Objective
In the United States, urinary tract infections are one of the most common bacterial infections, affecting 8 million people per year.
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Approximately 50% of women will develop a urinary tract infection during their lifetime.1
In 2000, the United States spent $2.14 billion toward UTI treatment.1
Urinary tract infections are generally considered easily treatable, with the majority of patients prescribed a regimen of antibiotics. Overuse of antibiotic therapy has burdened the clinical management of urinary tract infections, which has led to the increasing prevalence of antibiotic resistance.1
An alternative prophylactic is needed to combat the emergence of ineffective treatments. Cranberry may be beneficial in preventing recurrent urinary tract infections in certain at-risk populations.2
The mechanism of action of cranberry was initially thought to be due to the fruit’s acidity, producing a bacteriostatic effect in the urine.
2
More recently it was found that components in cranberry called proanthocyanidins, condensed tannin molecules with A-type linkages, exhibit potent bacterial antiadhesion activity.3
Herbals, such as cranberry, are not required to undergo the same rigorous testing to establish efficacy, dosage and safety as pharmaceutical agents regulated by the Food and Drug Administration.4
We sought to measure the bacterial anti-adhesion activity and proanthocyanidin levels in 7 commercially available cranberry supplements.Study Design
The bioactivity of the 7 cranberry supplements in preventing adhesion of uropathogenic P-fimbriated Escherichia coli was tested by measuring the ability of the supplements to suppress agglutination of human red blood cells (A1, Rh+) following incubation with the bacteria.
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Endpoint concentrations were compared among the cranberry products, with the lowest concentration representing the highest bacterial antiadhesion activity. Wells containing bacteria plus phosphate-buffered saline, human red blood cells plus phosphate-buffered saline, bacteria plus test fraction, and human red blood cells plus test fraction served as negative controls for agglutination, and wells containing bacteria plus human red blood cells served as a positive control for agglutination.Results
Antiadhesion activity of the supplements ranged from 0.47 to 60 mg/mL, with 4 products yielding negative results (Table). Typically, cranberry products that result in production of antiadhesion activity in urine when consumed have whole-product activities of 0.47–7.5 mg/mL. Proanthocyanidin levels ranged from 0.56 to 175 mg/g. In clinical trials, consumption of cranberry products containing about 36 mg of proanthocyanidin have resulted in significant reductions in recurrent urinary tract infections.
TableComparison of cranberry products with PAC level, antiadhesion activity of the whole product, and antiadhesion of the isolated PACs
| Product | PAC level, mg/g | Antiadhesion (MIC) whole product, mg/mL | Antiadhesion (MIC) of PACs, μg/mL |
|---|---|---|---|
| 1 | 25.4 | 3.5-7.5 | 156 |
| 2 | 4 | Negative | 5000 |
| 3 | 4 | 0.60 | 312 |
| 4 | 175 | 0.47 | 78 |
| 5 | 1.2 | Negative | 2496 |
| 6 | 1.4 | Negative | 2496 |
| 7 | 0.56 | Negative | 312–624 |
MIC, minimal inhibitory concentrations; PAC, proanthocyanidin.
Chughtai. Commercial cranberry dietary supplements. Am J Obstet Gynecol 2016.
Conclusion
Despite clinical trials showing the efficacy of cranberry in preventing urinary tract infections, the actual antiadhesion activity and concentration of active proanthocyanidins in commercially available supplements is highly variable. In this study, several products contained virtually no active cranberry compounds. The clinical significance of this suggests that, although some are very potent, not all cranberry supplements have sufficient active compound to potentially achieve biologically relevant outcomes for urinary tract infection prevention. Although the benefits of utilizing cranberry for the maintenance of urinary tract health are definitely warranted because of resistance issues associated with antibiotic use, both physicians and patients alike need to be aware of the variability in quality of supplements available to consumers. Additionally, there needs to be stricter guidelines on the labeling and claims of these herbal medications.
References
- Urinary tract infections: current and emerging management strategies.Clin Infect Dis. 2013; 57: 719-724
- Cranberry capsules (2 taken twice daily for an average 38 days) reduce the risk of postoperative urinary tract infection in women undergoing benign gynaecological surgery involving intraoperative catheterisation.Evid Based Med. 2015; 20: 137
- Comprehensive assessment of the quality of commercial cranberry products. Phenolic characterization and in vitro bioactivity.J Agric Food Chem. 2012; 60: 3396-3408
- Analytical accuracy and reliability of commonly used nutritional supplements in prostate disease.J Urol. 2002; 168 (discussion 154): 150-154
- A-type proanthocyanidin trimers from cranberry that inhibit adherence of uropathogenic P-fimbriated Escherichia coli.J Nat Prod. 2000; 63: 1225-1228
Article info
Publication history
Published online: April 05, 2016
Footnotes
The authors report no conflict of interest.
Identification
Copyright
© 2016 Elsevier Inc. All rights reserved.
