The cranberry plant, a familiar source of berries used in juices and relishes in the United States, has been in existence since the Iron Age. The Romans were the first to recognize its medicinal uses by the local inhabitants of what is now England. Herbalist Henry Lyte documented its healing effects in 1578. Since then, the cranberry plant has been a popular folk remedy for a variety of illnesses, including gout, rheumatism, diarrhea, constipation, scurvy, fevers, skin infections and other skin problems such as eczema. Cranberries are well known as a treatment for such women's health problems as cystitis, and urinary and genital infections.
Currently, there are approximately 150 species of cranberry. The best known and most popular is the American
cranberry (Vaccinium macrocarpon), because of the size and juiciness of its fruit. It is a member of the Heath (Ericaceae) family. Vaccinium macrocarpon is a low-lying fruit plant grown commercially in North America. The shrub bears beautiful pink flowers that grow into rounded reddish-black berries. The berries are harvested early in the fall, and made into juices, jellies, or relishes. Juice made from cranberries is a popular, tart fruit drink. The United States presently produces about 98% of the world's cranberries.
Scientists have learned that the chemical composition of cranberries includes many substances that promote healing, such as:
- Proanthocyanidins and anthocyanins. These bioflavenoids make up the pigment of the leaves, and produce the color of the berries. More importantly, proanthocyanidins are responsible for cranberry's best-known medicinal effect, preventing bladder and urinary tract infections by inhibiting bacterial colonization. They may also help relieve diarrheal symptoms.
- Organic acids, including quinic, malic, and citric acids. Quinic acid is considered the most important among these organic acids. These compounds, which are responsible for the sour taste of cranberries, acidify the urine and prevent kidney stones.
- Vitamins and minerals. Cranberries are rich sources of vitamins including vitamin A, carotene, thiamine, riboflavin, niacin, and vitamin C. They also contain many essential minerals such as sodium, potassium, calcium, magnesium, phosphorus, copper, sulfur, iron, and iodide. These vitamins and minerals are strong antioxidants that enable cranberries to help protect the body against such infections as colds or influenza. Because of their high vitamin C content, cranberries were used in the past to prevent a vitamin C deficiency known as scurvy.
- Fiber. Like many other fruits, cranberries are a good source of fiber.
Prevention and treatment of urinary tract infections
Urinary tract infections (UTIs) are extremely common in women, affecting one of every two females during their lifetime. Men have urinary infections as well, but less frequently than women. A woman contracts a urinary tract infection when bacteria gets into the relatively short female urethra and moves up to the bladder. Once in the bladder, the bacteria grow and spread to other parts of the urinary tract. If left untreated, UTIs can cause serious kidney infections that may require hospitalization. The disease is relatively easy to treat, but tends to recur.
In the United States, urinary tract infections result in more than five million medical treatment visits each year. The most frequently prescribed treatment for urinary tract infections is antibiotics. There are also simple self-protective measures that women can take against UTIs. These include:
- Drinking a lot of fluid, which increases the amount of urine produced and helps to flush out infectious microorganisms.
- Emptying the bladder immediately after having intercourse.
- Using oral contraceptives rather than a diaphragm, which tends to put pressure on or irritate the urethra.
- Drinking cranberry juice as a preventive measure for women.
As early as the 1840s, German physicians observed that cranberry juice prevented urinary tract infections. This effect was attributed to the cranberry's high acidity.
Recent research has confirmed the effectiveness of cranberries in preventing UTIs. Two studies in the mid-1990s, one involving women 65 years or older and the other with younger women between the ages of 18 and 45, showed that cranberries are effective in preventing bladder infections. Regardless of age, women can significantly reduce their risk of urinary tract infections by consuming 10 ounces of cranberry juice daily. Scientists, however, have learned that the effectiveness of cranberry juice is not related to its acidity, as was previously believed. Researchers found that the cranberry's antibacterial properties come from its proanthocyanidins (or condensed tannins). Proanthocyanidins inhibit chia coli bacteria from attaching to the inside walls of the bladder, allowing them to be easily flushed out with urine before they multiply and cause infections.
A careful review of all studies involving the cranberry's role in preventing UTIs concluded that cranberry juice or concentrate is beneficial in preventing infections in women, but its benefits have not been proven in children or males. The reviewers also noted that many women did not complete the full one-year study period.
