Merck Manual

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Cranberry

By

Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Last full review/revision Jan 2022| Content last modified Sep 2022
CLICK HERE FOR THE PROFESSIONAL VERSION

What is cranberry?

What claims are made about 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.

Does cranberry work?

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.

What are the possible 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.

What drug interactions occur 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 drug).

Recommendations

People with recurring UTIs can consider taking cranberry to reduce the risk. However, they should consult their doctor about possible drug interactions before taking cranberry products.

NOTE: This is the Consumer Version. DOCTORS: CLICK HERE FOR THE PROFESSIONAL VERSION
CLICK HERE FOR THE PROFESSIONAL VERSION
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