A Randomized, Double Blind, Controlled, Dose Dependent Clinical Trial to Evaluate the Efficacy of a Proanthocyanidin Standardized Whole Cranberry (Vaccinium macrocarpon) Powder on Infections of the Urinary Tract

Cranberries for preventing urinary tract infections

BACKGROUND

Cranberries contain proanthocyanidins (PACs), which inhibit the adherence of p-fimbriated Escherichia coli to the urothelial cells lining the bladder. Cranberry products have been used widely for several decades to prevent urinary tract infections (UTIs). This is the fifth update of a review first published in 1998 and updated in 2003, 2004, 2008, and 2012.

OBJECTIVES

To assess the effectiveness of cranberry products in preventing UTIs in susceptible populations.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register up to 13 March 2023 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

All randomised controlled trials (RCTs) or quasi-RCTs of cranberry products compared with placebo, no specific treatment or other intervention (antibiotics, probiotics) for the prevention of UTIs were included.

DATA COLLECTION AND ANALYSIS

At least two authors independently assessed and extracted data. Information was collected on methods, participants, interventions and outcomes (incidence of symptomatic UTIs, positive culture results, side effects, adherence to therapy). Risk ratios (RR) with 95% confidence intervals (CI) were calculated where appropriate. Study quality was assessed using the Cochrane risk of bias assessment tool. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

For this update, 26 new studies were added, bringing the total number of included studies to 50 (8857 randomised participants). The risk of bias for sequence generation and allocation concealment was low for 29 and 28 studies, respectively. Thirty-six studies were at low risk of performance bias, and 23 studies were at low risk of detection bias. Twenty-seven, 41, and 17 studies were at low risk of attrition bias, reporting bias and other bias, respectively. Forty-five studies compared cranberry products with placebo, water or no specific treatment in six different groups of participants. Twenty-six of these 45 studies could be meta-analysed for the outcome of symptomatic, culture-verified UTIs. In moderate certainty evidence, cranberry products reduced the risk of UTIs (6211 participants: RR 0.70, 95% CI 0.58 to 0.84; I² = 69%). When studies were divided into groups according to the treatment indication, cranberry products probably reduced the risk of symptomatic, culture-verified UTIs in women with recurrent UTIs (8 studies, 1555 participants: RR 0.74, 95% CI 0.55 to 0.99; I² = 54%), in children (5 studies, 504 participants: RR 0.46, 95% CI 0.32 to 0.68; I² = 21%) and in people with a susceptibility to UTIs due to an intervention (6 studies, 1434 participants: RR 0.47, 95% CI 0.37 to 0.61; I² = 0%). However, there may be little or no benefit in elderly institutionalised men and women (3 studies, 1489 participants: RR 0.93, 95% CI 0.67 to 1.30; I² = 9%; moderate certainty evidence), pregnant women (3 studies, 765 participants: RR 1.06, 95% CI 0.75 to 1.50; I² = 3%; moderate certainty evidence), or adults with neuromuscular bladder dysfunction with incomplete bladder emptying (3 studies, 464 participants: RR 0.97, 95% CI 0.78 to 1.19; I² = 0%; low certainty evidence). Other comparisons were cranberry products with probiotics (three studies) or antibiotics (six studies), cranberry tablets with cranberry liquid (one study), and different doses of PACs (two studies). Compared to antibiotics, cranberry products may make little or no difference to the risk of symptomatic, culture-verified UTIs (2 studies, 385 participants: RR 1.03, 95% CI 0.80 to 1.33; I² = 0%) or the risk of clinical symptoms without culture (2 studies, 336 participants: RR 1.30, 95% CI 0.79 to 2.14; I² = 68%). Compared to probiotics, cranberry products may reduce the risk of symptomatic, culture-verified UTIs (3 studies, 215 participants: RR 0.39, 95% CI 0.27 to 0.56; I = 0%). It is unclear whether efficacy differs between cranberry juice and tablets or between different doses of PACs, as the certainty of the evidence was very low. The number of participants with gastrointestinal side effects probably does not differ between those taking cranberry products and those receiving a placebo or no specific treatment (10 studies, 2166 participants: RR 1.33, 95% CI 1.00 to 1.77; I² = 0%; moderate certainty evidence). There was no clear relationship between compliance with therapy and the risk for repeat UTIs. No difference in the risk for UTIs could be demonstrated between low, moderate and high doses of PACs.

