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.
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3 Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2 Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.
500 mg three times per day after meals
Supplementing with a cranberry extract has been shown to help lower total and LDL ("bad") cholesterol in people with type 2 diabetes taking hypoglycemic medication.
In a double-blind trial, supplementation with a cranberry extract (500 mg three times per day after meals) for 12 weeks significantly lowered serum total cholesterol and LDL cholesterol levels compared with placebo in patients with type 2 diabetes who were taking oral hypoglycemic medication.1
1,500 mg per day of dried cranberry powder for six months
A preliminary study found that dried cranberry powder improved urinary symptoms in men with prostatitis.
In a preliminary study, treatment with 1,500 mg per day of dried cranberry powder for six months improved urinary symptoms in men with chronic nonbacterial prostatitis.2
Urinary Tract Infection
4 to 10 ounces (114 to 296 ml) of cranberry juice daily or 400 mg of powdered cranberry concentrate twice per day
Supplementing with cranberry has been shown to help treat and prevent recurrences.
Modern research has suggested that cranberry may prevent urinary tract infections.3 , 4 In a double-blind trial, elderly women who drank 10 ounces (300 ml) of cranberry juice per day had a decrease in the amount of bacteria in their urine.5 In another study, elderly residents of a nursing home consumed either four ounces (120 ml) of cranberry juice or six capsules containing concentrated cranberry daily for 13 months. During that time, the number of UTIs decreased by 25%.6 A small preliminary trial found that supplementation with encapsulated cranberry concentrate (400 mg twice per day for three months) significantly reduced the recurrence of UTIs in women (aged 18 to 45) with a history of recurrent infections.7
Cranberry juice has also been found to be as effective as the antibiotic cefaclor for preventing UTIs in children who had recurrent UTIs because of a condition that causes urine to flow backwards from the bladder into the ureters (vesicoureteral reflux). In that study, the children received a cranberry juice concentrate that was equivalent to 200 ml of cranberry juice per day.8
Research has suggested cranberry may be effective against UTIs because it prevents E. coli, the bacteria that causes most urinary tract infections, from attaching to the walls of the bladder.9 Cranberry is not, however, a substitute for antibiotics in the treatment of acute UTIs. Moreover, in children whose UTIs are due to “neurogenic bladder” (a condition caused by spinal cord injury or myelomeningocele), cranberry juice supplementation did not reduce the rate of infection.10 Drinking 10–16 ounces (300–500 ml) of unsweetened or lightly sweetened cranberry juice is recommended by many doctors for prevention, and as part of the treatment of UTIs. Alternatively, 400 mg of concentrated cranberry extracts twice per day can be used.
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.11 , 12 The proanthocyanidins in the berry have exhibited this anti-adherence action.13 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.14 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.15 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.16 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.17
One capsule of concentrated cranberry juice extract (400 mg) can be taken two times per day.18 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.
Certain medicines interact with this supplement.
People taking omeprazole may increase absorption of dietary vitamin B12 by drinking cranberry (Vaccinium marocarpon) juice or other acidic liquids with vitamin B12-containing foods.20
Omeprazole was shown to reduce protein-bound vitamin B12 absorption and cranberry (Vaccinium macrocarpon) juice was shown to increase protein-bound vitamin B12 absorption in eight people treated with omeprazole (a drug closely related to lansoprazole).19 While this effect has not been studied with lansoprazole, people taking lansoprazole may choose to drink cranberry juice or other acidic liquids with vitamin B12-containing foods. Unlike vitamin B12 found in food, vitamin B12 found in supplements is not bound to peptides (pieces of protein). The absorption of B12 supplements therefore does not require acid and is unlikely to be improved by drinking cranberry juice.
There have been at least five case reports suggesting that cranberry juice increases the activity of warfarin, possibly by inhibiting the breakdown of warfarin in the body.21 Because of this potential interaction, people taking warfarin should avoid, or limit the intake of, cranberry juice. The U.K. Medicines Authority has advised people taking warfarin to avoid cranberry juice.
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.22 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.
1. Lee IT, Chan YC, Lin CW, et al. Effect of cranberry extracts on lipid profiles in subjects with Type 2 diabetes. Diabet Med 2008;25:1473-7.
2. Vidlar A, Vostalova J, Ulrichova J, et al. The effectiveness of dried cranberries (Vaccinium macrocarpon) in men with lower urinary tract symptoms. Br J Nutr 2010;104:1181-90.
3. Bailey DT, Dalton C, Joseph Daugherty FJ, Tempesta MS. Can a concentrated cranberry extract prevent recurrent urinary tract infections in women? A pilot study. Phytomedicine 2007;14:237-41.
4. Salo J, Uhari M, Helminen M, et al. Cranberry juice for the prevention of recurrences of urinary tract infections in children: a randomized placebo-controlled trial. Clin Infect Dis 2012;54:340-6
5. Avorn J, Monane M, Gurwitz JH, et al. Reduction of bacteriuria and pyuria after ingestion of cranberry juice. JAMA 1994;271:751-4.
6. Dignam R, Ahmed M, Denman S, et al. The effect of cranberry juice on UTI rates in a long term care facility. J Am Geriatr Soc 1997;45:S53.
7. Walker EB, Barney DP, Mickelsen JN, et al. Cranberry concentrate: UTI prophylaxis. J Family Pract 1997;45:167-8 [letter].
8. Nishizaki N, Someya T, Hirano D, et al. Can cranberry juice be a substitute for cefaclor prophylaxis in children with vesicoureteral reflux? Pediatr Int 2009;51:433-4.
9. Sobota AE. Inhibition of bacterial adherence by cranberry juice: Potential use for the treatment of urinary tract infections. J Urol 1984;131:1013-6.
10. Schlager TA, Anderson S, Trudell J, Hendley JO. Effect of cranberry juice on bacteriuria in children with neurogenic bladder receiving intermittent catheterization. J Pediatr 1999;135:698-702.
11. Sobota AE. Inhibition of bacterial adherence by cranberry juice: Potential use for the treatment of urinary tract infections. J Urol 1984;131:1013-6.
12. 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.
13. 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.
14. Avorn J, Monane M, Gurwitz JH, et al. Reduction of bacteriuria and pyuria after ingestion of cranberry juice. JAMA 1994;271:751-4.
15. Walker EB, Barney DP, Mickelsen JN, et al. Cranberry concentrate: UTI prophylaxis. J Family Pract 1997;45:167-8 [letter].
16. Leaver RB. Cranberry juice. Prof Nurse 1996;11:525-6 [review].
17. Schlager TA, Anderson S, Trudell J, Hendley JO. Effect of cranberry juice on bacteriuria in children with neurogenic bladder receiving intermittent catheterization. J Pediatr 1999;135:698-702.
18. Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima Publishing, 1996, 57-61.
19. Saltzman JR, Kemp JA, Golner BB, et al. Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B12 absorption. J Am Coll Nutr 1994;13:584-91.
20. Saltzman JR, Kemp JA, Golner BB, et al. Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B12 absorption. J Am Coll Nutr 1994;13:584-91.
21. No authors listed. Possible interaction between warfarin and cranberry juice. Curr Prob Pharmacovigilance 2003;29:8.
22. Terris MK, Issa MM, Tacker JR. Dietary supplementation with cranberry concentrate tablets may increase the risk of nephrolithiasis. Urology 2001;57:26-9.
Last Review: 07-08-2014
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