#84 Cranberry Juice/Tablets for the Prevention of Urinary Tract Infection: Naturally the Best?

CLINICAL QUESTION

Does cranberry juice or extract prevent recurrent urinary tract infections (UTI)?

BOTTOM LINE

Available evidence for cranberry products for reduction of UTIs is poor and inconsistent. Funding or selective reporting influence the few positive results.

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EVIDENCE

Two systematic reviews^1,2 and 5 randomized controlled trials (RCTs),^3-7 in mostly female patients followed ~6 months

Cochrane:¹ 24 RCTs (13 RCTs with juice/concentrate, 10 tablets/capsules and 1 both), 4473 patients
- 13 RCTs meta-analyzed:
  - No significant difference in number of patients getting >1 UTI, relative risk (RR) 0.86 (0.71-1.04)
  - No difference in subgroups (recurrent UTI, elderly, catheterized, pregnant, or children).
- Studies not meta-analyzed: 8 found no benefit, ² found benefit
- RCTs at high risk of bias: For example, 75% of RCTs excluded patients from analysis and 46% lost >20% of patients.
Archives:² 13 RCTs (8 RCTs of juice/concentrate, 4 tablets/capsules, and 1 both), 1616 patients
- Statistically significant reduction in UTIs, RR 0.62 (0.49-0.80), number needed to treat (NNT)=12 to avoid recurrent UTI
  - Excluded one negative outlier trial but included the one positive outlier trial. If positive outlier excluded, results no longer significant
- Issues: Poorer quality literature search, poor-quality RCTs (as above), and selective analysis.
3 RCTs of women with recurrent UTI:
- 176 patients:³ No difference in UTI (cranberry juice 27.5%, placebo 30.4%, p=0.70)
- 213 patients:⁴ No difference in UTI (cranberry juice 29.9%, placebo 35.8%, p=0.13)
- 373 patients:⁵ Statistically significant reduction in UTI
  - Cranberry juice 18%, placebo 27%, NNT=12.
- A cranberry juice manufacturer sponsored the only RCT of the three with positive results (the others were not industry sponsored).

Context:

Proposed active ingredient in cranberry (A-type proanthocyanidins) is believed to inhibit adherence of Escherichia coli to the urogenital mucosa.^1,2Clinically unproven.
Cranberry juice/cocktail costs ~$0.45-0.66 and contains 120-150 Calories per 250 mL
- Assuming 2 cups/day and the most positive data:^2,5One in 12 chance of avoiding UTI over 6 months would cost ~$180 and ~45,000 Calories (5.8 kg potential weight gain).
Cranberry products likely inferior to antibiotics
- RCT of 221 women with recurrent UTI: Statistically significant more UTIs over 12 months for cranberry capsules (4/woman) versus trimethoprim-sulfamethoxazole (1.8/woman).⁶