What Is It?
Health Benefits

Dosage Information

Guidelines for Use

General Interaction

Possible Side Effects



Evidence Based Rating Scale


What Is It?

Generations of American women have known that the bitter native cranberry is more than just the basis of a Thanksgiving relish. In fact, these small, dark red berries have a long medical history in addition to a colorful culinary one. Specifically, cranberry juice and cranberry Extract appear to help prevent urinary tract infections in susceptible populations. Most women develop this type of problem at least once in their lives, and some suffer from all too frequent recurrences.

The name "cranberry" evolved from "craneberry" (a common name for the low growing shrub Vaccinum macrocarpon) because the plant’s flowers resemble the heads of cranes frequently spotted in the bogs where cranberries thrive. Cranberries contain almost 90% water. Other constituents in cranberries include quercetin, ascorbic acid, citric acids, some sugars, and polyphenols (tannins). A polyphenol fraction known as the nondialyzable material (NDM), obtained by dialysis of concentrated cranberry juice, contains about 65% proanthocyanidins that, in the laboratory, inhibit adhesion of the bacteria E. coli to the cells lining the urinary tract. (15) This property may contribute to several other benefits as well.

Health Benefits

Early American physicians successfully applied crushed cranberries to tumors and wounds. They also used cranberries as a remedy for the age-old malady known as Scurvy, a disease caused by a deficiency of Vitamin C. (1) Thus, it wasn’t  surprising when modern scientists discovered that cranberries contain plentiful stores of this common Antioxidant vitamin.

A 2010 review of scientific evidence suggests the polyphenols in cranberry juice show promise in fighting various plaque-forming bacteria associated with gingivitis and gum disease. These polyphenols may reduce inflammation and interfere with the adhesion of bacteria to teeth and gums. (1) If using cranberry juice for this purpose is a consideration, however, stick with the natural unsweetened variety. Commercial cranberry juice cocktails are very high in sugar, a gum-disease culprit in its own right.

The polyphenols in cranberry may also be responsible for inhibiting the adhesion of Helicobacter pylori (H. pylori) to the lining of the stomach, thus inhibiting the development of gastric ulcers. In one study, cranberry extract suppressed two different strains of H. pylori. (2)

Laboratory studies additionally indicate cranberry juice may affect the ability of the influenza virus to adhere to host cells. This reduces the infectivity of the virus and suggests cranberry juice may have therapeutic potential in flu prevention. (3)

Researchers have also found that cranberry juice may deodorize urine, a real boon for individuals who suffer from incontinence. (4) In fact, the most popular medicinal uses by far for cranberry relate to urinary tract conditions.

Specifically, cranberry may help to:

Protect against cancer and vascular diseases. Laboratory and animal studies indicate a preventive role for the phytochemicals in cranberries. These phytochemicals may inhibit the growth of certain cancers and vascular diseases including atherosclerosis and ischemic stroke. (5) In a 2008 update of the anticancer activities of cranberry, the authors noted in vitro (laboratory) tumor models show cranberry inhibits the growth of several types of cancer cells including breast, colon, lung, and prostate. (6) In a placebo-controlled study, cranberry juice concentrate was administered to rats in various doses for six months following exposure to a bladder cancer-inducing agent. At the end of the study, the group of rats given cranberry juice had 38% fewer bladder tumors than the control group. In addition, cranberry juice did not cause weight gain or any toxicity. The results suggest a basis for further studies in humans. (7)

Manage hyperglycemia. Laboratory studies of two cranberry powders indicate the phenolics in cranberry inhibit the enzymes responsible for hyperglycemia, or high blood sugar. These results suggest cranberry may potentially help in the management of diabetes; however, studies are needed in animals and humans using standardized extracts before cranberry can be recommended for this use. (8)

Prevent and relieve symptoms of urinary tract infections (UTIs). Over the decades, countless women have used pure cranberry juice or cranberry juice cocktail to self-treat their UTIs. This common infection typically causes a burning sensation while urinating as well as a frequent and often intense urge to do so. For a long time, cranberries were thought to directly fight the infection by acidifying the urine to such an extent that bacteria such as Escherichia coli would languish or die. In fact, while cranberries are acidic, they do not acidify urine as previously believed. Today, the prevailing theory is that cranberry juice inhibits microorganisms from adhering to the mucosal cells lining the urinary tract, making it more difficult for them to proliferate and more likely that they will be eliminated with urination.  

