(CNN) Cranberries, cranberry juice and cranberry products are often recommended as a natural way to prevent urinary tract infections, but a new study suggests that this effort may be futile. 
 
 Nursing home residents who took high-potency cranberry capsules did not have fewer episodes of urinary tract infection than those taking a placebo, researchers discovered. 
 
 "Although our study was only in nursing home women, many other studies have been done in other populations, which have not shown a benefit," said Dr. Manisha Juthani-Mehta, lead author of the study, published in the Journal of the American Medical Association 
 
 "For women that enjoy eating cranberry products or drinking cranberry juice, I encourage them to continue doing so," said Juthani-Mehta, an associate professor at the Yale University School of Medicine. But spending money on cranberry capsules with "limited potential benefit" for preventing urinary tract infections "does not seem worthwhile." 
 
 Searching for an alternative treatment 
 
 Urinary tract infections plague women of all ages, and as men age, they too become increasingly susceptible. UTIs, as they are commonly known, occur when bacteria infect the urinary tract. Symptoms include feeling the need to urinate despite having an empty bladder, pain or burning while peeing, frequent urination, low fever and cloudy or bloody urine. 
 
 The body can sometimes flush out an infection on its own, according to the US Centers for Disease Control and Prevention, but an infection may cause discomfort and could spread to the kidneys, becoming serious. 
 
 Among nursing home residents, UTIs are the most commonly diagnosed infection. Still, it's a difficult diagnosis to make since bacteria in the urine can come without symptoms. Research has showed that up to half of all women living in nursing homes test positive for bacteriuria, or bacteria in the urine, even if they don't experience symptoms of an infection. Pyuria (pus) is present in 90% of residents with bacteriuria. 
 
 To treat infections, doctors usually prescribe antibiotics. Yet the germs causing these infections are becoming less susceptible to these drugs, and infections do not always go away easily. 
 
 Alternatively, a common suggestion for those who suffer recurrent UTIs is to drink plenty of cranberry juice. The acidity of the cranberry is believed to change the pH balance of the urinary tract and bladder to keep an infection from developing. Although the origins of this folk remedy are unclear, a scientific study published in 1923 showed that cranberries, and prunes, affect the acidity of urine. 
 
 "One of the first studies that showed that cranberry juice was effective in older women living in nursing homes and assisted-living facilities was published in 1994," Juthani-Mehta said. 
 
 But since then, she said, there have been multiple conflicting studies: Some show that cranberry juice or capsules do prevent infections, but others say they do not. A 2012 review of 24 studies with a total of 4,473 participants found little evidence and concluded that cranberry juice "cannot be recommended for the prevention of UTIs." 
 
 Juthani-Mehta and her colleagues decided to investigate. Though evidence suggested that cranberry products do not prevent urinary tract infections, she and her colleagues questioned whether the appropriate dose of cranberry had been tested. 
 
 "Since cranberry juice is hard for older women to drink (taste, sugar load, volume), capsules at a high dose of the active ingredient were worthwhile to test," Juthani-Mehta wrote in an email. 
 
 She and her colleagues enlisted the help of 185 women residing in various nursing homes, though only 147 women completed the study. About a third (31%) of the women tested positive for bacteriuria plus pyuria in their urine even before the study began. 
 
 The researchers randomly assigned the women to take two cranberry capsules daily, each containing 36 milligrams of the active ingredient proanthocyanidin, or to take a placebo. 
 
 The research team found no difference in the presence of bacteriuria plus pyuria between the cranberry group and the placebo group. They also found no differences in the episodes of UTIs or rates of death among the two groups. 
 
 Some women found it difficult to stick to the routine, and some missed a dose or two as the yearlong study continued, but Juthani-Mehta stands by her results and her opinion that cranberries are ineffective when it comes to UTI prevention. 
 
 Entrenched popular opinion 
 
 "The realistic amount of cranberry juice that can be ingested on a regular basis makes it impractical to recommend, and in addition, well-designed studies don't show a positive preventive effect," agreed Dr. David Soper of the Medical University of South Carolina. 
 
 "For postmenopausal women, topical estrogen in the vagina has shown to decrease the risk of UTI," Soper said, adding that this treatment has minimal absorption and so is safe to use. 
 