AUTHORS' CONCLUSIONS

This update adds a further 26 studies, taking the total number of studies to 50 with 8857 participants. These data support the use of cranberry products to reduce the risk of symptomatic, culture-verified UTIs in women with recurrent UTIs, in children, and in people susceptible to UTIs following interventions. The evidence currently available does not support its use in the elderly, patients with bladder emptying problems, or pregnant women.

Cranberry Supplements for Urinary Tract Infection Prophylaxis in Pregnant Women: A Systematic Review of Clinical Trials and Observational Studies on Efficacy, Acceptability, Outcomes Measurement Methods, and Studies' Feasibility

Cranberry supplements are commonly used to prevent urinary tract infections (UTIs). However, their usefulness is uncertain in pregnant women. We aimed to comprehensively summarize the current knowledge on cranberry supplements' efficacy and acceptability during pregnancy in addition to the outcomes measurement methods and studies' feasibility. To achieve it, we searched PubMed, PMC, and Europe PMC databases plus screened citations followed by critical appraisal of included eligible English-written primary studies that (1) focused on pregnant women supplemented with any cranberry supplements; (2) provided data on cranberry supplements' efficacy, acceptability, outcomes measurement methods, and studies' feasibility; (3) included human subjects; and (4) published worldwide. Two randomized clinical trials (RCTs) and one nested cohort study, including 1156 pregnant women in total, contributed to our analysis. A tendency toward UTI reduction was demonstrated, although the results' validity was impacted by significant juice-induced gastrointestinal intolerance (23%; 44 of 188 subjects). Changing the form of supplementation from cranberry juice to capsules reduced the issue, causing side effects in one of 49 subjects (2%). Nevertheless, both RCTs still experienced significant recruitment and retention problems, which were at 33% and 59% on average, respectively. Newly acquired safety data on 919 more subjects suggests no increased risks of all malformations, vaginal bleeding, and neonatal complications. Investigating cranberry capsules' efficacy as a non-antibacterial option for UTI prevention in pregnant women has become a feasible and important direction with the current advancement in understanding cranberry supplements' actions, recommended doses plus regimens, and their safety in the population. We reviewed the challenges and discovered knowledge gaps and the implementation strategies for future studies.

Cranberries for preventing urinary tract infections

BACKGROUND

Cranberries contain proanthocyanidins (PACs), which inhibit the adherence of p-fimbriated Escherichia coli to the urothelial cells lining the bladder. Cranberry products have been used widely for several decades to prevent urinary tract infections (UTIs). This is the fifth update of a review first published in 1998 and updated in 2003, 2004, 2008, and 2012.

OBJECTIVES

To assess the effectiveness of cranberry products in preventing UTIs in susceptible populations.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register up to 13 March 2023 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register Search Portal (ICTRP) and ClinicalTrials.gov.

SELECTION CRITERIA

All randomised controlled trials (RCTs) or quasi-RCTs of cranberry products compared with placebo, no specific treatment or other intervention (antibiotics, probiotics) for the prevention of UTIs were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed and extracted data. Information was collected on methods, participants, interventions and outcomes (incidence of symptomatic UTIs, positive culture results, side effects, adherence to therapy). Risk ratios (RR) with 95% confidence intervals (CI) were calculated where appropriate. Study quality was assessed using the Cochrane risk of bias assessment tool. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

