Objective: To assess whether daily ingestion of yogurt containing Lactobacillus acidophilus prevents vulvovaginal candidal infections.

Design: Crossover trial for at least 1 year during which patients were examined for candidal infections and colonizations while receiving either a yogurt-free or a yogurt-containing diet. Patients served as their own controls.

Setting: Ambulatory infectious disease center in a teaching hospital providing tertiary care.

Patients: Thirty-three women with recurrent candidal vaginitis were eligible after recruitment from community practices and clinics and through advertising. Twelve patients were eliminated for protocol violations. Of the remaining 21 patients, 8 who were assigned to the yogurt arm initially refused to enter the control phase 6 months later. Thus, 13 patients completed the protocol.

Interventions: Women ate yogurt for 6 months of the study period.

Measurements: Colonization of lactobacilli and candida in the vagina and rectum; candidal infections of the vagina.

Main results: Thirty-three eligible patients were studied. A threefold decrease in infections was seen when patients consumed yogurt containing Lactobacillus acidophilus. The mean (+/- SD) number of infections per 6 months was 2.54 +/- 1.66 in the control arm and 0.38 +/- 0.51 per 6 months in the yogurt arm (P = 0.001). Candidal colonization decreased from a mean of 3.23 +/- 2.17 per 6 months in the control arm to 0.84 +/- 0.90 per 6 months in the yogurt arm (P = 0.001).

Conclusion: Daily ingestion of 8 ounces of yogurt containing Lactobacillus acidophilus decreased both candidal colonization and infection.