In the United States, urinary tract infections account for a significant number of the bacterial infections suffered each year. Perhaps only strep throat accounts for more. By some estimates, as many as 50 million cases of urinary tract infections are treated annually. Although these infections aren't considered life-threatening or even a significant health risk for most people, their financial toll is enormous. Medication for each episode can cost about $30 and a visit to a physician, at least $40. Include time missed from work, and urinary tract infections cost billions of dollars a year.

Health-care providers have relied primarily upon antibiotics to treat urinary tract infections. However, increasing concern about bacterial resistance to antibiotics and rising interest in alternative medicine have prompted doctors and researchers to seek new treatments. Recent studies suggest that cranberry (Vaccinium macrocarpon), long reputed to have antibacterial properties, may have the potential to prevent or heal these expensive and painful infections.

Cranberry then and now
As early as the 1840s, German researchers were examining the connection between European cranberry species and urinary tract infections. They found that the urine of people who ate cranberries contained a chemical called hippuric acid. By the turn of the century, U.S. researchers were speculating that this attribute meant that cranberries could acidify urine and thereby prevent infection. By the 1960s, however, the idea of using cranberry to treat such infections had fallen out of favor because researchers failed to show that it increased urine acidity enough to prevent illness. Today, researchers are again addressing the relationship between cranberries and a healthy urinary tract, only this time they are focusing on a different action: cranberry's potential to keep bacteria from attaching to urinary tract walls.

How infection begins
These infections are generally divided into three categories. Urethritis is an infection of the urethra, the canal that transports urine from the bladder and in males also serves as a genital duct. The infection is usually caused by viruses transmitted during intercourse. Cranberry can't be used to prevent or treat this condition because it is not effective against viral infections. Cystitis is an infection of the urinary bladder, the organ that stores urine. Pyelonephritis, or kidney infection, results when the bacteria in the bladder migrate to the kidneys. This type of infection is the most serious of the three; it is often accompanied by fever, chills, nausea, and severe back pain. Current cranberry research is focusing on cystitis and pyelonephritis because they are caused by the bacteria Escherichia coli (E. coli).

E. coli serve a positive purpose in the large intestine, where they break down the by-products of digestion. However, they also are responsible for about eighty-five percent of all urinary tract infections. E. coli, which enter through the perineum and travel through the urethra up to the bladder, attach themselves to cells in the bladder wall, where they reproduce, colonize, and cause a bladder infection. Because this infectious process starts to destroy the superficial lining of the bladder and disrupts the small capillaries, urine of infected individuals often contains blood. If the infection progresses, the E. coli will then travel up the urethers and infect the kidneys.