Cranberry

Effectiveness of Cranberry Capsules to Prevent Urinary Tract Infections in Vulnerable Older Persons: A Double-Blind Randomized Placebo-Controlled Trial in Long-Term Care Facilities

Study: A 2014 double-blind, randomized, placebo-controlled multicenter trial (N=928, 703 women, median age 84) in long-term care facilities (LTCFs). Participants took cranberry capsules or placebo twice daily for 12 months. They were stratified by UTI risk (high risk: long-term catheterization, diabetes mellitus, or ≥1 UTI in the preceding year). Outcomes were incidence of UTI using clinical (symptoms-based) and strict (culture-verified) definitions.

Findings: In high-UTI-risk participants (n=516), cranberry capsules reduced clinically defined UTI incidence (62.8 vs. 84.8 per 100 person-years, P=0.04; treatment effect 0.74, 95% CI 0.57–0.97). No significant reduction was seen with the strict definition (treatment effect 1.02, 95% CI 0.68–1.55) or in low-UTI-risk participants (n=412). Side effects were uncommon, primarily mild gastrointestinal (e.g., abdominal discomfort), and similar to placebo. No serious adverse events were linked to cranberry.

Link: PMC - Effectiveness of Cranberry Capsules in LTCFs

High Dose Versus Low Dose Standardized Cranberry Proanthocyanidin Extract for the Prevention of Recurrent Urinary Tract Infection in Healthy Women: A Double-Blind Randomized Controlled Trial

Study: A 2021 randomized, double-blind, controlled trial (PACCANN, NCT02572895) at the Institute of Nutrition and Functional Foods, Laval University, involving 145 healthy women with recurrent UTIs (≥2 in past 6 months or ≥3 in past 12 months). Participants received high-dose cranberry proanthocyanidins (PACs, 2×18.5 mg daily, n=72) or low-dose control (2×1 mg daily, n=73) for 24 weeks. The primary outcome was the mean number of new symptomatic UTIs.

Findings: High-dose cranberry PACs significantly reduced symptomatic UTIs compared to the low-dose control (P<0.05). Secondary outcomes (symptomatic UTI with pyuria or bacteriuria) also favored the high-dose group. Side effects were mild, mainly gastrointestinal (e.g., diarrhea, nausea), with no significant difference between groups. Compliance was high, and no serious adverse events were reported.

Link: PMC - High Dose vs. Low Dose Cranberry Extract

Cranberry Juice Fails to Prevent Recurrent Urinary Tract Infection: Results From a Randomized Placebo-Controlled Trial

Study: A 2011 double-blind, placebo-controlled trial (NCT01033383) involving 319 college women with an acute UTI, followed for 6 months or until a second UTI. Participants drank 8 oz of 27% cranberry juice or placebo twice daily. The study aimed to detect a 2-fold difference in UTI recurrence.

Findings: The recurrence rate was 16.9% overall, with no significant difference between cranberry (20.0%) and placebo (14.0%) groups. No reduction in urinary symptoms was observed at 3 days, 1–2 weeks, or ≥1 month. Side effects included mild gastrointestinal upset (e.g., diarrhea), similar in both groups. The study suggested cranberry juice may not be effective for UTI prevention in this population.

Link: OUP - Cranberry Juice Fails to Prevent UTI

A Randomized Clinical Trial to Evaluate the Preventive Effect of Cranberry Juice (UR65) for Patients with Recurrent Urinary Tract Infection

Study: A 2013 randomized, placebo-controlled trial in Japan evaluating cranberry juice (UR65) in women with recurrent UTIs. Participants consumed cranberry juice or placebo for an unspecified duration, with outcomes focused on UTI relapse rates.

Findings: Cranberry juice significantly reduced UTI incidence (weighted risk ratio 0.6750, 95% CI 0.5516–0.7965, P<0.0001), particularly against P-fimbriated E. coli strains. Subgroup analysis showed greater benefits in women with recurrent UTIs. Side effects were minimal, primarily mild gastrointestinal (e.g., stomach upset), with no serious adverse events reported.

Link: ScienceDirect - Cranberry Juice for UTI Prevention

Effects of a Supplement Containing a Cranberry Extract on Recurrent Urinary Tract Infections and Intestinal Microbiota: A Prospective, Uncontrolled Clinical Study

Study: A 2022 prospective, uncontrolled trial (NCT03019874) at Charité—Universitätsmedizin Berlin, involving women aged 18–70 with chronic recurrent UTIs (≥3 per year or ≥2 in 6 months). Participants took a cranberry extract supplement for 6 months. Outcomes included UTI incidence and gut microbiota changes, with fecal samples analyzed at baseline, 3 months, and 6 months.

Findings: Cranberry extract reduced UTI incidence compared to baseline, though the lack of a placebo group limits conclusions. A slight, non-significant decrease in the Bacteroidetes–Firmicutes ratio was observed, suggesting potential microbiota modulation. Side effects were mild, primarily gastrointestinal (e.g., nausea, diarrhea), with no serious adverse events.

Link: Liebert - Cranberry Extract and Microbiota

Cranberry Supplements for Urinary Tract Infection Prophylaxis in Pregnant Women: A Systematic Review of Clinical Trials and Observational Studies

Study: A 2023 systematic review of two RCTs and one nested cohort study, involving 1,156 pregnant women. Studies evaluated cranberry supplements (juice or capsules) for UTI prevention, focusing on efficacy, acceptability, and feasibility. The review followed PRISMA guidelines and assessed risk of bias.

Findings: Efficacy data were inconclusive due to high dropout rates (39–49%) and low recruitment (33% average). Cranberry juice had a 23% withdrawal rate due to side effects (e.g., gastrointestinal discomfort, taste issues), while capsules were better tolerated (2% withdrawal due to impaired appetite). No significant safety concerns were reported, but efficacy in pregnant women remains uncertain due to study limitations.

Link: PMC - Cranberry in Pregnant Women