For this update 26 new studies were added, bringing the total number of included studies to 50 (8857 randomised participants). The risk of bias for sequence generation and allocation concealment was low for 29 and 28 studies, respectively. Thirty-six studies were at low risk of performance bias, and 23 studies were at low risk of detection bias. Twenty-seven, 41, and 17 studies were at low risk of attrition bias, reporting bias and other bias, respectively. Forty-five studies compared cranberry products with placebo or no specific treatment in six different groups of participants. Twenty-six of these 45 studies could be meta-analysed for the outcome of symptomatic, culture-verified UTIs. In moderate certainty evidence, cranberry products reduced the risk of UTIs (6211 participants: RR 0.70, 95% CI 0.58 to 0.84; I² = 69%). When studies were divided into groups according to the treatment indication, cranberry products probably reduced the risk of symptomatic, culture-verified UTIs in women with recurrent UTIs (8 studies, 1555 participants: RR 0.74, 95% CI 0.55 to 0.99; I² = 54%), in children (5 studies, 504 participants: RR 0.46, 95% CI 0.32 to 0.68; I² = 21%) and in people with a susceptibility to UTIs due to an intervention (6 studies, 1434 participants: RR 0.47, 95% CI 0.37 to 0.61; I² = 0%). However, in low certainty evidence, there may be little or no benefit in elderly institutionalised men and women (3 studies, 1489 participants: RR 0.93, 95% CI 0.67 to 1.30; I² = 9%), pregnant women (3 studies, 765 participants: RR 1.06, 95% CI 0.75 to 1.50; I² = 3%), or adults with neuromuscular bladder dysfunction with incomplete bladder emptying (3 studies, 464 participants: RR 0.97, 95% CI 0.78 to 1.19; I² = 0%). Other comparisons were cranberry products with probiotics (three studies) or antibiotics (six studies), cranberry tablets with cranberry liquid (one study), and different doses of PACs (two studies). Compared to antibiotics, cranberry products may make little or no difference to the risk of symptomatic, culture-verified UTIs (2 studies, 385 participants: RR 1.03, 95% CI 0.80 to 1.33; I² = 0%) or the risk of clinical symptoms without culture (2 studies, 336 participants: RR 1.30, 95% CI 0.79 to 2.14; I² = 68%). Compared to probiotics, cranberry products may reduce the risk of symptomatic, culture-verified UTIs (3 studies, 215 participants: RR 0.39, 95% CI 0.27 to 0.56; I = 0%). It is unclear whether efficacy differs between cranberry juice and tablets or between different doses of PACs as the certainty of the evidence was very low. The number of participants with gastrointestinal side effects probably does not differ between those taking cranberry products and those receiving placebo or no specific treatment (10 studies, 2166 participants: RR 1.33, 95% CI 1.00 to 1.77; I² = 0%; moderate certainty evidence). There was no clear relationship between compliance with therapy and the risk for repeat UTIs. No difference in the risk for UTIs could be demonstrated between low, moderate and high doses of PACs.

AUTHORS' CONCLUSIONS

This update adds a further 26 studies taking the total number of studies to 50 with 8857 participants. These data support the use of cranberry products to reduce the risk of symptomatic, culture-verified UTIs in women with recurrent UTIs, in children, and in people susceptible to UTIs following interventions. The evidence currently available does not support its use in the elderly, patients with bladder emptying problems, or pregnant women.

Original Article Phytotherapy in Adults With Recurrent Uncomplicated Cystitis

BACKGROUND

Uncomplicated urinary tract infections are among the commonest bacterial infections. Because antibiotic resistance is on the rise, there is growing interest in alternative, non-antimicrobial treatment options. This systematic review presents the current evidence on phytotherapy for the treatment and prevention of recurrent uncomplicated cystitis.

METHODS

A systematic search of the relevant literature from January 2011 to August 2021 was carried out in the MEDLINE, Embase, and Cochrane Library databases and in two clinical trial registries. The trials included in the present review are ran - domized controlled trials (RCTs) of phytotherapeutic agents as monotherapy or combination therapy, in comparison to placebo, no treatment, non-pharmacological treatment, or drug treatment without any phytotherapeutic component. Two of the authors independently selected the publications, extracted the data, and estimated the risk of bias using the Cochrane Risk of Bias Tool.

RESULTS

12 RCTs with a total of 1797 female patients were included. A trial of acute therapy with Chinese plant-based medicine revealed non-inferiority to antibiotic treatment. Six trials of prophylaxis with cranberry products yielded mixed results with regard to efficacy against recurrent urinary tract infections. A trial of Seidlitzia rosmarinus for the prevention of cystitis showed that its use was associated with a lower cystitis rate than placebo (at 6 months: 33 vs. 73%, p <0.001). In all trials but one, the risk of bias was unclear or high. No standardized assessment of adverse events was carried out.

CONCLUSION

Phytotherapeutic agents are an option for the treatment and prevention of recurrent cystitis in women. Given the heterogeneous state of the evidence on phytotherapy, no dependable recommendations can now be made for the clinical management of these patients with respect to phytotherapeutic agents.

