Be aware that the U. S. Food and Drug Administration does not strictly
regulate herbs and dietary supplements. There is no guarantee of strength,
purity or safety of products containing or claiming to contain valerian.
Decisions to use herbs or supplements should be carefully considered. Individuals
using prescription drugs should discuss taking herbs or supplements with
their pharmacists or health care providers before starting.
Scientists have studied cranberry for the following health problems:
Urinary tract infection prevention
Multiple studies report that taking cranberry juice or pills by mouth may
help prevent urinary tract infections and may particularly work against the
bacteria Escherichia coli. Side effects are common in human trials.
A recent meta-analysis concludes that there is some evidence from two
good-quality randomized clinical trials that cranberry juice may decrease
the number of symptomatic urinary tract infections over a 12-month period
in women. If it is effective for other groups such as children and elderly
men and women is not clear. The large number of dropouts/withdrawals from
some of the trials indicates that cranberry juice may not be acceptable over
long periods of time. In addition, it is not clear what is the optimum dosage
or method of administration (for example, juice or tablets). Further properly
designed trials with relevant outcomes are needed.
Urinary tract infection treatment
Studies have found that cranberry is not helpful for treating urinary tract
infections once they have already started. It may be used as an adjunct to
conventional therapy. With the emergence of antibiotic resistant organisms,
alternative antibiotic treatment is being sought out. Cranberry is a
phytomedicine that has been proven effective for urinary tract infections
and may prove as a promising alternative.
Cranberry has been studied for several other purposes, but without enough
scientific evidence to make any recommendations. These areas of study include
prevention of Helicobacter pylori infections (which may occur in the
stomach or early part of the intestine and may cause ulcers), viral or fungal
infections, kidney stones, dental plaque, cancer, urine acidification, care
of urostomy sites and reduction of odor from urinary incontinence.
Early research suggests cranberry juice is not an effective treatment in
the prevention of urinary tract infections caused by neurogenic bladder or
in the treatment of urinary symptoms from prostate cancer radiation therapy.
Cranberry has been suggested for many other uses, based on tradition or
on scientific theories. However, these uses have not been thoroughly studied
in humans, and there is limited scientific evidence about safety or
effectiveness. Some of these suggested uses are for conditions that are
potentially serious and even life-threatening. You should consult a health
care provider before using cranberry for any unproven use.
Antifungal, Candida albicans
Chronic urinary tract infections
Decontamination of meats
|Improved brain function
Vitamin B-12 absorption
Individuals with allergies to plants of the Vaccinium species (cranberries
and blueberries) are more likely to have allergic reactions to cranberry
Few side effects have been reported with cranberry when used at the recommended
doses. At higher doses, the most common complaints include stomach discomfort
and diarrhea. Cranberry should not be used instead of antibiotics for the
treatment of urinary tract infections. Some experts recommend limiting the
use of cranberry by people with certain types of kidney stones. Individuals
with diabetes should drink sugar-free cranberry juice to avoid excessive
sugar intake. One study showed the occurrence of vaginal yeast infections
in women who consume cranberry juice.
Pregnancy And Breast-Feeding
Cranberry cannot be recommended during pregnancy or breast-feeding in amounts
greater than usually found in foods. Many experts believe that cranberry
is safe, but currently there is not enough information. Be aware that many
tinctures contain high levels of alcohol and should be avoided during pregnancy.
Interactions with drugs, supplements and other herbs have not been thoroughly
studied. The interactions listed below have been reported in scientific
publications. If you are taking prescription drugs, speak with your health
care provider or pharmacist before using herbs or dietary supplements.
Interactions With Drugs
Cranberry can increase vitamin B-12 absorption in people taking proton-pump
inhibitors, such as esomeprazole (Nexium). Because of its acidity, cranberry
juice may, in theory, increase the effects of antibiotics, affect how the
kidneys remove certain drugs from the body and counteract antacids. The high
alcohol content in some cranberry tinctures may lead to vomiting if used
with the drug disulfiram (Antabuse) or metronidazole (Flagyl).
Studies have shown that taking the prescription blood thinner warfarin and
cranberry products at the same time can elevate the international normalized
ratio for anticoagulant monitoring, which could increase the risk of bleeding.
Interactions With Herbs And Dietary Supplements
In theory, cranberry juice may affect how the kidneys remove certain herbs
and dietary supplements from the body. Theoretically, cranberry products
may increase the risk of bleeding in people taking other herbs or supplements
like garlic or danshen. Check with your health care provider before using
other herbs and dietary supplements with cranberry.
The doses listed below are based on scientific research, publications
or traditional use. Because most herbs and supplements have not been thoroughly
studied or monitored, safety and effectiveness may not have been proven.
Brands may be made differently, with variable ingredients even within the
same brand. Combination products often contain small amounts of each ingredient
and may not be effective. Appropriate dosing should be discussed with a health
care provider before starting therapy; always read the recommendations on
a product's label. The dosing for unproven uses should be approached cautiously,
because scientific information is limited in these areas.
For Urinary Tract Infection Prevention
Adults (Aged 18 Or Older)
Cranberry juice cocktail (sweetened): A dose of 300 milliliters (10
ounces) per day by mouth has been used.
100 Percent cranberry juice (unsweetened): A dose of 15 to 30 milliliters
per day has been taken by mouth. One study suggests that 500 milliliters
of cranberry juice with 1,500 milliliters of water is sufficient in helping
prevent the formation of oxalate kidney stones.
Capsules (of cranberry juice powder): Between one and six 300- to
400-milligram capsules twice daily by mouth have been taken with water one
hour before or two hours after meals.
Frozen juice concentrate: A dose of 1.5 ounces twice daily has been
Tincture: A dose of four to five milliliters three times daily has
been by mouth.
