Tannins Found in Cranberries Act as Antibacterial Agents

Researchers are now proving what doctors have known for years. Cranberries contain antibacterial qualities that are effective in treating urinary tract infections, stomach ulcers, and more. Worcester Polytechnic Institute (WPI) researchers have found that tannins in cranberries have the ability to alter E. coli bacteria. These tannins, called proanthocyanidins or PACs, prevent E. coli from adhering to cells in the body thereby preventing infection. These PACs are present in cranberry juice and other cranberry products.

It has long been know that cranberry juice is effective at preventing urinary tract infections (UTIs). The conventional, though unproven, thought was that the cranberry juice caused the E. coli bacteria to lose its stickiness and get washed away in urine. However, the mechanisms which underlie the health benefits of cranberries and its products have been unknown. Now, through the use of atomic force microscopes and other tools it is becoming clear that PACs interact with E. coli on a molecular level.

Terri Camesano, Associate Professor of Chemical Engineering at WPI, headed the cranberry research team which found that cranberry juice causes an energy barrier that keeps bacteria from getting close to the urinary tract lining. This reduction in adhesion is found when at least a five percent solution of cranberry juice cocktail is present. In addition, E.coli grown in cranberry juice are unable to form biofilms. Biofilms are clusters of high concentrations of bacteria and are required for infections to develop, especially with indwelling catheters and other biomedical devices. Cranberry juice also inhibits the ability of E.coli to produce a molecule, IAA, which is used by bacteria as a way to communicate their location to other bacteria. The presence of IAA enables bacteria to sense whether their population is large enough to form a biofilm or initiate an infection.

PACs have substantial antioxidants and as a plant compound protect the plant from harmful intruders such as fungi, microbes, and animals. PACs are called tannins because of their earlier use in the tanning industry to convert animal hides to leather. In addition to cranberries, PACs are found in berries, red grapes, red wines, cinnamon, and baking chocolate. According to Pharmaceutical Biology, the PACs in cranberries and cinnamon have been found to have antibacterial adhesion qualities and improve glucose metabolism in Type 2 diabetes.

Camesano is currently working on determining the minimum effective dose and frequency of consumption necessary to ward off infections. Previous studies reported in Urology Times have shown that drinking eight ounces of juice result in a 71% reduction in the amount of E. coli bacteria that attached to the bladder wall. A four ounce serving led to a reduction of 33%.

Cranberries are also being investigated for their abilities to reduce cancer and cardiovascular disease. Nutrition Reviews cites evidence suggesting the use of cranberries also prevent stomach ulcers and improve oral hygiene. Again, these antibacterial qualities are due to the PACs ability to reduce the adhesion of bacteria to stomach lining and tooth surfaces.

Sources:
Worcester Polytechnic Institute, "Cranberry Sauce:Good for What Ails You", Eurekalert.

McKay, Diane and Jeffrey L. Blumberg. "Cranberries (Vaccinium macrocarpon) and Cardiovascular Disease Risk Factors." Nutrition Reviews 65 (2007):490-502.

Beecher, Gary, "Proanthocyanidins: Biological Activities Associated with Human Health.", Pharmaceutical Biology 42 (Supp.) (2004): 2-20.

"Drinking More Cranberry Juice May Help Prevent UTIs." Urology Times 32.16 (Nov 2004):20. General OneFile. Gale. Las Vegas Clark County Library District. 13 Nov. 2007 .