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What's the use of cranberry juice?

About one quarter of women will experience a urinary tract infection during their life. Especially elderly women are at high risk. Escherichia coli is the main bacteria responsible for urinary tract infections. Antibiotics are mostly used to treat urinary tract infections but they have often side effects such as Candida infection or diarrhoea. Consumption of cranberry juice is a well established traditional method to prevent and cure urinary tract infections. The aim of this study was to investigate the efficacy of cranberry juice as a therapy. For this purpose scientific literature published between 1966 and 1999 was studied.

Cranberry is native to North America. The juice of the cranberry is very acid and astringent. In order to make cranberry juice more palatable it is diluted with water and sweetened with sugar. Mainly this diluted drink or a mix with other juices is available in the shops. Cranberry juice has been tested for its use to prevent blocking of urinary catheters, to deodorize urine and to heal skin around stomas, and for its properties as anticarcinogen, antifungal and antioxidant. Most research has been done on the prevention and treatment of urinary tract infections. First is was believed that cranberry acted by acidifying urine or by the bacteriostatic activity of hippuric acid. Later is was discovered that cranberry juice acted by reducing the adherence of bacteria to the epithelial cells of membranes. Cranberry juice is more effective in preventing bacteria for adhering to epithelial cells than removing bacteria already attached to cell membranes. Therefore, cranberry juice is more effective in preventing than treating urinary tract infections. One study published in 1997 by Dignam R and colleagues in the Journal of the American Geriatrics Society and entitled 'The Effect of Cranberry Juice on Urinary Tract Infection Rates in a Long Term Care Facility' showed that the consumption of cranberry juice of cranberry capsules reduced the rate of urinary tract infections from 27 to 20 per month. Many other studies, many of which are uncontrolled or anecdotal, show a favourable effect of cranberry juice.

Other uncontrolled studies have shown that cranberry juice reduces urinary odour and burning sensation, reduces damage of skin around stomas and reduces urinary calcium excretion.

In vitro studies have suggested that cranberry juice may have other non-urinary health benefits. The following health benefits have been suggested: anti-carcinogenic, fungistatic, inhibition of low density lipoprotein oxidation and prevention of formation of dental plaques.

It is still unknown if bacteria develop resistance against cranberry juice. The optimal dose of cranberry juice or cranberry extracts is still unknown. A possible disadvantage in the use of cranberry juice is its high oxalate content, which may increase the risk of kidney stone formation. Another disadvantage of cranberry juice is its high cost, especially if one would use cranberry juice daily for preventive purposes.

Source: Harkins KJ. What's the use of cranberry juice?. Age Ageing. 2000 January;29(1):9-12

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