Cranberry juice and urinary tract infections: what is the evidence?

Abstract

I is well “known” by the general lay public that cranberry juice is helpful in treating and preventing urinary tract infections (UTIs). However, the evidence for this assumption has never been critically reviewed in urologic reports or elsewhere. The evidence for the two proposed mechanisms of action of cranberry juice, urinary acidification and inhibition of bacterial adherence, are critically analyzed. Blatherwick1 in 1914 reported that cranberries are rich in benzoic acid and that benzoic acid is excreted as hippuric acid in the urine. For years, it was reported that the beneficial effect of cranberry juice was through the acidification of urine.2–4 We review the more current studies on the mechanism of action of cranberry juice on UTIs and its possible utility in the treatment of UTIs. Cranberries are one of three major native North American fruits, the others being concord grapes and blueberries. Native American Indians used the berries as a food source. In addition, they believed cranberries had medicinal properties. From the 1600s to the 1800s, cranberries were reportedly used for a variety of complaints, including blood disorders, stomach ailments, liver problems, and fevers. In the 1800s, cranberries were used by seamen to prevent scurvy at sea. Cranberries or Vaccinium macrocarpon are mainly grown in Massachusetts, Wisconsin, New Jersey, Oregon, Washington, and Canada. Cranberries can be processed into fresh fruit, concentrate, sauce products, and juice drinks. The single strength juice is very acidic (pH 5 2.5 or less) and is unpalatable. In the early 1950s, the cranberry juice cocktail was developed. Cranberry juice cocktail is a mixture of single strength cranberry juice (at least 25% by volume), sweetener, water, and vitamin C. Table I shows the composition of raw cranberries and cranberry juice per 100 g.5