 "It is time to move on from cranberries," wrote Dr. Lindsay E. Nicolle of the University of Manitoba in an editorial published with the study. 
 
 Nicolle may be fighting a difficult battle. Cranberries continue to be suggested as an alternative treatment for urinary tract infections in a number of places, from the popular women's website Our Bodies Ourselves to the austere American Congress of Obstetricians and Gynecologists . They also recommend drinking plenty of fluids to flush out bacteria. 
 
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 Noting that recurrent UTIs are distressing as well as costly, Nicolle advices identifying new approaches to preventing and treating these common infections, including "a wiser use of antimicrobial therapy" and "immunologic interventions." 
 
 Nicolle acknowledges that "a person may, of course, choose to use cranberry juice or capsules for whatever reason she or he wishes," but she says she cannot support cranberries. Evidence from this new study, combined with past research, is now "convincing that cranberry products should not be recommended as a medical intervention for the prevention of UTI." 

 FAQ050, May 2015 
 
 Gynecologic Problems 
 
 How do urinary tract infections ( UTIs) develop? 
 
 Female Urinary Tract 
 
 Most urinary tract infections start in the lower urinary tract, which is made up of the urethra and bladder. Bacteria from the bowel live on the skin near the anus or in the vagina. These bacteria can spread and enter the urinary tract through the urethra. If they move up the urethra, they may cause a bladder infection (called cystitis). Bacteria that have infected the bladder may travel to the upper urinary tract, the ureters and the kidneys. An infection of the kidneys is called pyelonephritis. An upper urinary tract infection may cause a more severe illness than a lower urinary tract infection. 
 
 Women are more likely than men to get UTIs because the urethra is shorter in a woman than in a man. In women, the bacteria can reach the bladder more easily. 
 
 What causes UTIs? 
 
 Women’s anatomy makes them prone to getting UTIs after having sex. The opening of the urethra is in front of the vagina. During sex, bacteria near the vagina can get into the urethra from contact with the penis, fingers, or devices. 
 
 Urinary tract infections also tend to occur in women when they begin having sex or have it more often. Using spermicides or a diaphragm also can cause more frequent UTIs. 
 
 Infections also can occur when the bladder does not empty completely. This condition may be caused by 
 
 blockage (a stone) in the ureters, kidneys, or bladder that prevents the flow of urine through the urinary tract 
 
 a narrowed tube (or a kink) in the urinary tract 
 
 problems with the pelvic muscles or nerves 
 
 What other factors increase the risk of getting a UTI? 
 
 You are more likely to get an infection if you 
 
 have had a UTI before 
 
 have had several children 
 
 have diabetes 
 
 are obese 
 
 Menopause also increases the risk of getting a UTI. During menopause, the level of estrogen decreases. This decrease can cause changes in the tissues around the urethra that can lead to a UTI. 
 
 UTIs can occur during pregnancy. If you are pregnant and think you may have a UTI, be sure to tell your health care provider promptly. If untreated, it may cause problems for you and your baby. 
 
 What are the signs of a UTI? 
 
 One sign is a strong urge to urinate that cannot be delayed (urgency). As urine flows, a sharp pain or burning, called dysuria, is felt in the urethra. The urge to urinate then returns minutes later (frequency). Soreness may be felt in the lower abdomen, in the back, or in the sides. 
 
 Other signs may show up in the urine. It may 
 
 have a strong odor 
 
 look cloudy 
 
 sometimes be tinged with blood 
 
 Blood in the urine may be caused by a UTI, but it also may be caused by other problems. Tell your health care provider promptly if you see blood in your urine. 
 
 If the bacteria enter the ureters and spread to the kidneys, symptoms also may include 
 
 back pain 
 
 chills 
 
 fever 
 
 nausea 
 
 vomiting 
 
 If you have any of these symptoms, tell your health care provider right away. Kidney infections are serious. They need to be treated promptly. 
 
 Symptoms linked with a UTI, such as painful urination, can be caused by other problems (such as an infection of the vagina or vulva). Tests may be needed to confirm the diagnosis. Be sure to let your health care provider know if you have any of these symptoms. 
 
 How are UTIs diagnosed? 
 
