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Lactic acid – the key to a healthy vagina

Research 13 Nov 2018

Women are at greater risk of sexually transmissible infections (STIs) and, in turn, problems with their reproductive health if their vagina doesn't have high amounts of lactic acid, according to a recent review published in the journal Research in Microbiology.

A healthy vagina needs to have certain types of the bacteria lactobacillus, which produce high levels of lactic acid. The study found this lactobacillus make the vagina acidic, which is important in helping to prevent a condition known as bacterial vaginosis (BV).

BV is a bacterial infection of the vagina that occurs when its normal balance of bacteria changes. The main symptoms of BV are a white discharge and a strong fishy odour, but half of cases show no symptoms. These cases can only be diagnosed with a vaginal examination by your doctor.

BV can increase a woman's risk of catching STIs – such as gonorrhoea, chlamydia, herpes and HIV – and has also been linked to an increased risk of pelvic inflammatory disease (PID), early pregnancy loss, premature delivery and low birth weight of babies.

In Australia, BV affects up to 12% of women, but up to 30% of women in higher-risk groups such as indigenous communities. It can be due to reasons such as:

  • a change in sexual partner
  • washing the vagina (douching) with soap or another product
  • smoking.

The review – which involved the review of 142 studies – looked at the role of lactobacillus in vaginal health, including the prevention and treatment of BV. It found that 'beneficial' lactobacillus appeared to improve the health of the vagina, most likely due to the lactic acid's ability to kill harmful bacteria.

Undertaken by a team of researchers from Australian institutions, and John Hopkins University in the United States, the review sheds further light on the connection between the human body and the 39 trillion bacteria living in it. The bacteria – called the microbiome – live in various parts of the body including the gut, mouth, skin, nose, throat, urethra, vagina and penis.

"Studies … in this review demonstrate the importance of a stable vaginal microbiome for a woman's health," said Professor Gilda Tachedjian, the lead author of the review and the Head of Life Sciences Discipline at the Burnet Institute.

"Unlike the gut, where a diverse range of bacteria is beneficial, the vagina is most stable with a microbiome dominated mainly by favourable lactobacillus," she said.

The current recommended treatment for BV is antibiotics. However, several studies have examined the use of probiotics for treating BV.

While some of these studies appeared to show a positive effect, Prof Tachedjian said that, overall, there has not been enough to show consistent benefit of lactobacillus-based probiotics. "Better designed clinical trials" were now needed to prove their benefits for treating or preventing BV.

In the meantime, she said, her team was focusing their work on creating vaginal gels containing lactic acid for women with BV. "We are at an exciting stage of discovery," said Prof Tachedjian.

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Last updated: 
18 January 2024
Last reviewed: 
24 May 2024