Efficacy of a standardized cranberry supplement on overactive bladder symptoms and urobiome alterations in young women: a randomized, double-blind, placebo-controlled pilot trial

Introduction Urobiome dysbiosis has been implicated in the pathogenesis of overactive bladder (OAB). In this study, the efficacy of a cranberry supplement for OAB symptoms was investigated, and concurrent urobiome alterations were evaluated in young women. Methods This double-blind, randomized, placebo-controlled trial enrolled 26 women (median age, 23 years) with OAB (Overactive Bladder Symptom Score [OABSS] ≥ 3), who received either a cranberry supplement (36 mg proanthocyanidins per day) or placebo for 4 weeks. Clinical efficacy was assessed using the OABSS reduction rate, and urobiome composition was evaluated by 16S rRNA gene sequencing. Results Twenty-five participants were included in the analysis. At 4 weeks, the OABSS reduction rate was greater in the cranberry group than in the placebo group (median, 66.7% vs. 40.0%; p = 0.039). At baseline, the urobiome was dominated by Lactobacillus (median relative abundance, 64.2%). After cranberry supplementation, the relative abundance of Lactobacillus decreased within the cranberry group (median change, −4.39%; p = 0.027; q = 0.096). No compositional changes were observed in the placebo group. Conclusions Cranberry supplementation was associated with greater improvement in OAB symptoms than was observed with placebo in young women, while a decrease in Lactobacillus relative abundance was observed within the cranberry group. Given the small sample size of this exploratory pilot trial and the limited species-level resolution of 16S rRNA sequencing, these concurrent findings should be regarded as hypothesis-generating and warrant further investigation. Clinical trial registration https://www.umin.ac.jp/ctr/ , identifier UMIN000057544.