Author: Winston Craig, MPH, PhD, RD.
The cranberry bush (Vaccinium macrocarpon) is a low-growing evergreen shrub with leathery leaves and bright red berries. This member of the heath family grows in mountains, forests and damp bogs from Alaska to Virginia. However, most of the commercial berries are produced in Massachusetts and Wisconsin.
Native Americans used cranberries for both food and medicine. The berries were enjoyed either raw or sweetened with maple sugar. In addition, they used them in sauces, breads and puddings, and used cranberries in poultices for treating wounds. Cranberry leaves were typically used for diarrhea and urinary disorders. The sailors during colonial days used cranberries to prevent scurvy.
Today, cranberry is available in a variety of products such as frozen cranberries, cranberry juice and juice cocktails, cranberry sauce and capsules containing cranberry powder. Cranberry sauce or jelly are commonly used during the year-end holiday season. The most popular form of cranberries is the sweetened cranberry cocktail that contains about 30 percent cranberry juice. Apple cranberry and other cranberry drinks only contain about 10 percent juice.
Cranberries are distinguished by their extremely sour taste, due to their low sugar and high acid content.
Cranberries are rich in citric, malic, quinic and other acids. They also contain flavonoids, anthocyanins, ellagic acid, and vitamin C. Because of their tannin content, the berries possess a natural astringency.
Help for Infections
Cranberries have longed been considered valuable for maintaining the health of the urinary tract. The juice has been widely used for the prevention, treatment, and symptomatic relief of urinary tract infections.
It was commonly believed that cranberry juice was effective because it acidified the urine. The high acidity was believed to prevent bacterial growth.
However, recent research supports the notion that cranberries contain substances that prevent the adhesion of E coli and other bacteria to the lining of the urinary tract. The bacteria adhere to the urinary tract by way of many fimbriae, hairlike projections on the surface of the bacteria. This allows the bacteria to colonize in large numbers and produce an infection. Recently, researchers identified proanthocyanidins in cranberry juice which inhibit the E. coli from adhering to the lining.
Urinary tract infections (UTIs) pose a serious health problem affecting millions of Americans every year. UTIs are more prevalent among women than in men, and many women will develop several UTIs in their lifetime. The risk of a UTI increases with advancing age, and is greatest among institutionalized older women. In addition, people with diabetes are at higher risk for UTIs.
Symptoms commonly experienced with a UTI include painful urination, the need to frequently urinate, a cloudy urine, and lower back pain. If a UTI is untreated, more serious complications may develop. If they occur during a pregnancy, the infection may cause a pre-term delivery.
A group of 153 elderly women living in a nursing home experienced on average a 50 percent reduction in the bacterial load and white blood cell count in their urine after daily consuming 10 ozs. of cranberry juice cocktail for six months. The elderly women also had a greater possibility of being free of the infection than similar women not using the cranberry juice. Capsules containing cranberry concentrate can also be effective. Women who took two 400 mg capsules of cranberry powder for 3 months experienced a significant decrease in risk of UTIs.
Cranberry juice is also effective in reducing urinary odors in bedridden patients who have urinary infections and are incontinent. Nursing home personnel have observed a decrease in urine odor in the geriatric wards of a nursing home following the regular drinking of two glasses of cranberry juice by the patients. In addition, patients complained less about a burning sensation when they urinated.
What About Other Fruits?
The blueberry (Vaccinium corymbosum), a close relative of the cranberry, is also a good source of the proanthocyanidins which inhibit the colonization of certain bacteria. On the other hand, orange, grapefruit, pineapple, guava, and mango juices do not possess any anti-adhesion properties.
Other Protective Effects
Cranberry appears to possess other benefits for human health. Helicobacter pylori is the major cause of gastric and duodenal ulcers. This bacterium penetrates the mucus lining of the gastrointestinal system and adheres to the underlying epithelial layer. Recently, it was found that a cranberry fraction disabled some strains of H. pylori so that they could not stick to the epithelial surface. Through this mechanism cranberries could help prevent ulcers. A cranberry fraction also reduces the stickiness of oral bacteria and may be useful for delaying the development of dental plaque and gum disease.
Cranberry juice may also prevent the formation of certain types of kidney stones. A glass or two of cranberry juice every day for 1 to 2 weeks will increase the acidity of the urine, and decrease the risk of a kidney stone forming. In addition, cranberry juice does not contain high levels of oxalate, a substance which can promote the formation of kidney stones.
Protection Against Chronic Disease
Cranberries are rich in polyphenolic antioxidants which protect against cancer and cardiovascular disease. The proanthocyanidins and other compounds inhibit the oxidation of LDL cholesterol while cranberry powder has been observed to decrease the LDL cholesterol levels of animals with elevated blood cholesterol levels. The proanthocyanidins in cranberry and lowbush blueberry are known to inhibit tumor growth.
For the prevention or treatment of UTIs a daily glass of cranberry juice, one to three cups of cranberry juice cocktail, or 10-12 capsules of cranberry powder are recommended. Generally there are no side effects. However, drinking 3 or more liters of cranberry juice per day can produce diarrhea and other gastrointestinal effects. Lesser amounts may increase the frequency the bowel movements. It is important that a patient with a UTI see their physician.