns do occasionally behave as though they have been invited to make clinical decisions beyond their pay grade.

What happened in the gut?

Paired faecal samples were available for 108 women.

The probiotic group showed changes in intestinal microbial richness and evenness, with increases in several genera associated with short-chain fatty-acid production.

Short-chain fatty acids are microbial metabolites involved in intestinal biology, barrier function and communication with the host.

However, the trial inferred potential short-chain fatty-acid production from which bacteria were present. It did not directly measure those metabolites or prove that they caused the vaginal findings.

The study therefore supports an association between selected oral probiotics and vaginal health markers. It does not yet provide a complete map of the road connecting the two.

Future research into oral probiotics and vaginal health will need to connect these bacterial patterns with directly measured metabolites, symptoms and longer-term clinical outcomes.

Were there any side effects?

The researchers reported no adverse effects or complications during the 12-week study.

That is reassuring, but it should be kept in proportion. This was a modest-sized trial involving selected healthy women. It cannot establish safety for every person, every probiotic product, pregnancy, serious illness or weakened immune function.

“No adverse effects reported in this study” is the accurate sentence. “Probiotics can never cause a problem” is the sentence that has wandered off without its pharmacist.

Important limitations of the study

The randomised, double-blind, placebo-controlled design is a genuine strength. Several limitations still matter:

• The study involved healthy women without bacterial vaginosis or another urogenital infection.
• It did not test treatment of vaginal symptoms or diagnosed disease.
• The intervention lasted 12 weeks, with no long-term follow-up showing whether the changes persisted.
• Complete paired vaginal samples were available for 104 of the 112 randomised participants.
• The microbiome analysis measured relative bacterial composition rather than direct microbial function.
• Metabolites such as short-chain fatty acids were predicted from bacterial patterns rather than measured directly.
• The analysis did not report effect sizes or confidence intervals, limiting interpretation of the magnitude and precision of the result.
• The study was conducted in one Malaysian research setting, which may limit generalisation to other populations.
• Hormonal stage, menstrual status and age may influence vaginal bacteria, yet the trial covered a very wide age range.
• The results apply to Probio87 at the tested dose and cannot be assigned automatically to other strains or products.

The probiotic and placebo sachets were supplied by Probionic Corp., and the research was supported by a USM–Probionic grant. The authors declared no conflicts of interest.

Commercial support does not automatically invalidate a study. It does mean the relationship belongs in the article where readers can see it—not folded into a tiny footnote and placed behind a decorative fern.

Does this prove that oral probiotics treat bacterial vaginosis?

No.

Bacterial vaginosis is a recognised vaginal condition that may cause a thin greyish-white discharge and a noticeable fishy odour, although some women have no symptoms.

The women in this trial did not have bacterial vaginosis at enrolment. The trial cannot tell us whether Probio87 would cure an active episode, prevent recurrence or perform as well as established treatment.

Current clinical guidance does not support replacing recommended bacterial vaginosis treatment with an over-the-counter probiotic. Symptomatic bacterial vaginosis is normally assessed and treated with suitable prescribed antibiotics.

Research into oral probiotics and vaginal health may eventually help refine prevention or supportive-care strategies. For now, your probiotic should not dismiss your doctor, confiscate the prescription and announce that it has everything under control.

What oral probiotics and vaginal health research has not established

This trial does not prove that Probio87—or probiotics generally—can:

• treat bacterial vaginosis;
• treat vaginal thrush;
• treat urinary tract infections;
• treat or prevent sexually transmitted infections;
• relieve vaginal discharge, itching, odour or pain;
• improve fertility or pregnancy outcomes;
• prevent future vaginal dysbiosis;
• replace antibiotics, antifungals or professional assessment; or
• produce the same results when a different strain or formulation is used.

Lactiplantibacillus plantarum is a species. Probio87 is the specific strain studied.

The word “probiotic” is a broad job category, not a guarantee that every bacterial cousin arrived with the same qualifications.

Everyday vaginal care without the scented circus

The vagina is a self-regulating biological environment. It generally does not require internal washing, deodorising or a tropical-fruit fragrance strong enough to summon wildlife.

Sensible habits include:

• wash the external genital area gently with water or a mild, unscented cleanser if tolerated;
• avoid vaginal douching;
• avoid inserting yoghurt, household remedies or unapproved products;
• change out of wet clothing when practical;
• use breathable underwear if it feels more comfortable;
• follow prescribed treatment exactly;
• discuss recurrent symptoms with a healthcare professional; and
• consider appropriate STI testing when relevant.

Please do not put yoghurt inside the vagina because somebody on social media called it “natural”. Potatoes are also natural. We are not inserting those either.