 Your health care provider may first do a simple test, called urinalysis, to find out whether you have a UTI. For this test, you will be asked to provide a urine sample. This sample will be studied in a lab for the presence of white and red blood cells and bacteria. Normal urine should not have bacteria or blood cells in it. If either of these shows up in the urine, you may have a UTI. 
 
 The urine sample also may be grown in a culture (a substance that promotes the growth of bacteria) to see which bacteria are present. The sample also may be tested with different antibiotics to see which one destroys the bacteria best. This is called a sensitivity test. 
 
 How are UTIs treated? 
 
 Antibiotics are used to treat UTIs. The type, dose, and length of the antibiotic treatment depend on the type of bacteria causing the infection and on your medical history. 
 
 Treatment is usually quick and effective. Most symptoms go away in 1–2 days. Be sure to take all the medication even though your symptoms may go away before you finish your prescription. If you stop treatment early, the infection may still be present or it could come back after a short time. 
 
 For more severe infections, such as a kidney infection, you may need to stay in the hospital. These infections take longer to treat and you may be given medication intravenously (through a tube in a vein). 
 
 What is a recurrent infection? 
 
 If you have more than two UTIs in a year, you have a recurrent infection. The first step in treatment is finding the cause. Factors that increase the risk of recurrent infection are 
 
 frequent sex 
 
 young age at first UTI 
 
 spermicide use 
 
 diaphragm use 
 
 a new sexual partner 
 
 Recurrent infections are treated with antibiotics. A week or two after you finish treatment, a urine test may be done to see if the infection is cured. Changing your birth control method also may be recommended. If you often get UTIs through sexual activity, you may be given an antibiotic to take in single doses after you have sex. 
 
 How can UTIs be prevented? 
 
 There are a number of ways to prevent UTIs: 
 
 After a bowel movement or after urinating, wipe from front to back. 
 
 Wash the skin around the anus and the genital area. 
 
 Avoid using douches, powder, and deodorant sprays. 
 
 Drink plenty of fluids (including water) to flush bacteria out of your urinary system. 
 
 Empty your bladder as soon as you feel the urge or about every 2–3 hours. 
 
 Try to empty your bladder before and after sex. 
 
 Wear underwear with a cotton crotch. 
 
 Unsweetened cranberry juice and cranberry pills may decrease the risk of getting a UTI. The exact amount of juice or pills needed and how long you need to take them to prevent infection are being studied. Treatment with an estrogen cream or pills is being studied as a way to prevent UTIs in women past menopause. 
 
 Glossary 
 
 Antibiotics: Drugs that treat infections. 
 
 Anus: The opening of the rectum on the outside of the body. 
 
 Bladder: A muscular organ in which urine is stored. 
 
 Dysuria: Pain during urination. 
 
 Estrogen: A female hormone produced in the ovaries. 
 
 Kidneys: Two organs that cleanse the blood, removing liquid wastes. 
 
 Menopause: The process in a woman’s life when ovaries stop functioning and menstruation stops. 
 
 Recurrent Infections: Infections that occur more than once, usually within a short time, although they may be spread out over several months. 
 
 Spermicides: Chemicals (creams, gels, foams) that inactivate sperm. 
 
 Ureters: A pair of tubes, each leading from one of the kidneys to the bladder. 
 
 Urethra: A short, narrow tube that carries urine from the bladder out of the body. 
 
 Vagina: A tube-like structure surrounded by muscles leading from the uterus to the outside of the body. 
 
 Vulva: The external female genital area. 

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 The daily ingestion of cranberry products—juice or capsules—has been promoted as a means to prevent recurrent urinary tract infection (UTI) since at least the first half of the last century.1 In that preantibiotic era, acidification of the urine was a recommended treatment for UTI. Initially, cranberry juice was explored as an approach to treating UTI following the observation that it could lower urine pH. This is attributed to formation of hippuric acid through metabolism of the quinic acid present in cranberry juice. Later studies reported that the concentration of hippuric acid in the urine was insufficient for an antibacterial effect unless very large volumes of cranberry juice were ingested. Subsequently, some lectins (proanthocyanidins) present in cranberries as well as blueberries were reported to inhibit binding of the type 1 P-fimbriae of Escherichia coli to uroepithelial cells, preventing bacterial adherence within the urinary tract. This proposed mechanism for a beneficial effect of cranberries has not yet been shown to have a role in human infection.2 Even though many clinical trials evaluating the use of cranberry products for prevention of UTI have been reported, results have been inconsistent and the efficacy, if any, remains unknown after almost 100 years. 
 
