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Cranberry Juice: Its Effectiveness in Prevention of Urinary Tract Infections

By Jade Morales

October 24, 2008


According to the National Institute of Diabetes and Digestive Kidney Disease (NIDDK), the second most common type of infection in the body is a urinary tract infection. They are responsible for approximately 8.3 million doctors visits each year. Urinary tract infections can affect both sexes, young and old. However, women are more prone to UTIís than men. Although the numbers fluctuate, analysts presume that about 50% percent of women have had at least one urinary tract infection (UTI) in their lifetime. The numbers are smaller, but equally significant for men. Recommended as a remedy for this ailment, isnít a complex pill full of unpronounceable chemicals but a simple juice: Juice from cranberry that is. The healing benefits of cranberry juice arenít something new. Healthcare providers have been recommending cranberry juice as a common aid in ďcuringĒ UTIís for the longest time, even though it isnít an official regimen for the infection. However, the most effective components of cranberry juice that work specifically to prevent urinary tract infections have been an enigma until now.


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What is a Urinary Tract Infection?


A urinary tract infection involves an infection of any organisms that are along the urinary tract. This includes the bladder, kidney, urethra and ureters. However, most UTIís affect the bladder and the urethra. When one or more of the organisms is infected, symptoms may or may not occur. When symptoms do occur, they are usually in the form of a persistent burning sensation, a frequent urge to urinate, strong-smelling urine, and bloody urine among others. Depending on the exact location of the urinary tract infection, symptoms may also include fever, nausea, back pain, and vomiting.

††††††††††† When bacteria successfully enter the urinary tract via the urethra opening, it thrives and multiplies thus causing inflammation to the wall of the urinary tract. The most notorious bacteria found in urinary tract infections are Escherichia coli (E. coli), although there are two less common infection causing microorganisms, Chlamydia and Mycoplasma. The two most common forms of urinary tract infections are cystitis and urethritis. Cystitis is the infection of the bladder that is most commonly associated with the gastrointestinal bacterium E. coli. Because there is such a close proximity from the anus to the urethra and the opening of the urethra to the bladder, this is the most easily transmitted form. Urethritis is just as easily transmitted (

††††††††††† The most common form of treatment for the urinary tract infections is an antibiotic. Depending on what type of urinary tract infection is contracted and the patientís health history, antibiotics can be administered from 3 days to a couple of weeks in order to get rid of the bacteria. However, there is an increasing prevalence of E. coli bacteria that are antibiotic-resistant and this could force medical researchers to find more drugs to combat these resistant strains. Not only that, but up to 20% of women have recurring infections despite having taken antibiotics So then, if antibiotics may not work as well as they have in the past, where may cranberry juice fall into the medical treatment?



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†Why Cranberry Juice?† Preventative Properties of Cranberry Juice


In the past, cranberry juice has been prescribed as a treatment based on itsí acidic nature. Moreover, cranberry juice contains moderate to high levels of vitamin K, vitamin C, and fiber. Many physicians, nutritionists, and other healthcare providers have recommended cranberry juice as treatment in order to balance the pH environment that is caused by Escherichia Coli and other bacterium causing urinary tract infections. But more recently cranberry juice has been recognized for itsí preventative qualities.

Cranberry juice, that is 100% pure juice of cranberry, has adherence properties that prevent certain bacteria like Escherichia coli from clinging to uroepithelial cells in the urinary tract. The cranberry juice specifically alters the effect of two properties of bacteria that cause urinary tract infections (UTIís). The first property of UTIís that cranberry juice targets is the protein fibers of the bacterial cell wall, known as fimbriae. The high fructose level present in cranberry juice inhibits fimbriae from attaching to the wall of the urinary tract. The second property that cranberry juice attacks is the prevention of adherence of certain phenotypes of† E. Coli. Furthermore, cranberry juice contains tannin compounds, known as proanthocyanidins, which target pathogenic organisms that are urinary tract dwelling agent


The good thing is that data suggests that cranberry juice will not target non-pathogenic organisms, which means that it will not kill off necessary bacteria.


How Does Science Explain the Benefits of Cranberry Juice?


