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Yoghurt and vaginal infections

Bandolier is frequently asked the questions 'What is the evidence for X'? A frequently asked question concerns the use of yoghurt for vaginal infections. Where's the evidence? How good is it? We know it works, so why don't you write about it? The answer is usually that there are no systematic reviews (that we can find) and few large, randomised trials. That's about where we are with yoghurt and vaginal infections.

We need to ask three questions:

  1. What is the problem for which we seek an answer?
  2. What is the intervention that might solve the problem?
  3. How do we know when the problem has been solved?

Defining vaginal infection

Bacterial vaginosis is the most common type of vaginal disorder. It is found in about 10% of women and in as many as 30% in selected clinical populations. Perhaps half the women with the disorder have no or mild symptoms. The chief complaints are increased vaginal discharge, especially after coitus or menstruation. This is sometimes accompanied by a fishy odour caused by bacterial breakdown of amino acids. There may be vulvar irritation also.

Treating vaginal infection

A particular feature of bacterial vaginosis is the reduction or absence of lactobacilli in the vaginal flora. Yoghurt (or 'live' yoghurt, anyway) is full of lactobacilli, hence the logic in its use. Other sources of lactobacilli are freeze-dried capsules. The principal is that this restores vaginal lactobacillus and hence pH levels, thus making it difficult for the unwanted organisms and symptoms to persist. Antibiotics are a more conventional way of treating vaginal infection.

Defining a cure

There are a number of standard ways of generating a clinical diagnosis of vaginal infection. They include:
  1. Presence of a whitish discharge.
  2. Vaginal pH above 4.5.
  3. Presence of clue cells on a smear.
  4. Positive test for amines.
If three or more are positive, then vaginosis is present. If there is one or none, then that constitutes a cure.

Searching for evidence

Bandolier did a quick search on the Cochrane Library looking for treatments with yoghurt or lactobacillus-containing products compared with placebo. We found six randomised controlled trials looking at treatment of bacterial infections, and none on yeast infections.

Treating active infection

Four trials looked at intravaginal treatment of a current episode of bacterial vaginosis (Table). Unless otherwise stated, successful treatment was a reduction from three or more bacterial vaginosis clinical criteria reduced to one or none.
Summary of studies of Lactobacillus on treatment of vaginal infection
Reference Clinical Indications and patient characteristics Trial design Intervention Definition of cure Time of measurement Result
Treating active disease      
Fredricsson et al, 1989 84 women with at least 3 of 4 criteria positive Randomised four active treatments 5 mL fermented milk product 5 mL acetic acid jelly 5 mL oestrogen cream 500 mg metronidazole vaginal tablets Two daily doses for 7 days ≤1 criterion 4 weeks 1/13 fermented milk 3/15 acetic acid jelly 1/16 oestrogen cream 13/15 metronidazole
Hallén et al 1992 60 women attending STD clinic with 3 of 4 criteria positive Randomised, double-blind, placebo-controlled Freeze-dried lactobacillus acidophilus capsules versus starch placebo, twice daily for six days ≤1 criterion End of treatment 10/13 Lactobacillus 3/12 placebo
Neri et al, 1993 84 women in 1st trimester, with 3 of 4 criteria positive Randomised comparison with acetic acid tampons 10-15 mL Lactobacillus acidophilus yoghurt two doses for seven days, and repeated one week later Vaginal tampon soaked in 5% acetic acid ≤1 criterion 4 weeks 28/32 yoghurt 12/32 acetic acid
Parent et al, 1996 32 non-menopausal women, 8 of whom were pregnant, with at least 2 of 4 criteria positive Randomised, placebo-controlled Freeze-dried Lactobacillus acidophilus capsules with 30 µg oestradiol versus starch placebo, one to two daily for six days ≤1 criterion Day 15 after start of therapy 16/28 Lactobacillus 0/29 placebo
Reference Clinical Indications and patient characteristics Trial design Intervention Definition of disease Time of measurement Result
Preventing disease recurrence
Reid et al, 1992 41 women with acute lower urinary tract infection Randomised, blinded study Antibiotics followed by freeze dried Lactobacillus Antibiotics followed by sterilized skim milk Twice weekly suppositories for two weeks and then once a month for two months Recurrence of UTI by urine culture Over 6 months 3/14 Lactobacillus 8/17 skim milk
Baerheim et al, 1994 47 women reporting 3 or more episodes of lower urinary tract infection over previous 12 months Randomised, double-blind, placebo-controlled Suppositories of Lactobacillus casei v. rhamnosus or placebo twice weekly for 26 weeks Recurrence of UTI by urine culture and symptoms Over 6 months No difference in infection rates between the two groups.