Consumption of cranberry as adjuvant therapy for urinary tract infections in susceptible populations: A systematic review and meta-analysis with trial sequential analysis

The efficacy of cranberry (Vaccinium spp.) as adjuvant therapy in preventing urinary tract infections (UTIs) remains controversial. This study aims to update and determine cranberry effects as adjuvant therapy on the recurrence rate of UTIs in susceptible groups. According to PRISMA guidelines, we conducted a literature search in Web of Science, PubMed, Embase, Scopus, and the Cochrane Library from their inception dates to June 2021. We included articles with data on the incidence of UTIs in susceptible populations using cranberry-containing products. We then conducted a trial sequential analysis to control the risk of type I and type II errors. This meta-analysis included 23 trials with 3979 participants. We found that cranberry-based products intake can significantly reduce the incidence of UTIs in susceptible populations (risk ratio (RR) = 0.70; 95% confidence interval(CI): 0.59 ~ 0.83; P<0.01). We identified a relative risk reduction of 32%, 45% and 51% in women with recurrent UTIs (RR = 0.68; 95% CI: 0.56 ~ 0.81), children (RR = 0.55; 95% CI: 0.31 ~ 0.97) and patients using indwelling catheters (RR = 0.49; 95% CI: 0.33 ~ 0.73). Meanwhile, a relative risk reduction of 35% in people who use cranberry juice compared with those who use cranberry capsule or tablet was observed in the subgroup analysis (RR = 0.65; 95% CI: 0.54 ~ 0.77). The TSA result for the effects of cranberry intake and the decreased risk of UTIs in susceptible groups indicated that the effects were conclusive. In conclusion, our meta-analysis demonstrates that cranberry supplementation significantly reduced the risk of developing UTIs in susceptible populations. Cranberry can be considered as adjuvant therapy for preventing UTIs in susceptible populations. However, given the limitations of the included studies in this meta-analysis, the conclusion should be interpreted with caution.

Safety of Cranberry: Evaluation of Evidence of Kidney Stone Formation and Botanical Drug-Interactions

Cranberry is a popular ingredient in dietary supplements in the U. S. and is commonly used for preventing urinary tract infections. Because of its popularity in dietary supplements, the U. S. Pharmacopeial Convention has developed quality standards for cranberry ingredients. The purpose of this review was to determine if there are safety issues that should preclude the admission of cranberry ingredients from the development of U. S. Pharmacopeial Convention quality standards. Based on the totality of the data, the U. S. Pharmacopeial Convention concluded that cranberry ingredients are not known to be associated with serious risks to human health when consumed properly in dietary supplements and therefore were admitted for standard development. Although published clinical and animal data indicated that cranberry is not associated with serious adverse effects, interactions with warfarin and kidney stone formation were identified as potential risks. Studies have reported contradictory data regarding the role of cranberry in kidney stone formation, with some reports suggesting cranberry is associated with a reduced risk of kidney stones. Interactions with warfarin were not associated with moderate intakes of cranberry juice (240 - 480 mL). Some reports suggested that the potential for warfarin interactions requires excessive intakes of cranberry juice (1 - 2 L/day) or cranberry extracts (3000 mg/day). Cases of warfarin interactions with cranberry have mostly involved patients with serious illnesses and/or individuals taking concomitant medications. Based on these findings, the U. S. Pharmacopeial Convention concluded that the use of cautionary labeling statements regarding interactions with warfarin or kidney stone formation is not necessary in the development of quality standards for cranberry ingredients.

Exploring CNS effects of American traditional medicines using zebrafish models

Although American traditional medicine (ATM) has been practiced for millennia, its complex multi-target mechanisms of therapeutic action remain poorly understood. Animal models are widely used to elucidate the therapeutic effects of various ATMs, including their modulation of brain and behavior. Complementing rodent models, the zebrafish (Danio rerio) is a promising novel organism in translational neuroscience and neuropharmacology research. Here, we emphasize the growing value of zebrafish for testing neurotropic effects of ATMs and outline future directions of research in this field. We also demonstrate the developing utility of zebrafish as complementary models for probing CNS mechanisms of ATM action and their potential to treat brain disorders.

Cranberry Extract for Symptoms of Acute, Uncomplicated Urinary Tract Infection: A Systematic Review

BACKGROUND

Effective alternatives to antibiotics for alleviating symptoms of acute infections may be appealing to patients and enhance antimicrobial stewardship. Cranberry-based products are already in wide use for symptoms of acute urinary tract infection (UTI). The aim of this review was to identify and critically appraise the supporting evidence.

