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.
• Recently, cranberry products have been used in the hope of preventing or treating urinary tract infections or Helicobacter 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, teas, and capsules or tablets.

What the Science Says

• Some studies testing cranberry products for their ability to prevent urinary tract infections have shown promise. These studies have generally been small in size, and some were not randomized or controlled; therefore, the results are not conclusive.
• Cranberry products have not been adequately tested to see if they can be used to help treat 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. However, the mechanism of action of cranberry is not fully understood.
• NCCAM, the National Institute of Diabetes and Digestive and Kidney Diseases, and the National Institute for Dental and Craniofacial Research are funding studies to understand whether and how cranberry might work to:
  • Prevent urinary tract infection
  • Prevent the formation of dental plaque

Side Effects and Cautions