Cranberry
Botanical name: Vaccinium macrocarpon
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
Urinary tract infection prevention
Reliable and relatively consistent scientific data showing a substantial
health benefit.
Contradictory, insufficient, or preliminary studies suggesting a health
benefit or minimal health benefit.
For a 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 antiadherence 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 build-up 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 A few 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 Pfimbriated 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–