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Cranberry

Botanical name: Vaccinium macrocarpon

Photo

© Steven Foster

Parts used and where grown

Cranberry is a member of the same family as bilberry and blueberry. It is from North America and grows in bogs. The ripe fruit is used medicinally.

Cranberry has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings Health Concerns
2Stars

Urinary tract infection prevention

3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies)

In traditional North American herbalism, cranberry has been used to prevent kidney stones and “bladder gravel” as well as to remove toxins from the blood. Cranberry has long been recommended by herbalists as well as doctors to help prevent urinary tract infections (UTIs).

Active constituents

In test tube studies, cranberry prevents E. coli, the most common bacterial cause of UTIs, from adhering to the cells lining the wall of the bladder. This anti-adherence action is thought to reduce the ability of the bacteria to cause a UTI.1 2 The proanthocyanidins in the berry have exhibited this anti-adherence action.3 Cranberry has been shown to reduce bacteria levels in the urinary bladders of older women significantly better than placebo, an action that may help to prevent UTIs.4 A small double-blind trial with younger women ages 18–45 years with a history of recurrent urinary tract infections, found that daily treatment with an encapsulated cranberry concentrate (400 mg twice per day) for three months significantly reduced the recurrence of urinary tract infections compared to women taking a placebo.5 Other preliminary trials in humans suggest cranberry may help people with urostomies and enterocystoplasties to keep their urine clear of mucus buildup and possibly reduce the risk of UTIs.6 However, one trial found that cranberry did not reduce the risk of UTIs in children with neurogenic bladder disease (a condition that does not allow for proper flow of urine from the bladder) who were receiving daily catheterization.7

How much is usually taken?

One capsule of concentrated cranberry juice extract (400 mg) can be taken two times per day.8 Several 16-ounce (500 ml) glasses of high-quality unsweetened cranberry juice from concentrate each day approximate the effect of the cranberry extract. Cranberry tincture, 1/2–1 teaspoon (3–5 ml) three times per day, can also be taken.

Are there any side effects or interactions?

Cranberry concentrate has not been reported to cause side effects and has no known contraindications to use during pregnancy and breast-feeding. According to one report, supplementation with an unspecified number of cranberry tablets for seven days increased the urinary excretion of oxalate by 43%, suggesting that long term use of cranberry supplements might increase the risk of developing a kidney stone.9 On the other hand, in the same study, urinary excretion of magnesium and potassium (which are inhibitors of stone formation) also increased. Until more is known, individuals with a personal or family history of calcium-oxalate kidney stones should consult a doctor before using cranberry supplements for long periods of time (e.g., more than a week). Cranberry should not be used as a substitute for antibiotics during an acute urinary tract infection, except under medical supervision.

Are there any drug interactions?
Certain medicines may interact with cranberry. Refer to drug interactions for a list of those medicines.

References:

1. Sobota AE. Inhibition of bacterial adherence by cranberry juice: Potential use for the treatment of urinary tract infections. J Urol 1984;131:1013–6.

2. Zafriri D, Ofek I, Adar R, et al. Inhibitory activity of cranberry juice on adherence of type 1 and type P fimbriated Escherichia coli to eucaryotic cells. Antimicrob Agents Chemother 1989;33:92–8.

3. Howell AB, Vorsa N, Der Maderosian A. Inhibition of the adherence of P-fimbriated Escherichia coli to uroepithelial—all surfaces by proanthocyanidin extracts from cranberries. New Engl J Med 1998;339:1005–6.

4. Avorn J, Monane M, Gurwitz JH, et al. Reduction of bacteriuria and pyruria after ingestion of cranberry juice. JAMA 1994;271:751–4.

5. Walker EB, Barney DP, Mickelsen JN, et al. Cranberry concentrate: UTI prophylaxis. J Family Pract 1997;45:167–8 [letter].

6. Leaver RB. Cranberry juice. Prof Nurse 1996;11:525–6 [review].

7. Schlager TA, Anderson S, Trudell J, Hendly JO. Effect of cranberry juice on bacteriuria in children with neurogenic bladder receiving intermittent catheterization. J Pediatr 1999;135:698–702.

8. Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima Publishing, 1996, 57–61.

9. Terris MK, Issa MM, Tacker JR. Dietary supplementation with cranberry concentrate tablets may increase the risk of nephrolithiasis. Urology 2001;57:26–9.

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