METHODS

The protocol was registered on PROSPERO. Searches were conducted of Medline, Embase, Amed, Cinahl, The Cochrane library, Clinicaltrials.gov and WHO International Clinical Trials Registry Platform. We included randomised clinical trials (RCTs) and non-randomised studies evaluating the effect of cranberry extract in the management of acute, uncomplicated UTI on symptoms, antibiotic use, microbiological assessment, biochemical assessment and adverse events. Study risk of bias assessments were made using Cochrane criteria.

RESULTS

We included three RCTs (n = 688) judged to be at moderate risk of bias. One RCT (n = 309) found that advice to consume cranberry juice had no statistically significant effect on UTI frequency symptoms (mean difference (MD) -0.01 (95% CI: -0.37 to 0.34), p = 0.94)), on UTI symptoms of feeling unwell (MD 0.02 (95% CI: -0.36 to 0.39), p = 0.93)) or on antibiotic use (odds ratio 1.27 (95% CI: 0.47 to 3.43), p = 0.64), when compared with promoting drinking water. One RCT (n = 319) found no symptomatic benefit from combining cranberry juice with immediate antibiotics for an acute UTI, compared with placebo juice combined with immediate antibiotics. In one RCT (n = 60), consumption of cranberry extract capsules was associated with a within-group improvement in urinary symptoms and Escherichia coli load at day 10 compared with baseline (p < 0.01), which was not found in untreated controls (p = 0.72). Two RCTs were under-powered to detect differences between groups for outcomes of interest. There were no serious adverse effects associated with cranberry consumption.

CONCLUSION

The current evidence base for or against the use of cranberry extract in the management of acute, uncomplicated UTIs is inadequate; rigorous trials are needed.

Cranberry Reduces the Risk of Urinary Tract Infection Recurrence in Otherwise Healthy Women: A Systematic Review and Meta-Analysis

Background: Cranberry (Vaccinium spp.) has been advocated for treatment of urinary tract infection (UTI); however, its efficacy is controversial. Women have a 50% risk of UTI over their lifetime, and ∼20-30% experience a subsequent UTI recurrence.Objective: We conducted this meta-analysis to assess the effect of cranberry on the risk of UTI recurrence in otherwise healthy women.Methods: Literature published before January 2011 was obtained from 2 published systematic reviews, and we conducted updated searches in EMBASE and MEDLINE (through July 2017). We included randomized controlled trials that were conducted in generally healthy nonpregnant women aged ≥18 y with a history of UTI, compared cranberry intervention to a placebo or control, and reported the outcome as the number of participants experiencing a UTI. Two researchers conducted abstract and full-text screenings, data extractions, and risk of bias assessments independently, and discrepancies were resolved by group consensus. Meta-analyses were performed by using Stata SE software (version 13). We employed a fixed-effect model using the Mantel-Haenszel method to estimate the summary risk if the heterogeneity was low to moderate (I² < 50%). Otherwise, we applied a random-effects model using the DerSimonian-Laird method.Results: We identified 7 randomized controlled trials conducted in healthy women at risk of UTI (n = 1498 participants). Results of the meta-analysis showed that cranberry reduced the risk of UTI by 26% (pooled risk ratio: 0.74; 95% CI: 0.55, 0.98; I² = 54%). Risk of bias indicated that 2 studies had high loss to follow-up or selective outcome reporting. Overall, the studies were relatively small, with only 2 having >300 participants.Conclusion: These results suggest that cranberry may be effective in preventing UTI recurrence in generally healthy women; however, larger high-quality studies are needed to confirm these findings. This trial was registered at crd.york.ac.uk/prospero as CRD42015024439.

