Clinical trials have examined whether probiotics taken orally can influence vaginal floral balance and, likewise, whether all probiotics have such benefits. The answer to the first issue is that, yes, an intake of probiotics as an oral supplement can significantly and beneficially affect the balance of vaginal flora. However, the answer to the second issue is that only certain probiotics can provide this benefit. Direct comparisons have demonstrated that the probiotic species and strains must be carefully selected in order to significantly and beneficially influence vaginal health.
The major criteria required in selecting beneficial probiotics are their ability to colonize the vagina and reduce undesirable vaginal microflora. In one trial, GR-1 and RC-14 administered in skim milk were given orally to 10 women twice daily for 14 days. GR-1 and RC-14 were recovered from the vagina and identified by morphology and molecular typing within 1 week of commencement of the trial. In another randomized, placebo-controlled trial, GR-1 and RC-14 were given to 64 women for 60 days. Microscopy analysis showed the restoration of healthy vaginal flora level in 37% of women taking GR-1 and RC-14 vs. 13% in subjects in placebo group. Other trials have also confirmed the benefits of GR-1 and RC-14 intake.
In order for a probiotic to be effective, of course, significant numbers of live bacteria (indicated as Colony Forming Units or CFU) must survive when the probiotic is taken by mouth. Tests for the gastrointestinal survivability of strains have shown good results. GR-1 and RC-14 are bile tolerant and survive passage through the gastrointestinal tract. This in vivo result confirms what might be expected from test tube research. For instance, an in vitro study has shown that RC-1 4 and GR-1 are tolerant to 0.3 and 0.5 percent (w/v) bile, respectively. According to the experts, both strains can therefore be considered both acid and bile tolerant given that a concentration of 0.3 percent is considered physiologically relevant.
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