Cranberry (Vaccinium macrocarpon) has been used as both food and medicine for centuries. It is native to North America and was used by Native Americans to treat bladder and kidney diseases. Early settlers from England learned to use the berry both raw and cooked for many conditions, including appetite loss, stomach problems, blood disorders, and scurvy, caused by not getting enough vitamin C.
Cranberry is best known for preventing urinary tract infections (UTIs), commonly caused by bacteria known as Escherichia coli (E. coli). At first, doctors thought cranberry worked by making urine acidic enough to kill the bacteria. Now, studies show that cranberry may prevent bacteria from attaching to the walls of the urinary tract. Good scientific studies support using cranberry, either in capsules or as juice, for preventing -- though not treating -- UTIs.
Found primarily in North America and grown in bogs, cranberry is an evergreen shrub related to blueberry, buckberry, huckleberry, and bilberry. The cranberry bush has upright branches with leaves that are speckled underneath by tiny dots. Pink flowers blossom and red-black fruits appear during June and July.
Cranberry fruit is high in antioxidants, partly from substances called proanthocyanidins, which give cranberries their vibrant color. Antioxidants neutralize particles in the body known as free radicals, which damage DNA and are throught to contribute to heart disease, diabetes, cancer and other conditions.
Cranberries are also an excellent source of vitamin C, another important antioxidant. Scientists are researching to see if the antioxidants in cranberries will help protect against heart disease and cancer.
The ripe fruit of the cranberry is the part used as food and medicine.
Medicinal Uses and Indications
Urinary tract infections
Several studies indicate that cranberry helps prevent UTIs of the bladder and urethra (the tube that drains urine from the bladder), especially for women who have frequent UTIs. In one study of older women, cranberry juice reduced the amount of bacteria in the bladder compared to placebo. Another study showed that younger women with a history of frequent UTIs who took cranberry capsules had fewer UTIs compared to those who took placebo.
However, studies suggest that cranberry doesn't work once you have a UTI. That's because it helps keep bacteria from attaching to the urinary tract, but it's less effective once the bacteria have already attached. That's why cranberry is better at preventing UTIs than treating them. UTIs should be treated with conventional antibiotics.
Two studies that cranberry may also prevent the bacteria Helicobacter pylori from attaching to stomach walls. H. pylori can cause stomach ulcers, so cranberries may play a role in the preventing stomach ulcers. More research is needed to be sure cranberry helps.
Cranberry is also being studied for the following conditions, although there isn't enough evidence yet to tell whether it helps prevent or treat them:
Cancer -- Some test tube and animal studies suggest cranberry may help stop cancer cells from growing.
High cholesterol -- One preliminary study found that drinking cranberry juice raised HDL "good" cholesterol levels.
Viruses -- Cranberry seems to fight some viruses in test tubes. Studies in people are needed.
You can get cranberries fresh or frozen and in juice and concentrate forms. Dried berries are also available as tablets or capsules. Pure cranberry juice is very sour, so most juices contain a mixture of cranberries, sweeteners -- which may make the juice less healthy -- and vitamin C. Look for a brand of cranberry juice that has the lowest amount of added sugar or is sugar-free.
How to Take It
Cranberry juice is considered safe for children to drink. However, there is not enough evidence to say what would be a safe dose for children prone to UTIs. A child with a UTI should be seen by a doctor.
- Juice: Studies have used 3 or more fluid oz. of pure juice per day, or about 10 oz. of cranberry juice cocktail, for preventing UTIs. Ask your doctor about the right dose for you.
- Fresh or frozen cranberries: 1.5 ounces
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, can trigger side effects and can interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider.
Cranberry juice is generally considered safe with no serious side effects, even for pregnant women. Cranberry supplements are considered safe for most people, although pregnant and breastfeeding women should ask their doctor before taking any supplement, including cranberry.
Cranberry has relatively high levels of oxalate, chemicals that may raise the risk of kidney stones in some people. If you have kidney stones, talk to your doctor before taking cranberry supplements or drinking a lot of cranberry juice.
Don’t use cranberry if you already have a UTI. You should see a doctor for prescription antibiotics.
Most cranberry juice has added sugar. People who have diabetes should look for brands that are artificially sweetened or should be careful how much sweetened juice they drink.
People who are allergic to aspirin may also be allergic to cranberry.
Warfarin (Coumadin) -- Cranberry may raise the risk of bleeding, especially if you already take medications to thin the blood such as warfarin. The evidence is mixed and not completely clear, so it’s best to ask your doctor before you take cranberry or drink a lot of juice.
Aspirin -- Like aspirin, cranberries contain salicylic acid. If you take aspirin regularly -- as a blood-thinner, for example -- or if you are allergic to aspirin, you should not take cranberry supplements or drink a lot of juice.