 In this issue of JAMA, the report by Juthani-Mehta and colleagues3 adds another study to the extensive list of clinical trials that have evaluated the potential benefit of cranberry products for prevention of UTI. The authors conducted a randomized, double blind clinical trial enrolling 185 elderly women residing in nursing homes to evaluate the effect of cranberry capsules on clinical and microbiologic outcomes. During the 1-year study period, among the 92 women who received cranberry capsules (72 mg total, equivalent to 20 ounces of cranberry juice) compared with the 93 women who received placebo, there was no significant difference in the primary outcome of presence of bacteriuria with pyuria (adjusted rates, 29.1% vs 29.0%; respectively, odds ratio, 1.01; 95% CI, 0.61-1.66; P=.98). Among the secondary outcomes, there were no significant differences in symptomatic UTI (10 vs 12 episodes), mortality (17 vs 16 deaths), hospitalizations (33 vs 50 episodes), or of any other clinically meaningful outcomes for this population. As expected for elderly women residing in long-term care facilities, 31% of the study participants already had bacteriuria and pyuria present at enrollment. Sensitivity analysis suggested, among women without bacteriuria plus pyuria at enrollment, that there were no between-group differences in the presence of bacteriuria plus pyuria over one year. 
 
 Some important strengths of this study include the use of the objective laboratory criteria of bacteriuria plus pyuria as the primary outcome, and of restrictive clinical criteria requiring localizing genitourinary findings for identification of symptomatic UTI,4 the most important secondary outcome. The clinical ascertainment of symptomatic UTI in elderly women residing in long-term care facilities can be problematic. The very high prevalence of bacteriuria in this population means that the urine culture, while necessary for diagnosis, has no specificity for identification of symptomatic infection. In addition, symptomatic infection is often inappropriately diagnosed through attribution of nonlocalizing nonspecific symptoms—such as increased confusion, fatigue, or falls—to UTI in patients in whom a high prevalence of bacteriuria always exists. Previous studies in this population have often been compromised by inadequate description of clinical criteria for diagnosis of symptomatic infection or when a high proportion of symptomatic episodes are identified based on nonspecific symptoms. The current restrictive definitions for identifying symptomatic infection in noncatheterized long-term care residents applied in the study by Juthani-Mehta et al increases the likelihood of ascertainment of true symptomatic UTI and gives confidence that the results are valid and the observations meaningful. 
 
 Other clinical trials have evaluated the use of cranberry products in older women.5- 8 Two of these, including one by the same authors, also reported no benefits of cranberry capsules5 or juice.6 One study, enrolling primarily older women (n =158) in the community,7 reported a decrease in bacteriuria with pyuria in individuals receiving cranberry juice, but this observation was likely confounded by a substantially higher frequency of symptomatic infection reported in the 6 months prior to enrollment for the placebo group. A recent study of the efficacy of cranberry capsules8 reported a benefit for older women (n = 401) and men (n = 115) residing in long-term care facilities who were judged to be at high risk of UTI, when a nonprecise definition for symptomatic infection was applied. However, when the more restrictive definition for symptomatic UTI was applied, there were no differences between participants randomized to receive cranberry capsules or placebo. Thus, prior studies in this population have also reported no benefits with cranberry products or have methodological issues that may compromise the reported outcomes. The current study, together with the observations in previous reports, is convincing in supporting a conclusion that cranberry products given to women residing in nursing homes without indwelling catheters do not improve outcomes of UTI for this population. 
 
