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Cranberry (Vaccinium macrocarpon)

By Denise Elliot

The beautiful scarlet cranberry, from the same Vaccinium genus as the blueberry, was first researched in the 17th and 18th centuries and has been used to support the urinary system for many years. Native Americans used cranberry both as a food and for the treatment of kidney and bladder diseases.

With the emergence of more and more antibiotic resistant organisms, the little cranberry is gaining a lot of attention as a possible alternative to antibiotics for the prevention and treatment of urinary tract infections.

The cranberry is not limited to urinary tract infections, it has also been used for prevention of blocked urinary catheters and deodorizing of offensive urine. For use as a urinary deodorizer for incontinent patients, 90 to 180ml per day of cranberry juice was used in a 1966 trial.

Drinking large amounts of cranberry juice may not be the most ideal for health, with commercial products sometimes having a low cranberry content but large sugar and water quantities. Oral capsules or tablets are often the preferred method, and possibly more cost effective. Taken orally, cranberry is generally well tolerated. There have been many clinical trials on cranberry and none reported any significant side effects with 300 to 500mls of cranberry juice consumption daily. Cranberry juice at doses of 3 to 4 litres per day may cause gastrointestinal upset and diarrhoea.

Cranberry juice contains vitamin C, biologically active flavonoids and phenolic compounds. Like the blueberry, they also contain high flavonoids called proanthocyanidins - these are very powerful antioxidants that support a number of body systems including skin health. These flavonoids also may support the vascular system by reducing the risk of atherosclerosis, and in some cases may also decrease LDL cholesterol.

Predominantly though the cranberry is used in the treatment and prevention of urinary tract infections. Years ago it was thought its action was focussing on the ability to lower the pH of the urine. It is now known that cranberry’s active constituents interfere with bacterial adherence to mucosal cells throughout the urinary system. Therefore if the bacteria does not stick to the cells lining the urinary system walls, it is more likely to be able to be passed out via urine.

There are no known interactions of cranberry with herbs or supplements. Interaction with warfarin is possible though, because of cranberry's flavonoids, which may inhibit the enzymes that warfarin is metabolised through. Different commercial brands may affect the drug in different ways. Patients on warfarin would be sensible to limit intake of cranberry and monitor it with their own Doctor or health professional.