Prevention of kidney stones
Kidney stones are most often caused by high levels of ionized calcium (as in calcium salts) in the urine. Cranberries can help prevent this condition because they are rich in quinic acid, which increases the acidity of the urine. As a result, the levels of ionized calcium in the urine are lowered.
A person needs to drink 16 ounces of unsweetened cranberry juice (two glasses) daily to effectively prevent kidney stones. Cranberry capsules or powdered concentrates are also available. It is important not to consume too much cranberry, because very high acidity in the urine actually increases the risk of kidney stones. A person would need to drink at least one liter of cranberry juice per day for a prolonged period of time for this to occur.
Prevention of colds and influenza
A daily glass of cranberry juice is a good source of vitamin C and antioxidants. These nutrients help support the body's immune function and prevent cancer as well as such common infections as colds or influenza.
Cranberries may serve as a digestive aid. Because of their high acidity, they help to digest fatty foods, and to increase the appetite.
Some early laboratory studies suggest that cranberries may help to prevent gingivitis (gum disease) and coronary (heart) disease. These studies have not yet been confirmed by clinical research in humans.
Cranberry has been a folk remedy for diarrhea. Proponents of this use suggest that the proanthocyanidins in cranberries, in addition to having antibacterial activity, also act as astringents. They cause proteins to clump together to form rigid cakes that prevent bacteria from using the proteins for food. However, the effectiveness of cranberries in the treatment of diarrhea remains unproven.
Various cranberry preparations have also been used to treat skin disorders such as acne, dermatitis, and psoriasis ; bed-wetting; burns and wounds ; and stress and depression. There is currently insufficient scientific evidence to support these uses.
A recent study suggests that cranberry juice may inhibit the formation of dental plaque by preventing bacteria from collecting (coaggregating) on the tooth film formed by proteins in the saliva. These preliminary findings await further testing.
There are many types of cranberry preparations available, partly because cranberry products are among the top 10 best sellers in the health food market. They include:
- Cranberry juice. For prevention of urinary tract infections and kidney stones, recommended products include those containing pure cranberry juice rather than mixtures that are only 25–27% cranberry juice. Four to six ounces of unadulterated cranberry juice daily is recommended for the prevention of UTIs. Some herbalists advocate the use of cranberry for treatment of mild urinary tract infections; dosages of 10–32 oz (0.3–1 kg) daily have been used. Cranberry juice may not be effective, however, for established infections. It should be taken only as a complementary measure rather than as an alternative to antibiotics in the treatment of active UTIs. If a woman experiences such symptoms of cystitis as chills, fever, fatigue, and burning pain during urination, she should contact her doctor immediately for antibiotic treatment.
- Dried cranberry powder capsules (475–500 mg). Because most commercial cranberry juice contains high levels of sugar, these capsules may be a better alternative for diabetic patients or dieters. Each capsule equals 0.5 ounces of cranberry juice. Nine to 15 capsules daily is the recommended dosage for the prevention of urinary tract infections.
- Powdered concentrates. These forms of cranberry are available in different strengths. Women should follow the dosages recommended by manufacturers.
- Fresh or dried cranberries. Dried untreated cranberries can be found in health food stores. They can be stored up to a year. Cranberries are also available fresh or frozen in most grocery stores or supermarkets. Because of their tartness, most people may find it difficult to consume them in sufficient quantity to obtain their therapeutic benefits.
- Cranberry herbal teas. These products can be obtained from health food stores or via the Internet.
Cranberries should be used with care or modification in patients with certain diseases, including:
- Active urinary tract infections. Cranberries should not be substituted for antibiotic treatment, but used only as a supplementary therapy.
- Irritable bowel syndrome (IBS). Large quantities of cranberry juice or capsules may cause diarrhea in IBS patients.
- Diabetes. Patients with diabetes should use sugar-free cranberry juice, or take capsules or powdered concentrates.
There are no identified drug interactions associated with cranberry consumption.
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American Association of Naturopathic Physicians. 601 Valley St., Suite 105, Seattle, WA 98109. (206) 298-0126. Fax: (206) 298-0129. <http://www.naturopathic.org>.
American Herbal Products Association. 8484 Georgia Ave., Suite 370, Silver Spring, MD 20910. (301) 588-1174. <http://www.ahpa.org>.
National Center for Complementary and Alternative Medicine (NCCAM). NCCAM Clearinghouse, PO Box 8218, Silver Spring, MD 20907-8218. (888) 644-6226. Fax: (301) 495-4957. <http://nccam.nih.gov>.
Samuel Uretsky, Pharm.D.