Cranberry (Vaccinium Macrocarpon)

Medical Uses

Cranberries are used to prevent urinary tract infections and to treat mild urinary tract infections.

Historical Uses

Native Americans and Europeans who settled in the United States used cranberries for food and medicinal purposes. Around 1923, scientists discovered that people who consumed cranberries had more acidic urine than those who did not.


The cranberry is related to the blueberry and bilberry. Cranberries prefer bogs, cool weather, and acidic soils.

Cranberry: Part Used

• Fruit (red berries)

Major Chemical Compounds

• Proanthocyanidins

• Flavonoids

• Fructose

• Vitamin C

Cranberry: Clinical Uses

Cranberries are used to prevent urinary tract infections (UTIs) and are useful in treating mild UTIs.

Mechanism of Action

Cranberry prevents the adherence of bacteria to the walls of the urinary tract because the fructose compound inhibits adhesion of Escherichia coli () and proanthocyanidins inhibit adhesion of E. coli to uroepithelial cells.

Cranberry: Dosage

Capsules: 300 to 400 mg twice a day of standardized, concentrated cranberry extract capsules.

Berries or juice: The daily amount needed is IV2 ounces of fresh or frozen cranberries or 3 ounces of cranberry juice. For prevention, use one daily serving of cranberries or cranberry juice cocktail. For treatment, 4 to 10 servings, or up to 32 ounces per day, may be needed.

Side Effects

None are known.


None are known.

Herb-Drug Interactions

None are known.

Pregnancy and Breast-Feeding

Cranberries are safe if used as recommended.

Summary of Studies

Avorn et al. (1994) In this 6-month, double-blind, placebo-controlled study, 153 women drank 300 mL of cranberry juice cocktail or a synthetic placebo drink with a similar flavor but no cranberry content each day. Results: Regular intake of cranberry juice cocktail significantly reduced the frequency of bacteriuria and pyuria in elderly women.

Kontiokari et al. (2001). This was an open, randomized 12-month follow-up of 150 women with UTIs caused by Escherichia coll The women were divided into three groups: the first group drank cranberry-lingonberry juice; the second a lactobacillus GG drink, and the third a placebo drink. The recurrence of UTIs was reduced in the first group only.


• None are known.

• Cranberries are safe if used as recommended for pregnant and breast-feeding women.