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Cranberry, vaccinium macrocarpon, is a plant commonly grown in North America that is harvested for its berries. It has been reported that Native Americans were the first group to use cranberries for food, fabric dye and as a healing agent.
Cranberry was first used traditionally by Native Americans as a treatment for bladder and kidney ailments. In addition to traditional usage, cranberry has a long history of scientific research studying its benefit on the urinary tract.
Bacteria species such as Escherischia coli (E. coli), Streptococcus, Enterobacteria, Klebsiella and Proteus can inhabit the urinary tract, grow and multiply and essentially cause infections. Since urine is usually sterile, pathogenic microorganisms must enter through the urethra and adhere to the host tissue. Cranberry supports the health of the urinary tract by inhibiting the adhesion of E. coli to the epithelial cell lining of the urethra. One of the primary beneficial compounds in cranberry, proanthocyandins (PACs) help protect against bacteria by collecting in the urine relatively intact and also by binding to pathogenic bacteria from the colon and decreasing their harmfulness (1).
In a randomized, double-blind, placebo controlled, cross-over trial of healthy women, Tempera et al. found that individuals taking a supplement containing 120 mg cranberry extract including 36 mg PACs experienced an approximately 50.9% reduction in bacterial adhesiveness over the course of one week (2).
Results from a 90-day randomized, placebo-controlled trial found that women given 500 mg cranberry extract standardized to 1.5% PACs reduced urinary E. coli adherence by 36%. Women given 1000 mg daily showed even further reduction of E. coli at 65% (3).
Another placebo controlled human trial analyzed the urine of 32 women consuming 0, 18, 36, or 72 mg PAC equivalents/day in cranberry powder capsules and found that there was a significant dose-dependent reduction in the bacterial adherence to human epithelial cells 24 hours after ingestion compared to placebo (4).
A 2007 double-blind, randomized, crossover trial of eight women evaluated the ability of a cranberry supplement on preventing bacteria from adhering to the human uroepithelial cells. Researchers found that 12 hours after consuming 108 mg of cranberry in capsule form, there was a significant decrease in bacterial adherence to human uroepithelial cells compared with placebo (5).
Health Canada reviewed information supporting the safety, efficacy or quality of cranberry and determined the following claims to be acceptable for cranberry natural health products. The doses required to bear these claims are preparations equivalent to 90-950 ml fruit juice, per day or preparations equivalent to 10-30 g fresh fruit, per day (6).
• (Traditionally) used in Herbal Medicine to help prevent (recurrent) urinary tract infections (UTIs)
• (Used in Herbal Medicine to) help(s) prevent recurrent urinary tract infections (UTIs) in women
Monograph of Vaccinium macrocarpon
Shaheen G, Ahmad I, Mehmood A, Akhter N et al., n. Journal of Medicinal Plants Research. 2011. October. Vol. 5(22). 5340-46. , 2011
Inhibitory activity of cranberry extract on the bacterial adhesiveness in the urine of women: an ex-vivo study.
Tempera G, Corsello S, Genovese C, Caruso F, IJIP, 2010
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
Sengupta K, Alluri K, GolakotiT, Gottumukkala G, Raavi J et al. , Current Bioactive Compounds, 2017
Dosage effect on uropathogenic Escherichia coli anti-adhesion activity in urine following consumption of cranberry powder standardized for proanthocyanidin content: a multicentric randomized double blind study
Howell A, Botto H, Combescure C, Blanc-Potard A, Guasa L et al. , BMC Infectious Diseases, 2010
In-vitro and in-vivo evidence of dose-dependent decrease of uropathogenic Escherichia coli virulence after consumption of commercial Vaccinium macrocarpon (cranberry) capsules
Lavigne JP, Bourg G, Combescure C, Botto H, Sotto A. , Clin Microbiol Infect, 2008
Natural Health Product Monograph: Cranberry
Health Canada, Health Canada, 2011