Identification and Characterization of Glycopeptides from Egg Protein Ovomucin with Anti-Agglutinating Activity against Porcine K88 Enterotoxigenic Escherichia coli Strains

Ovomucin is a glycoprotein from egg white with potential to act as an anti-adhesive agent against infectious diseases. This study aimed to determine whether ovomucin or ovomucin hydrolysates could prevent adhesion of two porcine K88 enterotoxigenic Escherichia coli (ETEC) strains. Adhesion was assessed in vitro using a hemagglutination assay. Ovomucin hydrolysates, but not intact ovomucin, prevented adhesion of ETEC to porcine erythrocytes. The ovomucin hydrolysate prepared by acid protease II exhibited the best anti-agglutinating activity against both strains; this hydrolysate was fractionated by cation exchange chromatography and reverse-phase high-performance liquid chromatography (HPLC). The most active fractions, F3(9) and F7(1), with minimal inhibitory concentrations of 0.03 and 0.25 g/L against strains ECL13795 and ECL13998, respectively, were subjected to structural characterization. Six identified glycopeptides were all derived from α-ovomucin, composed of a pentasaccharide core of two N-acetylglucosamine and three mannose residues (GlcNAc₂Man₃) and a bisecting N-acetylglucosamine (GlcNAc). The terminal β-linked galactose from these glycopeptides could be one of the binding sites for K88_ac fimbriae.

Cranberries and Urinary Tract Infections: How Can the Same Evidence Lead to Conflicting Advice?

Cranberry has been used traditionally to prevent urinary tract infections (UTIs), primarily among generally healthy women prone to recurrent UTIs. Results from a number of published clinical studies have supported this benefit; however, meta-analyses on cranberry and UTI prevention have reported conflicting conclusions. This article explores the methodological differences that contributed to these disparate findings. Despite similar research questions, the meta-analyses varied in the studies that were included, as well as the data that were extracted. In the 2 most comprehensive systematic reviews, heterogeneity was handled differently, leading to an I(2) of 65% in one and 43% in the other. Most notably, the populations influencing the conclusions varied. In one analysis, populations with pathological/physiological conditions contributed 75.6% of the total weight to the summary risk estimate (RR: 0.86; 95% CI: 0.71, 1.04); another weighted the evidence relatively equally across UTI populations (RR: 0.62; 95% CI: 0.49, 0.80); and a third included only women with recurrent UTIs (RR: 0.53; 95% CI: 0.33, 0.83). Because women with recurrent UTIs are the group to whom most recommendations regarding cranberry consumption is directed, inclusion of other groups in the efficacy assessment could influence clinical practice quality. Therefore, conclusions on cranberry and UTIs should consider differences in results across various populations studied when interpreting results from meta-analyses.

Non-Antibiotic Prophylaxis for Urinary Tract Infections

Increasing antimicrobial resistance has stimulated interest in non-antibiotic prophylaxis of recurrent urinary tract infections (UTIs). Well-known steps in the pathogenesis of UTIs are urogenital colonization and adherence of uropathogens to uroepithelial cell receptors. To prevent colonization in postmenopausal women, vaginal, but not oral, estrogens have been shown to restore the vagina lactobacilli flora, reduce vaginal colonization with Enterobacteriaceae, and reduce the number of UTIs compared to placebo. Different lactobacilli strains show different results in the prevention of recurrent UTIs. Intravaginal suppositories with Lactobacillus crispatus in premenopausal women and oral capsules with Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 in postmenopausal women are promising. Ascorbic acid (vitamin C) cannot be recommended for the prevention of UTIs. Cranberries are thought to contain proanthocyanidins that can inhibit adherence of P-fimbriated E. coli to the uroepithelial cell receptors. Cranberry products decreased UTI recurrences about 30%-40% in premenopausal women with recurrent UTIs, but are less effective than low-dose antimicrobial prophylaxis. However, the optimal dose of cranberry product has still to be determined. Initially OM-89, a vaccine with 18 heat-killed E. coli extracts, seemed promising, but this was not confirmed in a recently randomized trial.

Are High Proanthocyanidins Key to Cranberry Efficacy in the Prevention of Recurrent Urinary Tract Infection?

Most research on American cranberry in the prevention of urinary tract infection (UTI) has used juices. The spectrum of components in juice is limited. This study tested whether whole cranberry fruit powder (proanthocyanidin content 0.56%) could prevent recurrent UTI in 182 women with two or more UTI episodes in the last year. Participants were randomized to a cranberry (n = 89) or a placebo group (n = 93) and received daily 500 mg of cranberry for 6 months. The number of UTI diagnoses was counted. The intent-to-treat analyses showed that in the cranberry group, the UTIs were significantly fewer [10.8% vs. 25.8%, p = 0.04, with an age-standardized 12-month UTI history (p = 0.01)]. The Kaplan-Meier survival curves showed that the cranberry group experienced a longer time to first UTI than the placebo group (p = 0.04). Biochemical parameters were normal, and there was no significant difference in urinary phenolics between the groups at baseline or on day180. The results show that cranberry fruit powder (peel, seeds, pulp) may reduce the risk of symptomatic UTI in women with a history of recurrent UTIs.

