Cranberry

Background

• Cranberry is an evergreen shrub that grows in wet habitats in the Northeastern and North Central parts of the United States.
• Historically, cranberry fruits or leaves were used for bladder, stomach, and liver disorders, as well as diabetes, wounds, and other conditions.
• Today, cranberry is most commonly promoted for urinary tract infections (UTIs).

How Much Do We Know?

• There have been many studies in people of cranberry for UTIs, but there’s little research on cranberry for other conditions.

What Have We Learned?

• ​​​​In general, studies in people who are at increased risk for UTIs or those who have had recurrent UTIs show that cranberry products decrease the risk of UTIs by about one-third. However, there’s still some uncertainty about the effectiveness of cranberry because some of the research has not been of high quality. Also, studies in certain populations at increased risk of UTIs, such as elderly people in long-term care and pregnant women, have had inconsistent results, and studies in other high-risk populations, such as women undergoing gynecological surgeries or people with multiple sclerosis, have not found cranberry to be beneficial.
• In 2020, the U.S. Food and Drug Administration announced that it would permit manufacturers to claim on product labels that there is “limited” evidence that daily consumption of specified amounts of cranberry dietary supplements may reduce the risk of recurrent UTI in healthy women who have had a UTI. A similar claim may be made for cranberry juice beverages, but the evidence must be described as “limited and inconsistent.”  
• Cranberry hasn’t been shown to be effective as a treatment for an existing UTI.
• NCCIH-supported research is looking at the effects of polyphenols from cranberry and other fruits and vegetables on the gut microbiome, to see whether these effects may play a role in the association between consumption of these foods and reduced risk of chronic diseases.

What Do We Know About Safety?

• Cranberry products are generally thought to be safe. However, if consumed in very large amounts, they can cause stomach upset and diarrhea, particularly in young children.
• Little is known about whether it’s safe to use cranberry for health purposes during pregnancy or while breastfeeding.
• There is conflicting evidence about whether cranberry interacts with the anticoagulant (blood thinner) warfarin.
• People who think they have a UTI should see a health care provider for diagnosis and treatment. Don’t use cranberry products in place of proven treatment for a UTI.

Keep in Mind

• Take charge of your health—talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

For More Information

• Using Dietary Supplements Wisely
• Know the Science: How Medications and Supplements Can Interact
• Know the Science: How To Make Sense of a Scientific Journal Article

Key References