Abstract
PurposeOur objective was to assess the efficacy of a high dose cranberry proanthocyanidin extract for the prevention of recurrent urinary tract infection.Material and methodsWe recruited 145 healthy, adult women with a history of recurrent urinary tract infection, defined as ≥ 2 in the past 6 months or ≥ 3 in the past 12 months in this randomized, controlled, double-blind clinical trial. Participants were randomized to receive a high dose of standardized, commercially available cranberry proanthocyanidins (2 × 18.5 mg daily, n = 72) or a control low dose (2 × 1 mg daily, n = 73) for a 24-week period. During follow-up, symptomatic women provided urine samples for detection of pyuria and/or bacteriuria and received an appropriate antibiotic prescription. The primary outcome for the trial was the mean number of new symptomatic urinary tract infections during a 24-week intervention period. Secondary outcomes included symptomatic urinary tract infection with pyuria or bacteriuria.ResultsIn response to the intervention, a non-significant 24% decrease in the number of symptomatic urinary tract infections was observed between groups (Incidence rate ratio 0.76, 95%CI 0.51–1.11). Post-hoc analyses indicated that among 97 women who experienced less than 5 infections in the year preceding enrolment, the high dose was associated with a significant decrease in the number of symptomatic urinary tract infections reported compared to the low dose (age-adjusted incidence rate ratio 0.57, 95%CI 0.33–0.99). No major side effects were reported.ConclusionHigh dose twice daily proanthocyanidin extract was not associated with a reduction in the number of symptomatic urinary tract infections when compared to a low dose proanthocyanidin extract. Our post-hoc results reveal that this high dose of proanthocyanidins may have a preventive impact on symptomatic urinary tract infection recurrence in women who experienced less than 5 infections per year.Trial registration: Clinicaltrials.gov, identifier NCT02572895
Highlights
Urinary tract infection (UTI) is one of the main reasons for emergency medical consultation
Post-hoc analyses indicated that among 97 women who experienced less than 5 infections in the year preceding enrolment, the high dose was associated with a significant decrease in the number of symptomatic urinary tract infections reported compared to the low dose
Our results indicate that the intake of 2 × 18.5 mg PACs daily was associated with a non-statistically significant 24% reduction in the risk of symptomatic UTI compared to a daily dose of 2 × 1 mg PACs during a 24-week follow-up period, similar to the results of a recent meta-analysis [16]
Summary
Urinary tract infection (UTI) is one of the main reasons for emergency medical consultation. Clinical trials have been conducted to test the efficacy of cranberry products, mainly in the form of juices, but their results remain discordant [3]. This discrepancy is mainly explained by a lack of compliance, lack of statistical power and variable PAC concentrations in the tested products. According to ex vivo clinical studies (dose–effect studies evaluating the optimal dose for urine anti-adhesion effect), the quantification of PACs requires standardized, reproducible methods and should be at least 36 mg/ day [5, 6]. We hypothesize that the efficacy of cranberry products on the prevention of recurrent UTIs in women could be improved with the use of an optimal PACs dose (standardized at 2 × 18.5 mg/day)
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