In a review conducted by the Cochrane Review, Craig J.C. and Jepson R.G. (2008) performed a meta-analysis on 10 different studies on the effectiveness of cranberry juice consumption on the prevention of urinary tract infections. They found that they could only gather data from four studies in support of cranberry juice reducing the incidence of UTIís in the subjects tested, due to dropouts and inadequate methodological design. However, of the remaining four studies significant evidence proves the benefit of cranberry juice in preventing UTIís when cranberry juice is taken over a 12-month period. Furthermore, the review concluded that cranberry juice was more effective in preventing UTIís in women that have recurring infections (Craig & Jepson 2008).


Data and Results


Of the 10 studies, 4 randomized controlled studies were assessed for the prevention of urinary tract infections. In one of the randomized control studies, the subjects were given 50ml cranberry juice of 7.5g concentrate (Kontiokari 2001). The subjects in the other study were given 250ml cranberry juice with 1:30 concentrate or the same concentration of cranberry in a tablet form (Stothers 2002). Both of the studies were compared with a controlled or placebo group.† After a comparison of the two different groups in each study, it was found that the relative risk was .61 which means that the group given cranberry juice were less likely to be at risk of having a recurring UTI than the control groups. In a third study mentioned in the same review was the one conducted on elderly men and women (Mcmurdo 2005). His data compared cranberry juice groups with placebo groups. The group with cranberry juice only reported 7 out of 187 individuals developing symptomatic UTI while the placebo group reported 14 out of 189 individuals developing symptomatic UTIs. That means that in this study those that were in the placebo group had twice as many people develop a UTI than those in the cranberry group.


Discussion and Conclusion


The authors of the review explain that many of the studies werenít able to be assessed on itsí effectiveness because of design flaws and the significant withdrawal rate. They suggest that perhaps cranberry juice consumption is hard to test long-term. Despite the problems with the meta-analysis, researchers are able to look at the data of 4 ďgood-qualityĒ studies and focus on 3 significant studiesí findings. The first two studies mentioned, Kontiokari (2001) and Stothers (2002) demonstrate the effectiveness of cranberry juice, either in liquid or tablet form, most significantly on women with a history of urinary tract infections. The third study (McMurdo 2005) demonstrates the effectiveness of cranberry juice due to the fact that there were fewer infections due to E. coli in the cranberry group. The authors of the review could only conclude on 2 of the 10 studies that cranberry juice was effective in preventing UTI. This was due to the flaws in designs and dropouts that render the data untestable.


Is There More Evidence in Favor of Cranberry Juice?


A study conducted by Agniel et. Al 2006 aimed to compare cranberry juice consumption versus a placebo on the anti-adherence ability of in vitro bacteria in the urine of healthy individuals. This particular study may prove to be more convincing mainly because it is testing cranberry juicesí effect on those organisms that cause urinary tract infections.



The subject pool included 10 women and 10 males that were arranged in a random, double blind, crossover study in which the placebo was controlled.



Each of the subjects was randomly assigned to four groups receiving 750ml of a drink. Group 1 received a drink composed of 500ml of water and 250ml of a placebo. Group 2 received 250ml of cranberry juice and 500ml of water. Group 3 received 750ml of the placebo while group 4 received 750ml of cranberry juice. Each subject received each of the four types of regimen in a random order, with a washout period of 6 days or more. After each regimen, 10 to 12 hrs later the urine sample was taken. There were six strains of bacteria that were previously isolated from UTI patients. There was a presence of a gene marker for P-fimbria papC, in order to detect specific strains of E. coli. Antibiotics, such as tetracycline, ofloxacin, and ciprofloxacin were used as zone diameters for resistance. The bacterial adherence experiments were conducted with T24 cells, which are bladder epithelial cells. The bacteria cells were then grown in human urine, and then tested with an adhesion index.



Figure 1. Proanthocyanidine ( tannin compound)




The highest adhesion index was with urine samples from the placebo drink samples.† The lowest adhesion index was with urine samples from the 750ml cranberry juice, with a slightly higher adhesion index of urine samples from the 250ml cranberry juice samples.



Cranberry juice consumption will significantly reduce the chances of bacteria adhering to the walls of cells like T24 cells (bladder epithelial wall tissue)† due to the tannins and fructose binding to the bacteria. This means a reduction in the likelihood of these strains of E. coli (P-fimbriae) of causing urinary tract infections.


†Is Cranberry Juice a ďCureĒ?