Cranberries for preventing urinary tract infections

BACKGROUND

Cranberries have been used widely for several decades for the prevention and treatment of urinary tract infections (UTIs). This is the third update of our review first published in 1998 and updated in 2004 and 2008.

OBJECTIVES

To assess the effectiveness of cranberry products in preventing UTIs in susceptible populations.

SEARCH METHODS

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL in The Cochrane Library) and the Internet. We contacted companies involved with the promotion and distribution of cranberry preparations and checked reference lists of review articles and relevant studies.Date of search: July 2012

SELECTION CRITERIA

All randomised controlled trials (RCTs) or quasi-RCTs of cranberry products for the prevention of UTIs.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed and extracted data. Information was collected on methods, participants, interventions and outcomes (incidence of symptomatic UTIs, positive culture results, side effects, adherence to therapy). Risk ratios (RR) were calculated where appropriate, otherwise a narrative synthesis was undertaken. Quality was assessed using the Cochrane risk of bias assessment tool.

MAIN RESULTS

This updated review includes a total of 24 studies (six cross-over studies, 11 parallel group studies with two arms; five with three arms, and two studies with a factorial design) with a total of 4473 participants. Ten studies were included in the 2008 update, and 14 studies have been added to this update. Thirteen studies (2380 participants) evaluated only cranberry juice/concentrate; nine studies (1032 participants) evaluated only cranberry tablets/capsules; one study compared cranberry juice and tablets; and one study compared cranberry capsules and tablets. The comparison/control arms were placebo, no treatment, water, methenamine hippurate, antibiotics, or lactobacillus. Eleven studies were not included in the meta-analyses because either the design was a cross-over study and data were not reported separately for the first phase, or there was a lack of relevant data. Data included in the meta-analyses showed that, compared with placebo, water or not treatment, cranberry products did not significantly reduce the occurrence of symptomatic UTI overall (RR 0.86, 95% CI 0.71 to 1.04) or for any the subgroups: women with recurrent UTIs (RR 0.74, 95% CI 0.42 to 1.31); older people (RR 0.75, 95% CI 0.39 to 1.44); pregnant women (RR 1.04, 95% CI 0.97 to 1.17); children with recurrent UTI (RR 0.48, 95% CI 0.19 to 1.22); cancer patients (RR 1.15 95% CI 0.75 to 1.77); or people with neuropathic bladder or spinal injury (RR 0.95, 95% CI: 0.75 to 1.20). Overall heterogeneity was moderate (I² = 55%). The effectiveness of cranberry was not significantly different to antibiotics for women (RR 1.31, 95% CI 0.85, 2.02) and children (RR 0.69 95% CI 0.32 to 1.51). There was no significant difference between gastrointestinal adverse effects from cranberry product compared to those of placebo/no treatment (RR 0.83, 95% CI 0.31 to 2.27). Many studies reported low compliance and high withdrawal/dropout problems which they attributed to palatability/acceptability of the products, primarily the cranberry juice. Most studies of other cranberry products (tablets and capsules) did not report how much of the 'active' ingredient the product contained, and therefore the products may not have had enough potency to be effective.

AUTHORS' CONCLUSIONS

Prior to the current update it appeared there was some evidence that cranberry juice may decrease the number of symptomatic UTIs over a 12 month period, particularly for women with recurrent UTIs. The addition of 14 further studies suggests that cranberry juice is less effective than previously indicated. Although some of small studies demonstrated a small benefit for women with recurrent UTIs, there were no statistically significant differences when the results of a much larger study were included. Cranberry products were not significantly different to antibiotics for preventing UTIs in three small studies. Given the large number of dropouts/withdrawals from studies (mainly attributed to the acceptability of consuming cranberry products particularly juice, over long periods), and the evidence that the benefit for preventing UTI is small, cranberry juice cannot currently be recommended for the prevention of UTIs. Other preparations (such as powders) need to be quantified using standardised methods to ensure the potency, and contain enough of the 'active' ingredient, before being evaluated in clinical studies or recommended for use.