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This fact sheet provides basic information about cranberry—common names, what the science says, potential side effects and cautions, and resources for more information.
Cranberries are the fruit of a native plant of North America. These red berries are used in foods and in herbal products. Historically, cranberry fruits and leaves were used for a variety of problems, such as wounds, urinary disorders, diarrhea, diabetes, stomach ailments, and liver problems. More recently, cranberry has been used as a folk or traditional remedy for urinary tract infections or Helicobacter pylori (H. pylori) infections that can lead to stomach ulcers, or to prevent dental plaque. Cranberry has also been reported to have antioxidant and anticancer activity.
The berries are used to produce beverages and many other food products, as well as dietary supplements in the form of extracts, capsules, or tablets.
What the Science Says
- There is some evidence that cranberry can help to prevent urinary tract infections; however, the evidence is not definitive, and more research is needed. Cranberry has not been shown to be effective as a treatment for an existing urinary tract infection.
- Research shows that components found in cranberry may prevent bacteria, such as E. coli, from clinging to the cells along the walls of the urinary tract and causing infection. There is also preliminary evidence that cranberry may reduce the ability of H. pylori bacteria to live in the stomach and cause ulcers.
- Findings from a few laboratory studies suggest that cranberry may have antioxidant properties and may also be able to reduce dental plaque (a cause of gum disease).
- NCCIH is funding studies of cranberry, primarily to better understand its effects on urinary tract infection. The Office of Dietary Supplements and other National Institutes of Health (NIH) agencies are also supporting cranberry research; for example, the National Institute on Aging is funding a laboratory study of potential anti-aging effects.
Side Effects and Cautions
- Drinking cranberry juice products appears to be safe, although excessive amounts could cause gastrointestinal upset or diarrhea.
- People who think they have a urinary tract infection should see a health care provider for proper diagnosis and treatment. Cranberry products should not be used to treat infection.
- There are some indications that cranberry should be used cautiously by people who take blood-thinning drugs (such as warfarin), medications that affect the liver, or aspirin.
- Tell all your health care providers about any complementary health approaches you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care. For tips about talking with your health care providers about complementary health approaches, see NCCIH's Time to Talk campaign.
For More Information
The NCCIH Clearinghouse provides information on NCCIH and complementary health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.
A service of the National Library of Medicine (NLM), PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals.
Office of Dietary Supplements (ODS), National Institutes of Health (NIH)
ODS seeks to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, supporting research, sharing research results, and educating the public. Its resources include publications (such as Dietary Supplements: What You Need to Know), fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements), and the PubMed Dietary Supplement Subset.
PubMed Dietary Supplement Subset: ods.od.nih.gov/Research/PubMed_Dietary_Supplement_Subset.aspx
NIH National Library of Medicine's MedlinePlus
- Cranberry. Natural Medicines Comprehensive Database Web site. Accessed at www.naturaldatabase.com on May 11, 2009.
- Cranberry (Vaccinium macrocarpon). Natural Standard Database Web site. Accessed at www.naturalstandard.com on May 11, 2009.
- Jepson RG, Craig JC. Cranberries for preventing urinary tract infections. Cochrane Database of Systematic Reviews. 2008;(1):CD001321.
- Klein MA. Cranberry (Vaccinium macrocarpon) Aiton. In: Coates P, Blackman M, Cragg G, et al., eds. Encyclopedia of Dietary Supplements. New York, NY: Marcel Dekker; 2005:143–149.
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