 Clinical trials evaluating the use of cranberry juice or capsules in other patients at high risk of recurrent UTI have also reported conflicting results. Studies have enrolled young women with recurrent acute uncomplicated UTI, children with complicated or uncomplicated UTI, patients with spinal cord injuries, and other groups. Some recent studies that are of high methodological quality also report negative outcomes. Barbosa-Cesnik et al9 enrolled 319 female university students following an initial episode of acute uncomplicated UTI into a clinical trial evaluating cranberry juice to prevent further symptomatic episodes. There were no differences in the number of women experiencing recurrent symptomatic infection between the 2 study groups during 6 months of follow-up. In a study of 221 premenopausal women in the Netherlands with both complicated or uncomplicated recurrent UTI,10 trimethoprim/sulfamethoxazole was superior to cranberry capsules for preventing UTI during 1 year of therapy, despite a prevalence of trimethoprim/sulfamethoxazole resistance of more than 70% in the gut flora of the antibiotic cohort. These studies in other populations also support the conclusion that cranberry juice or capsules are not effective for the prevention of UTI in populations of women characterized by a high frequency of recurrent UTI. This is also the conclusion of an updated Cochrane review evaluating cranberries for preventing UTI,11 which notes, “cranberry juice cannot currently be recommended for the prevention of UTI’s”—a difference from the recommendation of the initial Cochrane review of this topic published 6 years earlier. 
 
 Some recent studies have reported benefits with cranberry products. In one trial involving 160 women who had gynecological surgery, use of cranberry capsules was associated with a 50% reduction (19% vs 38%) in the proportion of women who experience a UTI within 6 weeks postoperatively.12 This was an impressive result, but reasons that the intervention should be so effective in these women but not in other populations are unclear. The study analysis was potentially compromised by high noncompletion rates (> 50%), and an imbalance in randomization with respect to the occurrence of patient risk factors, including specific operative procedures and postoperative use of intermittent catheters for voiding. Further critical evaluation in this or other highly specialized populations may still be warranted. 
 
 The continuing promotion of cranberry use to prevent recurrent UTI in the popular press or online advice seems inconsistent with the reality of repeated negative studies or positive studies compromised by methodological shortcomings. Any continued promotion of the use of cranberry products seems to go beyond available scientific evidence and rational reasoning. Some of this conviction is likely an interest of individuals or groups to promote the use of natural health products for clinical benefits, allowing avoidance of medical interventions and, potentially, giving women who experience recurrent UTI an element of personal control in managing their problem. The current emphasis on antimicrobial stewardship and limiting antimicrobial use whenever possible also may have some influence in the continued endorsement of cranberry juice or tablets as a nonantimicrobial strategy for management of UTI. 
 
 What should be the current view of the role of cranberry products for prevention of recurrent UTI in women? The evidence, further supported by the study by Juthani-Mehta et al in an important population, is convincing that cranberry products should not be recommended as a medical intervention for the prevention of UTI. A person may, of course, choose to use cranberry juice or capsules for whatever reason she or he wishes. However, clinicians should not be promoting cranberry use by suggesting that there is proven, or even possible, benefit. Clinicians who encourage such use are doing their patients a disservice. Recurrent UTI is a common problem that is distressing to patients and because it is so frequent and costly for the health care system. It is time to identify other potential approaches for management. This certainly must include a wiser use of antimicrobial therapy for syndromes of recurrent UTI in women in long-term care facilities. Other possible interventions to explore in this and other populations may include, among other approaches, adherence inhibitors or immunologic interventions. Intellectual discussions and clinical trial activity should be redirected to identify and evaluate other innovative antimicrobial and nonantimicrobial approaches. It is time to move on from cranberries. 
 
 Back to top Article Information 
 
 Corresponding Author: Lindsay E. Nicolle, MD, FRCPC, Department of Internal Medicine, University of Manitoba, 820 Sherbrook St, GG 443, Winnipeg, Manitoba, Manitoba R3A 1R9, Canada (LNicolle@exchange.hsc.mb.ca). 
 
 Published Online: October 27, 2016. doi:10.1001/jama.2016.16140 
 
 Conflict of Interest Disclosures: The author has completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. 
 
 References 

 BACKGROUND: 
 
 Cranberries have been used widely for several decades for the prevention and treatment of urinary tract infections (UTIs). This is the third update of our review first published in 1998 and updated in 2004 and 2008. 
 
 OBJECTIVES: 
 
 To assess the effectiveness of cranberry products in preventing UTIs in susceptible populations. 
 
