Cranberry

Background

• Cranberry is an evergreen shrub that grows in wet habitats in the Northeastern and North Central parts of North America.
• Cranberry has a history of traditional use in dyes, food, and medicine among Native Americans and later European settlers. Cranberry fruits and leaves were thought to have therapeutic effects on disorders of the bladder, stomach, blood, and liver, and on various conditions like wounds, diabetes, and scurvy.
• Today, cranberry is commonly promoted for urinary tract infections (UTIs) and recurrent UTIs. Cranberry products are promoted for these common infections in part because of a growing interest in nonantibiotic prevention strategies, given concerns about antibiotic-resistant bacteria.

How Much Do We Know?

• There have been many studies on cranberry for the prevention of UTIs, especially among women at increased risk for UTIs or recurrent UTIs. However, some research isn’t of high quality.
• There’s little research on cranberry for other conditions.

What Have We Learned?

• In general, cranberry products may decrease the overall risk of symptomatic, recurrent UTIs in women by 25 percent, and in some cases, by more than 30 percent. However, the effectiveness of cranberry is still in question because of inconsistent findings.
• While cranberry may assist in preventing symptomatic UTIs in some women, it isn’t recommended as a treatment for existing UTIs in any population.
• It’s thought that the proanthocyanidins (PACs) present in cranberries prevent bacteria from sticking to the bladder wall, thus preventing the start of a UTI. Processing cranberries into various products, like tablets or capsules, can reduce the concentration of PACs, which can reduce the potential effectiveness of a product.
• Studies in certain populations at increased risk for UTIs, such as elderly people in long-term care and pregnant women, have had inconsistent results. 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 reducing the risk for UTIs.
• Starting in 2020, the U.S. Food and Drug Administration has allowed 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 UTIs in healthy women. A similar claim may be made for cranberry juice beverages, but the evidence must be described as “limited and inconsistent.”

What Do We Know About Safety?

• Cranberry taken orally (by mouth) is generally thought to be safe. However, if consumed in very large amounts, cranberry can cause stomach upset and diarrhea, particularly in young children.
• People who think they have a UTI should see a health care provider for diagnosis and treatment. Don’t use cranberry products instead of a proven treatment for a UTI.
• There is conflicting evidence about whether cranberry interacts with the anticoagulant (blood thinner) warfarin. If you take warfarin or any other medicine, talk with your health care provider before using cranberry or other herbal products; some herbs and medicines interact in harmful ways.
• Some studies of the use of cranberry during pregnancy or while breastfeeding suggest it is safe in amounts commonly found in food, but the evidence is not conclusive for use in larger amounts. If you’re considering using cranberry while pregnant or breastfeeding, consult your health care provider. 

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.

• Federal Regulation of Herbal Products
  • Depending on what’s in them, how they’re intended to be used, and how they’re administered (orally or topically), herbal products are regulated in a variety of ways. Many herbal products intended for oral use are marketed as dietary supplements. The rules for making and distributing dietary supplements are less strict than those for drugs.
  • Unlike drugs, dietary supplements are not approved by the FDA before they are sold to the public. When public health concerns arise about the safety of a dietary supplement or an ingredient including an herb, the FDA can take action to protect the public. Manufacturers and distributors of supplements are responsible for evaluating the safety and labeling of their products before marketing to ensure that they meet all regulatory requirements.

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