Merck Manual

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Cranberry

By

Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Reviewed/Revised Mar 2024
VIEW PROFESSIONAL VERSION

Cranberries are fruit that can be consumed whole or made into food products such as jellies and juices. Cranberry supplements are available as pills.

Claims for Cranberry

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 Antioxidants The human body needs various vitamins and minerals in order to thrive. Many of these nutrients can be found in whole, non-processed foods such as fruits and vegetables. However, most modern... read more 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

Cranberry products taken with warfarin, an anticoagulant, may increase the risk of bleeding; therefore, people taking warfarin should avoid cranberry products. Cranberry may increase the effect of atorvastatin, used to lower cholesterol, as well as nifedipine, an antihypertensive (blood pressure–lowering medication).

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

Drugs Mentioned In This Article

Generic Name Select Brand Names
Coumadin, Jantoven
Atorvaliq, Lipitor
Adalat, Adalat CC, Afeditab CR, Nifediac CC, Nifedical XL, Procardia, Procardia XL
NOTE: This is the Consumer Version. DOCTORS: VIEW PROFESSIONAL VERSION
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