Cranberries come form shrubs that grow in swamps either in North America or Europe. Cranberries became famous in American cuisine following the 1621 meal of Thanksgiving by the Pilgrims. Native Americans ate the berries for various complaints, including the relief of ‘bad fever’, to cleanse the stomach, relieve nausea, and treating bladder complaints. In the 1840’s, German chemists found that cranberry consumption could produce urine containing hippuric acid. At about 1900, in the U.S. it was discovered that the continual consumption of cranberries could prevent UTIs. Since that time, women have used cranberries for this purpose. Everybody seems to know of the use of cranberry juice for urinary tract infections, yet clinical evidence has been catching up to its reputation (McKenna et al., 2002).
Originally, it was thought that cranberry juice only worked by producing acidic urine. However, after there were doubts of this mechanism, it was found that cranberries prevent E. coli from adhering to the lining of the urinary tract. Cranberries are available in many forms, including juice (sweetened and non-sweetened), fresh berries, dehydrated fruit juice concentrate in capsules, berry tea, and extracts. It is important that the form of cranberry is not too diluted (as is the case of many commercial ‘cranberry’ juice) for efficacy (McKenna et al., 2002).
The reviews by Jepson et al. (2000, 2001, and 2004) are telling in that early on, little clinical evidence could be found to confirm cranberry’s efficacy. However, since the year 2000 clinical trials are becoming higher quality.
Urinary Tract Infection
In a review of the clinical studies on the effectiveness of cranberry products for urinary tract infections (UTIs), Raz et al. (2004) found that approximately a dozen trials had been performed, but the trials suffered a number of limitations. One of the limitations was stated as the use of a wide variety of cranberry products, such as cranberry juice concentrate, cranberry juice cocktail, and cranberry capsules with different dosing regimens.
In a systematic review of cranberries (especially cranberry juice) on urinary tract infections (UTIs) data was collected consisting of randomized, or semi-randomized, controlled trials of cranberry juice/products. Seven trials met the criteria, and in 6 trials, the effectiveness of cranberry juice vs. water or placebo was tested, and in 2 trials the effectiveness of cranberry tablets vs. placebo was tested. Two of the well-designed randomized clinical trials provided evidence for the efficacy of cranberry juice (with significant results) over 12 months of use in women. However, it was unclear whether cranberry juice was efficacious in the other groups, and what the optimum dosage or method of administration (Jepson et al., 2004). In an earlier review with the same inclusion criteria, only 5 trials were found to meet the criteria. The reviewers concluded the trials available at that time were of small size, and too poor of quality to interpret reliable results (Jepson et al., 2001). Just one year earlier, in a similar systematic review, no trials were found to fit the inclusion criteria (Jepson, 2000).
A randomized, double-blind, placebo-controlled trial was conduced in order to determine whether antibacterial effects of cranberry juice are effective in reducing or eliminating bacteriuria and pyuria in people with spinal cord injury (SCI). Each participant was administered 2 g of concentrated cranberry juice or placebo in capsule for 6 months. Cranberry extract was not found to produce significant differences in urinary bacterial colonies from control (Waites et al., 2004).
In a randomized, placebo-controlled trial cranberry tablets (concentrated juice) were compared to cranberry juice and placebo for efficacy and cost effectiveness. The participants (women) were divided into three groups, placebo juice + placebo tablets versus placebo juice + cranberry tablets, versus cranberry juice + placebo tablets. Tablets were administered two times daily, and the juice 250 ml three times daily. Cost effectiveness was calculated as dollar cost per urinary tract infection. Both cranberry juice and tablets were found to significantly reduce the number of patients experiencing at least 1 symptomatic UTI/year. The cost of prophylaxis was $624 for cranberry tablets and $1400 for cranberry juice. Cost effectiveness ratios found cranberry tablets to be two times more cost effective than the juice for UTIs (Stothers, 2002).
Habash et al. (1999) conducted a study on the comparison of water consumption, ascorbic acid or cranberry supplements on urine acidity and other measures. Ascorbic acid was the only treatment to consistently produce acidic urine. Urine collected after cranberry or ascorbic acid both had lower initial deposition rates and numbers of Escherichia coli and Enterococcus faecalis, but not other antimicrobials; whereas, water increased deposition rates and number of E. coli and E. faecalis.
In a randomized, double-blind, placebo-controlled trial of cranberry juice on bacteriuria and pyuria in elderly women, 153 elderly women were administered either cranberry juice (300 mL daily) or placebo. The cranberry juice reduced the frequency of bacteriuria with pyuria in older women (Avorn et al., 1994).
Pedersen et al. (2000) conducted a placebo controlled comparison of blueberry juice to cranberry juice for increasing plasma phenolic content and antioxidant activity. The participants were given either 500 ml of blueberry juice, cranberry juice, or a sucrose solution. Blood and urine samples were collected and analyzed after consuming the juice. Cranberry juice, but not blueberry juice, produced an increase in the plasma antioxidant capacity, that may be explained by an increase in vitamin C that was absent in blueberry juice.
Safety / Dosage
A typical daily dosage that has been recommended for cranberry, is 1/2 cup for the fresh fruit, 15 mL of the dried fruit, 90 ml of the juice cocktail (1/3 of which is pure juice). For an active UTI, the dosage is increased to between 12-32 fl oz, or 390-960 mL. Some products may available on the market that are standardized to total organic acids or polyphenolic content (McKenna et al., 2002).
Cranberry juice, when taken at the recommended levels, has no known side effects. In people with tendency to developing kidney stones, the limitation of cranberry juice intake is recommended to no more than one liter per day (McKenna et al., 2002).
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8.Raz R, Chazan B, Dan M. Cranberry juice and urinary tract infection.
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10.Stothers L. A randomized trial to evaluate effectiveness and cost effectiveness of naturopathic cranberry products as prophylaxis against urinary tract infection in women. Can J Urol. 2002 Jun;9(3):1558-62.
11.Waites KB, Canupp KC, Armstrong S, DeVivo MJ. Effect of cranberry extract on bacteriuria and pyuria in persons with neurogenic bladder secondary to spinal cord injury. J Spinal Cord Med. 2004;27(1):35-40.
EDITOR'S NOTE: This monograph can be found in The Health Professional's Guide to Dietary Supplements (Lippincott, Williams & Wilkins) by Shawn M. Talbott, PhD and Kerry Hughes, MS.