The cranberry is a member of the plant family Ericaceae, which includes a number of edible berries such as blueberries, huckleberries, and bilberries. The plant is an evergreen, fruit-bearing vine found in bogs and swamps throughout much of Europe, Asia, and North America. Most commercially grown cranberries are produced in bog fields in New England, Wisconsin, Washington, Oregon, and Eastern and Central Canada. The primary cultivated species, Vaccinium macrocarpon, is a woody vine that produces stems or runners which can reach lengths of six feet or more. From these runners grow short upright branches (about two to three inches long) which bear the flowers and fruit. The small (7-13 mm long and 2-6 mm wide), oval-shaped leaves stay on the plant about two years and vary in color from dark, glossy green during summer to a dull, reddish brown during the dormant winter months. The plant flowers from June through July, producing small, pale-rose colored blossoms. The bitter-tasting fruit, which are bright red in color and nearly spherical in shape, are used widely as a food and are also used for health-promoting purposes.
Most of cranberry's activity in the body is attributed to its concentration of proanthocyanidins, a group of antioxidant flavonoids found in red, blue, and purple colored berries. Cranberry also contains vitamin C and (in trace amounts) a variety of other essential vitamins and minerals.
The optimum dosage of cranberry juice for UTIs has yet to be determined. Because many commercial cranberry drinks (cranberry juice cocktails) contain less than 30 percent cranberry juice, and most are heavily sweetened with sugar, many herbalists recommend using concentrated (10:1) cranberry capsules or tablets in doses equivalent to 1,600 mg per day. Cranberry juice has no known toxicity and appears to be very safe, with no negative side effects reported at this dosage. Increasing intake of fluids is often recommended for people taking cranberry supplements. Cranberry should not be used as a substitute for antibiotics during acute urinary tract infection. Because acute urinary tract infections can be dangerous, even lethal, they should be diagnosed and treated by a physician.