This systematic review examines whether cranberry products can effectively prevent urinary tract infections (UTIs). Cranberries contain proanthocyanidins (PACs), which prevent Escherichia coli from attaching to the bladder mucosa, which could reduce the development of infections.
The analysis included 50 randomized controlled trials with a total of 8,857 participants. The results show that cranberry products reduce the risk of symptomatic, culture-confirmed urinary tract infections in women with recurrent UTIs, children and people at increased risk after medical procedures. In contrast, there is no clear evidence of benefit in older people, pregnant women or people with neurological bladder dysfunction.
Conclusion: Cranberries may be beneficial for certain risk groups, but further standardized studies are needed to make clear recommendations.
Background:
Urinary tract infections (UTIs) are among the most common bacterial infections worldwide and particularly affect women, children and people with an increased risk of infection, e.g. after medical procedures. Antibiotics are the standard treatment, but the increasing development of resistance requires alternative prevention strategies. Cranberries contain proanthocyanidins (PACs), which inhibit the attachment of Escherichia coli to urinary tract cells and could thus prevent infections.
Aims of the study:
This Cochrane review analyzes the effectiveness of cranberry products (juice, tablets, capsules) for the prevention of urinary tract infections in different risk groups and compares them with placebo, no treatment, antibiotics or probiotics.
Methodology:
– 50 randomized controlled trials (RCTs) with 8,857 participants were included.
– The data comes from several databases, including MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials.
– The primary endpoints were the occurrence of symptomatic, culture-confirmed HWIs, adverse events and treatment adherence.
– The evidence assessment was carried out using the GRADE methodology.
Results:
1. Effectiveness of cranberry products:
– In women with recurrent UTIs, cranberry products significantly reduced the risk of infection (RR 0.74; 95% CI 0.55-0.99).
– The effect was even stronger in children at risk of UTI (RR 0.46; 95% CI 0.32-0.68).
– People with an increased risk of infection after medical procedures also benefited from cranberries (RR 0.47; 95% CI 0.37-0.61).
– There were no significant benefits in older people (RR 0.93; 95% CI 0.67-1.30), pregnant women (RR 1.06; 95% CI 0.75-1.50) or patients with neurogenic bladder dysfunction (RR 0.97; 95% CI 0.78-1.19).
2. Comparison with antibiotics and probiotics:
– Cranberries were not significantly better or worse than antibiotics in two studies (RR 1.03; 95% CI 0.80-1.33).
– Compared to probiotics, cranberries showed stronger infection prevention in three studies (RR 0.39; 95% CI 0.27-0.56).
3. Product forms and dosage:
– Cranberry juice as well as capsules and tablets reduced the risk of infection.
– Differences between the dosage forms are not clearly understood, possibly due to variations in PAC content.
– The optimal PAC level is not standardized, although 36-72 mg/day is thought to be the most effective dose.
4. Side effects and adherence:
– The most common side effect was gastrointestinal discomfort (RR 1.33; 95% CI 1.00-1.77).
– Adherence was lower with cranberry juice than with tablets, presumably because of the sour taste.
Conclusion:
Cranberry products can reduce the risk of urinary tract infections, especially in women with recurrent UTIs, children and high-risk groups following medical procedures. The effect varies depending on the product form and dosage. For older people, pregnant women and people with neurogenic bladder dysfunction, the benefits are unclear. Future studies should investigate standardized PAC dosages and compare cranberries with established prevention strategies.