When vaginal symptoms need proper assessment

Arrange an assessment with a doctor, sexual-health professional or pharmacist if you experience:

• a new or unusual vaginal discharge;
• a strong or fishy odour;
• persistent itching, burning or irritation;
• pain during urination or sex;
• pelvic or lower-abdominal pain;
• fever or feeling acutely unwell;
• bleeding after sex or unexpected vaginal bleeding;
• repeated episodes after treatment;
• possible exposure to a sexually transmitted infection; or
• symptoms during pregnancy.

Bacterial vaginosis, thrush, sexually transmitted infections, urinary infections, dermatitis and hormonal changes can produce overlapping symptoms. A vagina is not obliged to reveal the diagnosis through interpretive dance.

Using the wrong treatment may delay proper care or make irritation worse.

Where do Noster ProBiotics fit?

Noster ProBiotics are refrigerated live culture probiotics intended to support everyday gut and microbial balance.

Noster ProBiotics and their formulation were not tested in this trial. We therefore do not claim that Noster will reproduce the Nugent-score or microbiome findings reported for Probio87.

Noster ProBiotics are not treatments for bacterial vaginosis, vaginal thrush, urinary infections or sexually transmitted infections. They should not replace examination, testing or prescribed treatment when symptoms are present.

The study is relevant to Noster because it adds to the developing research around oral probiotics and vaginal health and reminds us that microbial communities in different parts of the body may communicate.

Responsible communication about oral probiotics and vaginal health must remain strain-specific and must distinguish microbial support from treatment of a diagnosed condition.

It does not give us permission to borrow another strain’s research and glue it onto our bottle with ambitious enthusiasm.

If your goal is general digestive and microbial support, you can learn more about Noster Live Culture Probiotic Capsules.

Pop it in the fridge. Take it daily. Let your pharmacist keep the promises sensible.

Frequently asked questions

Can an oral probiotic really affect vaginal bacteria?

This trial found changes in vaginal bacterial patterns after women took one specific oral strain for 12 weeks. The precise route connecting the intestinal and vaginal ecosystems was not established, and the finding cannot be generalised automatically to every probiotic.

Did the probiotic treat bacterial vaginosis?

No. Participants were healthy and had Nugent scores below the diagnostic range for bacterial vaginosis at enrolment. The study examined changes in laboratory and microbiome markers, not treatment of active bacterial vaginosis.

What does a lower Nugent score mean?

A lower score generally reflects a bacterial pattern containing more Lactobacillus-like organisms and fewer bacterial forms associated with bacterial vaginosis. It is a laboratory measure and does not by itself prove that symptoms, infection risk or long-term health improved.

Can probiotics treat vaginal thrush?

This trial did not investigate treatment of vaginal thrush. Thrush is caused by fungal overgrowth and requires an appropriate diagnosis and, when necessary, antifungal treatment.

Should I put probiotic yoghurt in the vagina?

No. Food products are not manufactured as sterile vaginal medicines and may contain unsuitable ingredients or organisms. Use only products specifically intended for vaginal use and recommended by a qualified healthcare professional.

Was Noster ProBiotics tested in this study?

No. The trial tested Lactiplantibacillus plantarum Probio87 at a particular dose. Noster ProBiotics cannot claim the same results unless the Noster formulation is studied directly.

Are probiotics safe for every woman?

Probiotics are generally well tolerated by many healthy adults, but safety depends on the organism, product and individual. Pregnant women, people with weakened immune systems or serious illness, and anyone using probiotics for persistent symptoms should obtain professional advice.

The friendly pharmacist’s final word

This trial offers an encouraging piece of evidence about oral probiotics and vaginal health.

After 12 weeks, healthy women taking one specific strain experienced a greater reduction in Nugent score than those receiving placebo. Researchers also observed different bacterial patterns in vaginal and faecal samples, and no adverse effects were reported.

But the participants did not have bacterial vaginosis, the additional improvement was modest, microbial function was not measured directly and the trial was commercially supported.

The correct conclusion is therefore:

One oral probiotic strain changed selected vaginal and intestinal microbial markers in healthy women. That is promising evidence for further study—not proof that probiotics generally treat vaginal disease.

Your gut and vagina may be on speaking terms. We are still learning what they discuss, and it would be impolite for a supplement label to invent the minutes of the meeting.

Resources

• 2026 randomised trial: Probio87 and gut–vaginal microbiota in healthy women
• Molecular Nutrition & Food Research: Study publication record
• CDC: Bacterial vaginosis treatment guidance
• NHS: Bacterial vaginosis symptoms and treatment
• NCCIH: Probiotic usefulness and safety

This article provides general educational information and does not replace individual advice, examination or treatment from your doctor, pharmacist or sexual-health professional.