The answer to whether cranberry juice is a ďcureĒ or not is complicated. Depending on the age and the sex of the subjects being tested, cranberry juice may be more effective than others in preventing UTIs. Many of the studies that look at the effects of cranberry juice have on women of all ages, both recurring and first-time infections. The conclusion from the majority of studies has been that cranberry juice can significantly reduce the chance of women both with a history and no history of UTI (Bailey 2006). However, when looking at children with certain bladder infections, they are unable to conclude that cranberry juice can reduce the incidence of these urinary tract infections.


How much cranberry juice is recommended?


Other questions that may arise are what is the amount of cranberry juice that should be consumed and for how long should it be consumed. A majority of the studies have had doses ranging 250ml to 750ml, with most of them showing more significant results for the larger doses. But the exact amount and the duration of the cranberry juice regimen can vary. Most of the studies show significant results from 6 months Ė 12months duration of the cranberry regimen. Still there needs to be more empirical research done in order to figure out the right amount.


Is cranberry juice better than the normal treatment for UTI?


Consumers may be curious to know whether cranberry juice works better than antibiotics. There havenít been any true experiments trying to find out whether antibiotics work more effectively in direct comparison to cranberry juice in reducing the amount of bacteria in the urinary tract. An interesting fact is that many strains of bacteria are resistant to the common antibiotics so pharmaceuticals are constantly trying to find drugs that arenít resistant to these drugs. The article linked above gave similar information. However there website is advertising for cranberry juice and seems that they might have a stake in what is published on their site. On another point, the Craig 2008 article gave an analysis of the cost-effectiveness between the two and found that cranberry juice can be significantly more expensive than antibiotics depending on which brand of cranberry juice consumed and for how long. So this might be a reason that cranberry juice taken as a normal regimen, rather than a supplement, could be more expensive and less practical.


What we know works


What research has told us is that there are two components of cranberry juice, both fructose and proanthocyanidins (tannins) that are effective in preventing the adherence of infection causing bacteria to the tissue of the organs of the urinary tract. So we know that cranberry juice canít be detrimental as being a supplement when used along with other forms of treatment such as antibiotics. We also know that it is more effective for women in general, but no studies have shown it to increase the incidence of urinary tract infections in men. Overall, women are most likely to benefit from a moderate intake of cranberry juice daily, mainly due to the findings of anti-adherence properties of the juice. Other reasons are speculative at this point due to the lack of quality studies.†








































††††††††††††††††††††††††††††††††††††††††††††††††††††††† References



Avorn J, Manone M, Gurwitz JH, et al (2004) Reduction of bacteriuria and pyuria after


ingestion of cranberry juice. Journal of the American Medical Association.




Bailey DT, Dalton C, Joseph Daugherty F, et al (2007) Can a concentrated cranberry


extract prevent recurrent urinary tract infections in women? A pilot study.


Phytomedicine Apr;14(4):237-41.



Craig J.C,Jepson R.G., (2008). Cranberries for preventing urinary tract infections.


Cochrane Database of Systematic Reviews 2008, Issue 1. Art. No.: CD001321.


DOI: 10.1002/14651858.CD001321.pub4.



Di Martino P, Agniel R, David K, Templer C, Gaillard JL, Denys P, Botto H. Reduction


of Escherichia coli adherence to uroepithelial cells after consumption of cranberry


juice: a double blind randomized placebo-controlled crossover trial. World J Urol.





Foo, L.Y., Howell A.B., Marderosian, A.D., Vorsa, N (1998). Inhibition of the


Adherence of P-Fimbriated Escherichia coli to Uroepithelial-Cell Surfaces by


Proanthocyanidin Extracts from Cranberries. The New England Journal of


Medicine. 339: 1085-1086.



Kontiokari T, Sundqvist K, Nuutinen M, Pokka T, Koskela M, Uhari M (2001).


Randomised trial of cranberry-lingonberry juice and Lactobacillus GG drink for


the prevention of urinary tract infections in women. BMJ 322(7302):1571-3.


[MEDLINE: 11431298]  



McMurdo ME, Bissett LY, Price RJ, Phillips G, Crombie IK(2005). Does ingestion of

cranberry juice reduce symptomatic urinary tract infections in older people in

hospital. A double-blind, placebo-controlled trial. Age Ageing.34:256-261.

Stothers L (2001) A randomized trial to evaluate effectiveness and cost effectiveness of

naturopathic cranberry products as prophylaxis against urinary tract infection in women. Canadian Journal of Urology 9(3):1558-62.




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