Several clinical trials now corroborate that this folk remedy may have a preventive benefit in some populations. In a 2009 study, 84 girls between the ages of 3 and 14 were given either placebo, 50mL of cranberry juice daily, or Lactobacillus for five days out of the month. After six months, the girls who drank the cranberry juice had the lowest incidence of recurring UTIs. The results suggest daily consumption of concentrated cranberry juice can significantly prevent the recurrence of UTIs in children. Larger studies are needed to confirm these results. (9)

Another group that may benefit from a cranberry product is elderly men with lower urinary tract symptoms (LUTS) associated with prostate disease. In a recent study, 42 men with LUTS, elevated prostate-specific antigen (PSA), negative prostate biopsy, and clinically confirmed non-bacterial prostatitis (inflamed prostate) were given either 1500mg of dried powdered cranberries or placebo daily for six months. At the end of the study, the men who received cranberry powder had significant improvements in the International Prostate Symptom Score and urinary parameters, and they had lower total PSA levels. Cranberry may alleviate LUTS in this population, but larger studies are needed. (10)

A study of 188 pregnant women was done to determine the effects of daily cranberry juice in preventing asymptomatic bacteruria (a precursor to more serious UTIs in pregnant women). The women were given cranberry juice three times a day, cranberry juice once a day, or placebo. At the end of the study, consumption of cranberry juice appeared to have a protective effect in pregnant women. However, 73 participants (39%) withdrew from the study mainly due to gastrointestinal upset. (11)

Cranberry juice doesn’t work for everyone. In a study of 319 college-age women with acute UTIs, the women were given either cranberry juice or placebo and followed for six months or until their next UTI, whichever came first. The results indicated that drinking 8 ounces of 27% cranberry juice twice a day did not decrease the 6-month incidence of a recurrent UTI compared to placebo in college-age women. (12)  And a 2008 Cochrane review suggested that cranberry does not prevent UTIs in people with indwelling urinary catheters. (13) In general, this herbal remedy is better taken to prevent recurrent UTIs than to treat a potentially serious infection that has already developed.

Reduce the risk of kidney stones. The results of a 2003 study of 20 healthy young men with no history of kidney stones indicated that daily consumption of 500mL of 30% cranberry juice with 1500mL of water for two weeks significantly altered three urinary risk factors for kidney stones. Calcium oxalate, uric acid and calcium phosphate levels were all at levels suggesting a lower risk of kidney stones compared to those drinking 2000mL of water alone. (14) Additionally, anecdotal reports indicate that cranberry may help to reduce the risk of infection in the presence of urinary stones and "bladder gravel."


  • fresh berry
  • liquid juice
  • concentrated juice
  • tablet
  • dried herb
  • powdered herb
  • capsule
  • purified proanthocyanidin

Dosage Information

Special tips:

  • Be aware that many major brands of cranberry juice cocktail are only 30% cranberry juice, with water and sweeteners making up the difference. For a smaller amount of juice, try a high-quality, full-strength cranberry juice product, often sold at health-food stores. Add apple juice, if the taste is too tart.

  • A cup of cooked fresh cranberries is roughly equivalent to a 400 mg cranberry capsule, but the tangy flavor may require the addition of a sweetener.     

To prevent UTIs: Drink three or more fluid ounces of cranberry juice cocktail (containing at least 30% juice) daily. Alternatively, take four to six 500 mg capsules of dried cranberry powder; the total milligram dosage should be at least 2,000 mg daily.

Guidelines for Use

 Drinking lots of water or other fluids, in addition to taking cranberry, will speed recovery from a UTI.        

General Interaction

Anyone using medication that affects the kidneys or urinary tract should consult a doctor before using cranberry.

Possible Side Effects

 Drinking cranberry juice in large quantities can cause diarrhea and stomach upset.

 No serious side effects have been associated with the use of moderate amounts of cranberry in supplement form. However, some people develop loose stools as a result of treatment with cranberry supplements: stop taking them or reduce dose if this occurs.


 Anyone with symptoms suggestive of a UTI (painful and frequent urination) should consult a doctor. Antibiotics may be necessary to prevent serious complications.