Other medications -- Cranberry may interact with medications that are broken down by the liver. To be safe, if you take any medications, ask your doctor before taking cranberry.
Ahuja S, Kaack B, Roberts J. Loss of fimbrial adhesion with the addition of Vaccinum macrocarpon to the growth medium of P-fimbriated Escherichia coli. J Urol. 1998;159:559-562.
Aston JL, Lodolce AE, Shapiro NL. Interaction between warfarin and cranberry juice. Pharmacotherapy. 2006 Sep;26(9):1314-9.
Avorn J, Monane M, Gurwitz JH, Glynn RJ, Choodnovskiy I, Lipsitz LA. Reduction of bacteriuria and pyuria after ingestion of cranberry juice. JAMA. 1994;271:751-754.
Bailey DT, Dalton C, Joseph Daugherty F, et al. Can a concentrated cranberry extract prevent recurrent urinary tract infections in women? A pilot study. Phytomedicine. 2007 Feb 10; [Epub ahead of print].
Bomser J, Madhavi DL, Singletary K, et al. In vitro anticancer activity of fruit extracts from Vaccinium species. Planta Med. 1996;62(3):212-216.
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 Dec;29(4):295-301.
Caton PW, Pothecary MR, Lees DM, Khan NQ, Wood EG, Shoji T, Kanda T, Rull G, Corder R. Regulation of vascular endothelial function by procyanidin-rich foods and beverages. J Agric Food Chem. 2010 Apr 14;58(7):4008-13.
Côté J, Caillet S, Doyon G, Sylvain JF, Lacroix M. Analyzing cranberry bioactive compounds. Crit Rev Food Sci Nutr. 2010 Oct;50(9):872-88.
Dugoua JJ, Seely D, Perri D, Mills E, Koren G. Safety and efficacy of cranberry (vaccinium macrocarpon) during pregnancy and lactation. Can J Clin Pharmacol. 2008;15(1):e80-6.
Duthie SJ, Jenkinson AM, Crozier A, et al. The effects of cranberry juice consumption on antioxidant status and biomarkers relating to heart disease and cancer in healthy human volunteers. Eur J Nutr. 2006 Mar;45(2):113-22. Epub 2005 Jul 20.
Howell AB, Vorsa N, Der Marderosian A, et al. Inhibition of the adherence of P-fimbriated Escherichia coli to uroepithelial-cell surfaces by proanthocyanidin extracts from cranberries. N Engl J Med. 1998;339(15):1085-1086.
Jepson RG, Craig JC. Cranberries for preventing urinary tract infections. Cochrane Database Syst Rev. 2008;1: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. 2002;322:1571-1573.
McKay DL, Blumberg JB. Cranberries (Vaccinium macrocarpon) and cardiovascular disease risk factors. Nutr Rev. 2007;65(11):490-502.
Paeng CH, Sprague M, Jackevicius CA. Interaction between warfarin and cranberry juice. Clin Ther. 2007;29(8):1730-5.
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.
Prasain JK. Effect of cranberry juice concentrate on chemically-induced urinary bladder cancers. Oncol Rep. 2008;19(6)1565-70.
Rossi R, Porta S, Canovi B. Overview on cranberry and urinary tract infections in females. J Clin Gastroenterol. 2010 Sep;44 Suppl 1:S61-2. Review.
Ruel G, Pomerleau S, Couture P, Lemieux S, Lamarche B, Couillard C. Low-calorie cranberry juice supplementation reduces plasma oxidized LDL and cell adhesion molecule concentrations in men. Brit J Nutr. 2008;99(2):352-9.
Schlager TA. Effect of cranberry juice on bacteriuria in children with neurogenic bladder. J Pediatr. 1999;135:698-702.
Shmuely H, Yahav J, Samra Z, et al. Effect of cranberry juice on eradication of Helicobacter pylori in patients treated with antibiotics and a proton pump inhibitor. Mol Nutr Food Res. 2007 Jun;51(6):746-51.
Terris MK, Issa MM, Tacker JR. Dietary supplementation with cranberry tablets may increase the risk of nephrolithiasis. Urol. 2001;57:26-29.
Weiss EI, Lev-Dor R, Kashamn Y, et al. Inhibiting interspecies coaggregation of plaque bacteria with a cranberry juice constituent. J Am Dent Assoc. 1998;129(12):1719-1723.
Zhang L, Ma J, Pan K, et al. Efficacy of cranberry juice on Helicobacter pylori infection: a double-blind, randomized placebo-controlled trial. Helicobacter. 2005 Apr;10(2):139-45.
- Last Reviewed on 01/02/2011
- Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2013 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
This page was last updated: May 7, 2013