Cranberries are fruit that can be consumed whole or made into food products such as jellies and juices. Cranberry supplements are available as pills.
(See also Overview of Dietary Supplements.)
Claims for Cranberry
People most often take cranberries to help prevent and relieve the symptoms of urinary tract infections (UTIs).
Some people take cranberry juice to reduce fever and treat certain cancers, specifically stomach cancer caused by the bacterium Helicobacter pylori. Proponents claim cranberry has an antioxidant effect. Antioxidants protect cells against damage by free radicals, which are highly chemically active by-products of normal cell activity.
Evidence for Cranberry
Evidence suggests that cranberry juice or extract can help prevent UTIs from recurring during the following 12 months, but this effect is small. Cranberry cannot treat active UTIs. However, evidence has been somewhat inconsistent. Natural unprocessed cranberry juice contains anthocyanidins, which prevent Escherichia coli (the bacteria that usually cause urinary tract infections) from attaching to the urinary tract wall.
There is no evidence that cranberry is effective for reducing fever or treating certain cancers.
Side Effects of Cranberry
No side effects are known. However, because most cranberry juice is highly sweetened to offset its tart taste, people with diabetes should not consume cranberry juice unless it is artificially sweetened or unsweetened. People can also avoid the extra sugar by using cranberry pills instead of food products.
People who have kidney stones should consult their doctor before taking cranberry products.
Drug Interactions with Cranberry
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Recommendations for Cranberry
People with recurring UTIs can consider taking cranberry to reduce the risk. However, they should consult their doctor about possible medication interactions before taking cranberry products.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institutes of Health's National Center for Complementary and Integrative Health: Cranberry
