Cranberry: Benefits, Dosage, and Safety

What cranberry is

Cranberry is the fruit of an evergreen shrub (Vaccinium macrocarpon, and the related Vaccinium oxycoccos) native to wet habitats of northeastern and north-central North America. It has a long history of traditional use among Native Americans and European settlers as food, dye, and medicine. As a dietary supplement it is sold as juice, juice cocktail, dried fruit, powder, tablets, and capsules. Its most studied constituents are proanthocyanidins (PACs), a class of polyphenols also called condensed tannins. Cranberry PACs are notable for containing A-type linkages, a structural feature shared by few other foods. Cranberry is not a nutrient and has no essential role in human physiology, so no Dietary Reference Intake has been set for it.

What it does

• Supplies polyphenols called proanthocyanidins (PACs), which in laboratory studies are thought to keep certain bacteria (P-fimbriated E. coli) from sticking to the cells that line the bladder wall
• Provides an acidic, polyphenol-rich fruit food matrix (organic acids, glucose, fructose, vitamin C, and anthocyanins) as part of the diet
• Studied as a nonantibiotic approach that may lower the risk of symptomatic, recurrent urinary tract infections in some women at increased risk

Intake and dosing

Cranberry is not an essential nutrient, so no Recommended Dietary Allowance or Tolerable Upper Intake Level has been set. Doses in studies vary widely. Because supplement doses are not standardised, discuss an appropriate amount with a clinician or pharmacist.

Deficiency and who is at risk

Not applicable. Cranberry is not an essential nutrient, so there is no deficiency state or deficiency disease associated with lack of dietary cranberry.

Who may need more

• Women with a history of recurrent urinary tract infections who, with their clinician, wish to try a nonantibiotic prevention option (NIH/NCCIH notes benefit is uncertain and inconsistent)
• People interested in reducing antibiotic use for recurrent UTI prevention
• No one needs cranberry nutritionally; it is not an essential nutrient and there is no requirement to consume it

Food sources

Whole cranberries and 100% cranberry juice are the richest sources; also cranberry juice cocktail (typically 25-27% juice), dried sweetened cranberries, and cranberry sauce. Related Vaccinium fruits (for example lingonberry) contain similar polyphenols. Cranberries are about 90% water and also supply vitamin C, organic acids (quinic, malic, citric), and anthocyanins.

Forms and absorption

Available as cranberry juice, sweetened juice cocktail, dried fruit, whole-fruit powder, standardized extracts, tablets, and capsules. NIH/NCCIH cautions that processing cranberries into products such as tablets or capsules can reduce the concentration of proanthocyanidins (PACs), which may reduce a product's potential effectiveness; some products may contain little or no PAC. PAC content is not standardized across products and is often not stated on the label, so potency varies widely.

Safety, excess and interactions

Too much

According to NIH/NCCIH, cranberry taken orally is generally thought to be safe, but consuming very large amounts can cause stomach upset and diarrhea, particularly in young children. There is no established Tolerable Upper Intake Level.

Interactions to know

• Warfarin (anticoagulant): NIH/NCCIH reports conflicting evidence about whether cranberry interacts with warfarin; some case reports and warfarin product labeling raise concern about a possible increased INR and bleeding risk, while several randomized studies found no significant pharmacodynamic interaction. Anyone taking warfarin should talk with their health care provider before using cranberry.
• General medicines: NIH/NCCIH advises that some herbs and medicines interact in harmful ways, so people taking any medication should consult their provider before using cranberry products.
• Some professional references note cranberry may increase the effect of medicines metabolized by CYP2C9 or CYP3A (for example atorvastatin, nifedipine); evidence is limited and not confirmed by NIH.

How status is measured

Not routinely measured. There is no clinical blood or urine test for cranberry or PAC status. In research, cranberry potency is characterized by proanthocyanidin (PAC) content, commonly quantified by the DMAC (4-dimethylaminocinnamaldehyde) method; anti-adhesion activity is sometimes assessed ex vivo in urine.

Regulated as a dietary supplement (and as a food/juice) under DSHEA, not approved by the FDA before sale. In July 2020 the FDA issued a letter of enforcement discretion allowing a qualified health claim that consuming certain amounts of cranberry dietary supplements may reduce the risk of recurrent UTIs in healthy women, with the evidence described as 'limited'; a similar claim for cranberry juice beverages must describe the evidence as 'limited and inconsistent.' Cranberry is not an FDA-approved drug and may not be marketed to diagnose, treat, cure, or prevent disease.

What the evidence supports

We grade the strength of evidence behind each common reason people take cranberry, mirroring how the NIH describes it.