The results are shown in detail in the Table. Fredricsson and colleagues [1] used a fermented milk product twice daily for seven days in comparison with other treatments, including metronidazole. At 4 weeks, only 1/13 patients had been successfully treated with fermented milk, which compared unfavourably with the antimicrobial metronidazole (13/15 patients successfully treated).

Hallén [2] used lyophilised Lactobacillus acidophilus twice daily for six days. They reported a success rate of 10/13 immediately after treatment compared with 3/12 with placebo. This benefit was almost entirely lost after the next menstrual bleed.

Yoghurt was actually only used in one study [3]. During the first trimester of pregnancy, a regimen of intravaginal yoghurt twice daily for 7 days, with the regimen repeated a week later produced impressive results. On the second day of treatment all 32 yoghurt patients reported subjective feelings of improvement. Using the absence of clinical criteria at one month, 28/32 of the yoghurt group remaining free of bacterial vaginitis, compared with 12/32 treated with acetic acid group.

An open randomised controlled trial [4] of 32 pregnant and non-pregnant women looked at 50-100 mg of a lyophilisate of one selected strain of hydrogen peroxide-producing Lactobacillus acidophilus plus 0.03 mg of oestriol daily. Entry criteria were less strict, with a minimum of two of four clinical criteria present instead of the usual three. At two weeks lactobacillus was significantly more effective than placebo with 16/28 cured with lactobacillus compared with 0/29 with placebo.

Preventing reinfection

Two trials looked at whether lactobacillus is useful in preventing recurrence of infection, though the concentration was on urinary tract infection, rather than just vaginal infection.

One trial [5] looked at lactobacillus treatment to prevent recurrence of urinary tract infection (UTI) after antimicrobial treatment of UTI with an antibiotic. Women were randomised to use lactobacillus suppositories or a sterilised skimmed milk placebo twice weekly for two weeks, then once monthly for two months. Recurrence rates were collected over 6 months. With lactobacillus 21% (3/14) had a recurrence compared with 47% (8/17) with placebo.

Another trial [6] followed women who suffered frequent UTIs over a 6-month period. During this time women had twice weekly doses of Lactobacilli casei v. rhamnosus or placebo. There was no statistically significant difference in monthly infection rates, which were 0.21 (95% CI 0.15 to 0.28) for lactobacillus and 0.15 (0.09 to 0.21) for placebo.

Adverse effects

Two trials reported on adverse effects with lactobacilli suppositories. In both cases there were no serious side effects. One trial [4] reported one case of disagreeable and burning sensations with active treatment. The second trial [6] reported messy discharge in four actives and one control.

The bottom line

The bottom line is that these trials do not constitute enough evidence to recommend using yoghurt or Lactobacillus to cure vaginal infections. At best they may have some effect in ameliorating symptoms of bacterial vaginosis. The negative trial [1] looked at the outcome three weeks after the end of treatment. Other studies used endpoints much closer to the end of treatment, and were positive.

For suppressing urinary tract infections, there is no evidence of any effect.


  1. B Fredricsson, K Englund, L Weintraub, A Olund, C Nord. Bacterial vaginosis is not a simple ecological disorder. Gynecol Obstet Invest. 1989 28: 156-60.
  2. A Hallén, C Jarstrand, C Pahlson. Treatment of bacterial vaginosis with lactobacilli. Sex Transm Dis. 1992 19: 146-8.
  3. A Neri, G Sabah, Z Samra. Bacterial vaginosis in pregnancy treated with yoghurt. Acta Obstet Gynecol Scand. 1993 72: 17-9.
  4. D Parent et al. Therapy of bacterial vaginosis using exogenously-applied Lactobacilli acidophili and a low dose of estriol: a placebo-controlled multicentric clinical trial. Arzneimittelforschung. 1996 46: 68-73.
  5. G Reid, A Bruce, M Taylor. Influence of three-day antimicrobial therapy and lactobacillus vaginal suppositories on recurrence of urinary tract infections. Clin Ther. 1992 14: 11-6.
  6. A Baerheim, E Larsen, A Digranes. Vaginal application of lactobacilli in the prophylaxis of recurrent lower urinary tract infection in women. Scand J Prim Health Care. 1994 12: 239-43.

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