Children (Younger Than 18): The dosing and safety of cranberry
have not been studied thoroughly in children, and it is recommended that
you discuss doses with your child's health care provider before starting
therapy. The amount of cranberry usually found in foods is often assumed
to be safe. One study used doses of 300 milliliters of cranberry juice daily
for three months in children aged 2 to 18 years; however, there is not enough
scientific support or safety data for this dosage.
Although cranberry has been suggested for many conditions, the best evidence
supports its use for preventing urinary tract infections. Cranberry has not
been proven effective for any other health conditions. People taking proton-pump
inhibitors, antacids, antibiotics and drugs removed from the body by the
kidneys should consult their health care provider before taking cranberry
in amounts greater than usually found in foods. People with diabetes should
be aware that cranberry juice may be high in sugar; sugar-free cranberry
juice products are available. Remember that tinctures may contain large amounts
of alcohol and may cause nausea and vomiting if taken with the drug disulfiram
or metronidazole. Consult your health care provider if you experience side
The information in this monograph was prepared by the professional staff
at Natural Standard, based on thorough systematic review of scientific evidence.
The material was reviewed by the Faculty of the Harvard Medical School with
final editing approved by Natural Standard.
Standard: An organization that produces scientifically based reviews
of complementary and alternative medicine (CAM) topics
for Complementary and Alternative Medicine (NCCAM): A division of the
U.S. Department of Health & Human Services dedicated to research
Selected Scientific Studies: Cranberry
Natural Standard reviewed more than 220 articles to prepare the professional
monograph from which this version was created.
Some of the more recent studies are listed below:
Burger O, Ofek I, Tabak M, et al. A high molecular mass constituent of cranberry
juice inhibits helicobacter pylori adhesion to human gastric mucus. FEMS
Immunol Med Microbiol 2000;29(4):295-301.
Campbell G, Pickles T, D'yachkova Y. A randomised trial of cranberry versus
apple juice in the management of urinary symptoms during external beam radiation
therapy for prostate cancer. Clin Oncol (R Coll Radiol) 2003;Sep, 15(6):322-328.
Carson CF, Riley TV. Non-antibiotic therapies for infectious diseases. Commun
Dis Intell 2003;27(Suppl):S143-S146.
Cavanagh HM, Hipwell M, Wilkinson JM. Antibacterial activity of berry fruits
used for culinary purposes. J Med Food 2003;Spring, 6(1):57-61.
Chambers BK, Camire ME. Can cranberry supplementation benefit adults with
type 2 diabetes? Diabetes Care 2003;Sep, 26(9):2695-2696.
Dignam R, Ahmed M, Denman S, et al. The effect of cranberry juice on UTI
rates in a long term care facility. The Journal of the American Geriatrics
Ebringer A, Rashid T, Wilson C. Rheumatoid arthritis: proposal for the use
of anti-microbial therapy in early cases. Scand J Rheumatol 2003;32(1):2-11.
Grant P. Warfarin and cranberry juice: an interaction? J Heart Valve Dis
Greenberg JA, Newman SJ, Morgan MA. Cranberries and urinary-tract health:
a knowledge assessment of American College of Obstetricians and Gynecologists
fellows. J Altern Complement Med 2004;Aug, 10(4):603-605.
Jepson RG, Mihaljevic L, Craig J. Cranberries for preventing urinary tract
infections. Cochrane Database Syst Rev 2000;(2):CD001321.
Kontiokari T, Sundqvist K, Nuutinen M, et al. Randomised trial of
cranberry-lingonberry juice and Lactobacillus GG drink for the prevention
of urinary tract infections in women. BMJ 2001;322(7302):1571-1573.
Lee YL, Owens J, Thrupp L, et al. Does cranberry juice have antibacterial
activity? JAMA 2000;283(13):1691.
Linsenmeyer TA, Harrison B, Oakley A, et al. Evaluation of cranberry supplement
for reduction of urinary tract infections in individuals with neurogenic
bladders secondary to spinal cord injury: a prospective, double-blinded,
placebo-controlled, crossover study. J Spinal Cord Med 2004;27(1):29-34.
Lynch DM. Cranberry for prevention of urinary tract infections. Am Fam Physician
2004;Dec 1, 70(11):2175-2177. Review.
McHarg T, Rodgers A, Charlton K. Influence of cranberry juice on the urinary
risk factors for calcium oxalate kidney stone formation. BJU Int 2003;Nov,
Patel DA, Gillespie B, Sobel JD, et al. Risk factors for recurrent vulvovaginal
candidiasis in women receiving maintenance antifungal therapy: results of
a prospective cohort study. Am J Obstet Gynecol 2004;Mar, 190(3):644-653.
Pedersen CB, Kyle J, Jenkinson AM, et al. Effects of blueberry and cranberry
juice consumption on the plasma antioxidant capacity of healthy female
volunteers. Eur J Clin Nutr 2000;54(5):405-408.
Schlager TA, Anderson S, Trudell J, et al. Effect of cranberry juice on
bacteriuria in children with neurogenic bladder receiving intermittent
catheterization. J Pediatr 1999;135(6):698-702.
Terris MK, Issa MM, Tacker JR. Dietary supplementation with cranberry concentrate
tablets may increase the risk of nephrolithiasis. Urology 2001;57(1):26-29.
Waites KB, Canupp KC, Armstrong S, DeVivo MJ. Effect of cranberry extract
on bacteriuria and pyuria in persons with neurogenic bladder secondary to
spinal cord injury. J Spinal Cord Med 2004;27(1):35-40.
Wechsler A. Recurrent cystitis in non-pregnant women. Clin Evid
2003;Dec(10):2210-2218. Review. available.
Last updated June 02, 2005