 Keep in mind that cranberry products may not eliminate or wash away all bacteria, which is why prescription Antibiotic treatment may be needed to knock out a UTI completely. Without appropriate treatment, persistent or recurrent infections might cause infections in the upper urinary tract that may be harmful to the kidneys. Signs and symptoms of this potentially serious complication include mid back (flank) pain, fever, chills, and possibly blood in the urine. Seek professional care.


1. Bonifait L, Grenier D. Cranberry polyphenols: potential benefits for dental caries and periodontal disease. J Can Dent Assoc. 2010;76:a130.
2. Matsushima M, Suzuki T, Masui A, Kasai K, Kouchi T, Takagi A, Shirai T, Mine T. Growth inhibitory action of cranberry on Helicobacter pylori. J Gastroenterol Hepatol. 2008 Dec;23 Suppl 2:S175-80.
3. Weiss EI, Houri-Haddad Y, Greenbaum E, Hochman N, Ofek I, Zakay-Rones Z. Cranberry juice constituents affect influenza virus adhesion and infectivity. Antiviral Res. 2005 Apr;66(1):9-12.
4. Harkins KJ. What's the use of cranberry juice? Age Ageing. 2000 Jan;29(1):9-12.
5. Neto CC. Cranberry and blueberry: evidence for protective effects against cancer and vascular diseases. Mol Nutr Food Res. 2007 Jun;51(6):652-64.
6. Neto CC, Amoroso JW, Liberty AM. Anticancer activities of cranberry phytochemicals: an update. Mol Nutr Food Res. 2008 Jun;52 Suppl 1:S18-27.
7. Prasain JK, Jones K, Moore R, Barnes S, Leahy M, Roderick R, Juliana MM, Grubbs CJ. Effect of cranberry juice concentrate on chemically-induced urinary bladder cancers. Oncol Rep. 2008 Jun;19(6):1565-70.
8. Pinto Mda S, Ghaedian R, Shinde R, Shetty K. Potential of cranberry powder for management of hyperglycemia using in vitro models. J Med Food. 2010 Oct;13(5):1036-44.
9. Ferrara P, Romaniello L, Vitelli O, Gatto A, Serva M, Cataldi L. Cranberry juice for the prevention of recurrent urinary tract infections: a randomized controlled trial in children. Scand J Urol Nephrol. 2009;43(5):369-72.
10. Vidlar A, Vostalova J, Ulrichova J, Student V, Stejskal D, Reichenbach R, Vrbkova J, Ruzicka F, Simanek V. The effectiveness of dried cranberries ( Vaccinium macrocarpon) in men with lower urinary tract symptoms. Br J Nutr. 2010 Oct;104(8):1181-9. Epub 2010 Aug 31.
11. Wing DA, Rumney PJ, Preslicka CW, Chung JH. Daily cranberry juice for the prevention of asymptomatic bacteriuria in pregnancy: a randomized, controlled pilot study. J Urol. 2008 Oct;180(4):1367-72.
12. Barbosa-Cesnik C, Brown MB, Buxton M, Zhang L, DeBusscher J, Foxman B. Cranberry juice fails to prevent recurrent urinary tract infection: results from a randomized placebo-controlled trial. Clin Infect Dis. 2011 Jan;52(1):23-30.
13. Jepson RG, Craig JC. Cranberries for preventing urinary tract infections. Cochrane Database Syst Rev 2008;(1):CD001321.
14. 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;92(7):765-8.
15. Howell AB, Reed JD, Kreuger CG, Winterbottom R, Cunningham DG, Leahy M. A-type cranberry proanthocyanidins and uropathogenic bacterial anti-adhesion activity. Phytochemistry. @005;66(18):2281-91.

Evidence Based Rating Scale

The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies and what our clinical advisors have found to be efficacious in their personal practice into a visual and easy to interpret format. This tool is meant to simplify the information on supplements and therapies that demonstrate promise in the treatment of certain conditions.






Preliminary laboratory studies suggest cranberry may help manage hyperglycemia; additional studies are needed in animals and humans. Avoid use of sugar containing products. (7)

Kidney Stones  
One small study suggests protection against kidney stone formation. (14)
Urinary bladder cancer  
Animal studies indicate reduced incidence of urinary bladder cancer; human studies needed. (8)

Urinary tract infections (UTIs),  
Studies indicate preventive effect in children, elderly men, and pregnant women. Larger studies are needed to recommend for all groups (9-13)

Date Published: 04/18/2005
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