History and Cultural Significance

The Iroquois and the Cherokee tribes viewed the cranberry as a symbol of peace and friendship.³ Historically, cranberries were used by American settlers in poultices for treating wounds and blood poisoning and were eaten to prevent scurvy (a disease caused by vitamin C deficiency).⁴ Cranberries and their leaves were used for treating various conditions including stomach ailments, liver problems, fever, swollen glands, and mumps.

Traditionally, the fruit has also been used to treat urinary tract infections³ and as a urinary deodorizer for people with incontinence.⁵ In foods, cranberries are used widely in fruit juice, jelly, and sauce.

Modern Research

At least 21 studies have been conducted on a total of more than 1700 subjects demonstrating cranberry’s positive effects on urinary tract health. Of these, 9 studies supported the use of cranberry juice or capsules for the prevention of urinary tract infections (UTI).^{6,7,8,9,10,11,12,13,14} Two of the studies found cranberry juice to be effective in the treatment of UTIs,^15,16 while 2 additional studies on elderly subjects examined cranberry juice as a treatment for bacteriuria (bacteria in the urine, with or without UTI) and pyuria (pus or white blood cells in the urine).^17,18 Eight studies investigated the effect of fresh cranberry juice on urinary pH and kidney stones.^{19,20,21,22,23,24,25,26}

Early research suggested that cranberry juice acidified the urine through the excretion of hippuric acid, thus inhibiting the growth of bacteria.²⁷ However, later studies showed that cranberry’s effectiveness in treating UTIs is due to its inhibition of the adhesion of

E. coli bacteria to the walls of the urinary tract, thereby preventing colonization of the bacteria and subsequent infection.^28,29,30,31 The authors of a 2007 study investigated the effects of 2 cranberry products on bladder epithelial cells as well as vaginal epithelial cells.²⁷ (Note: The brand of one of the cranberry products used in the study was not identified and the other was a purified cranberry extract prepared in a laboratory.) These are the first published results on the ability of cranberry to inhibit E. coli adhesion to vaginal epithelial cells. The results suggest that cranberry has the potential to inhibit adherence to both vaginal epithelial cells and bladder epithelial cells, thus preventing UTIs before colonization in the bladder.²⁷

Recent case reports suggest the possible adverse interaction of cranberry with the anticoagulant drug warfarin (aka Coumadin®, Bristol-Myers Squibb).^{32,33,34,35,36} Based on these reports, the United Kingdom’s Committee on Safety of Medicines alerted clinicians to advise patients to avoid the concurrent use of cranberry and warfarin.^33,37 Patient education materials in US pharmacies have also recommended that patients limit intake or avoid cranberry consumption while taking warfarin.³⁷ However, some sources consider this a dubious interaction.^38,39 David Greenblatt, MD, of Tufts University Medical School reviewed all the case reports and stated that “not a single one of these cases plausibly demonstrated that loss of anticoagulant control was caused by cranberry juice.”³⁹ Also, Greenblatt did a clinical study on patients taking cranberry juice and flurbiprofen and found no effect of cranberry on the metabolism of flurbiprofen, suggesting no interaction between cranberry and warfarin.^39,40 (Note: Flurbiprofen is a drug that is metabolized by the CYP2C9 enzyme, which also plays a major role in warfarin metabolism.)

Future Outlook

As recently as June 2001, overproduction had diminished the price of cranberries.⁴¹ However, due to its increasingly well-documented health benefits, cranberry has attracted widespread media and industry attention in recent years. Moving from beverages and mineral waters into dairy and confectionary products, cranberry is now also recognized as a key ingredient in the dietary supplement market.^2,42 Because of the increased awareness on the importance of healthy nutrition, the future of cranberry as a food and dietary supplement appears certain, and it may eventually become a recognized medicinal product.

—Gayle Engels

References

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