Cranberry is native to eastern North America, where it prefers very moist habitats, such as bogs, with acidic soil. The plant is a low, sprawling shrub bearing small clusters of attractive pink to white flowers with elongated, recurved corolla lobes and protruding anthers. The red, fleshy edible berries are mostly used for the manufacture of cranberry juice (usually mixed with other juices because of its strongly acidic taste) and products such as cranberry sauce. The genus Vaccinium includes about 450 species, distributed over most of the world, many of which are valued at least locally for their edible fruits. Bilberries, blueberries, cowberries, farkleberries, lingonberries, partridgeberries, and huckleberries are among the many fruits derived from this genus. Cranberry is an important crop in areas of the northern United States and Canada, where mechanized methods of cultivation and harvest have been developed. Like many berries, cranberry is rich in antioxidants. Its most common medicinal use is for prevention of urinary tract infections.

High-quality human clinical trials have shown that cranberry juice and tablets or capsules reduce the frequency of recurrent urinary tract infections (UTIs). (At least three placebo-controlled studies have compared cranberry juice to a placebo ?juice? beverage.) However, studies of people with neurogenic bladder following spinal cord injury have found that cranberry capsules and tablets do not prevent recurrent UTIs in people with that condition. Lab and human studies have shown that cranberry prevents UTIs at least in part by preventing adhesion of bacteria such as E. coli to the lining of the urinary tract. It is possible that this activity may offer other benefits, such as reducing the formation of dental plaque; two studies have found that cranberry may help to suppress Helicobacter pylori stomach infection, although its efficacy is limited. Because cranberry is a conventional food or beverage regularly consumed by many people, it is presumed to be safe for consumers including pregnant women and children, as available scientific evidence also indicates. Anecdotal reports have suggested that cranberry might interact with warfarin to increase the risk of bleeding caused by that drug. However, four human studies have shown that cranberry juice at doses of 240 to 600 ml (8 to 20 oz.) per day does not affect the pharmacokinetics of warfarin or similarly metabolized drugs.

Selected References

Avorn, J., M. Monane, J. H. Gurwitz, R. J. Glynn, I. Choodnovskiy, and L. A. Lipsitz. 1994. Reduction of bacteriuria and pyuria after ingestion of cranberry juice. JAMA 271: 751-754.

Bruederle, L. P., M. S. Hugan, and J. M. Dignan. 1996. Genetic variation in natural populations of the large cranberry, Vaccinium macrocarpon Ait. (Ericaceae). Bull. Torrey Bot. Club. 123: 41-47.

Di Martino, P., R. Agniel, K. David, C. Templer, J. L. Gaillard, P. Denys, and H. Botto. 2006. Reduction of Escherichia coli adherence to uroepithelial bladder cells after consumption of cranberry juice: a double-blind randomized placebo-controlled cross-over trial. World J. Urol. 24: 21-27.

Dugoua, J. J., D. Seely, D. Perri, E. Mills, and G. Koren. 2008. Safety and efficacy of cranberry (Vaccinium macrocarpon) during pregnancy and lactation. Can. J. Clin. Pharmacol. 15: e80-86.

Jepson, R. G., and J. C. Craig. 2007. A systematic review of the evidence for cranberries and blueberries in UTI prevention. Mol. Nutr. Food Res. 51: 738-745.

Lee, B. B., M. J. Haran, L. M. Hunt, J. M. Simpson, O. Marial, S. B. Rutkowski, J. W. Middleton, G. Kotsiou, M. Tudehope, and I. D. Cameron. 2007. Spinal-injured neuropathic bladder antisepsis (SINBA) trial. Spinal Cord 45: 542-550.

Li, Z., N. P. Seeram, C. L. Carpenter, G. Thames, C. Minutti, and S. Bowerman. 2006. Cranberry does not affect prothrombin time in male subjects on warfarin. J. Am. Diet. Assoc. 106: 2057-2061.

Lilja, J. J., J. T. Backman, and P. J. Neuvonen. 2007. Effects of daily ingestion of cranberry juice on the pharacokinetics of warfarin, tizanidine, and midazolam ? probes of CYP2C9, CYP1A2, and CYP3A4. Clin. Pharmacol. Ther. 81: 833-839.

Ogle, D. W. 1984. Phytogeography of Vaccinium macrocarpon Aiton in the southern United States. Virg. J. Sci. 35: 31-47.

Stothers, L. 2002. A randomized trial to evaluate effectiveness and cost effectiveness of naturopathic cranberry products as prophylaxis against urinary tract infection in women. Can. J. Urol. 9: 1558-1562.

Vander Kloet, S. P. 1983. The taxonomy of Vaccinium section Oxycoccus. Rhodora 85: 1-43.

Vander Kloet, S. P. 1988. The Genus Vaccinium in North America. Research Branch, Agriculture Canada, Ottawa.

Yamanaka, A., R. Kimizuka, T. Kato, and K. Okuda. 2004. Inhibitory effects of cranberry juice on attachment of oral streptococci and biofilm formation. Oral Microbiol. Immunol. 19: 150-154.