 SEARCH METHODS: 
 
 We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL in The Cochrane Library) and the Internet. We contacted companies involved with the promotion and distribution of cranberry preparations and checked reference lists of review articles and relevant studies.Date of search: July 2012 
 
 SELECTION CRITERIA: 
 
 All randomised controlled trials (RCTs) or quasi-RCTs of cranberry products for the prevention of UTIs. 
 
 DATA COLLECTION AND ANALYSIS: 
 
 Two authors independently assessed and extracted data. Information was collected on methods, participants, interventions and outcomes (incidence of symptomatic UTIs, positive culture results, side effects, adherence to therapy). Risk ratios (RR) were calculated where appropriate, otherwise a narrative synthesis was undertaken. Quality was assessed using the Cochrane risk of bias assessment tool. 
 
 MAIN RESULTS: 
 
 This updated review includes a total of 24 studies (six cross-over studies, 11 parallel group studies with two arms; five with three arms, and two studies with a factorial design) with a total of 4473 participants. Ten studies were included in the 2008 update, and 14 studies have been added to this update. Thirteen studies (2380 participants) evaluated only cranberry juice/concentrate; nine studies (1032 participants) evaluated only cranberry tablets/capsules; one study compared cranberry juice and tablets; and one study compared cranberry capsules and tablets. The comparison/control arms were placebo, no treatment, water, methenamine hippurate, antibiotics, or lactobacillus. Eleven studies were not included in the meta-analyses because either the design was a cross-over study and data were not reported separately for the first phase, or there was a lack of relevant data. Data included in the meta-analyses showed that, compared with placebo, water or not treatment, cranberry products did not significantly reduce the occurrence of symptomatic UTI overall (RR 0.86, 95% CI 0.71 to 1.04) or for any the subgroups: women with recurrent UTIs (RR 0.74, 95% CI 0.42 to 1.31); older people (RR 0.75, 95% CI 0.39 to 1.44); pregnant women (RR 1.04, 95% CI 0.97 to 1.17); children with recurrent UTI (RR 0.48, 95% CI 0.19 to 1.22); cancer patients (RR 1.15 95% CI 0.75 to 1.77); or people with neuropathic bladder or spinal injury (RR 0.95, 95% CI: 0.75 to 1.20). Overall heterogeneity was moderate (I² = 55%). The effectiveness of cranberry was not significantly different to antibiotics for women (RR 1.31, 95% CI 0.85, 2.02) and children (RR 0.69 95% CI 0.32 to 1.51). There was no significant difference between gastrointestinal adverse effects from cranberry product compared to those of placebo/no treatment (RR 0.83, 95% CI 0.31 to 2.27). Many studies reported low compliance and high withdrawal/dropout problems which they attributed to palatability/acceptability of the products, primarily the cranberry juice. Most studies of other cranberry products (tablets and capsules) did not report how much of the 'active' ingredient the product contained, and therefore the products may not have had enough potency to be effective. 
 
 AUTHORS' CONCLUSIONS: 
 
 Prior to the current update it appeared there was some evidence that cranberry juice may decrease the number of symptomatic UTIs over a 12 month period, particularly for women with recurrent UTIs. The addition of 14 further studies suggests that cranberry juice is less effective than previously indicated. Although some of small studies demonstrated a small benefit for women with recurrent UTIs, there were no statistically significant differences when the results of a much larger study were included. Cranberry products were not significantly different to antibiotics for preventing UTIs in three small studies. Given the large number of dropouts/withdrawals from studies (mainly attributed to the acceptability of consuming cranberry products particularly juice, over long periods), and the evidence that the benefit for preventing UTI is small, cranberry juice cannot currently be recommended for the prevention of UTIs. Other preparations (such as powders) need to be quantified using standardised methods to ensure the potency, and contain enough of the 'active' ingredient, before being evaluated in clinical studies or recommended for use. 

 Up to 60 percent of women will experience at least one urinary tract infection (UTI) in their lifetime, and if you’ve ever had one, you’ll know how unbearable it can be. 
 
 For years now, some doctors have been recommending cranberry juice and tablets to patients as a way to either prevent recurring UTIs or treat the symptoms, but a new study has found no difference between people treated with cranberries or placebos. 
 
 In fact, if you look back at all the scientific literature on the subject, you’ll find that either the recommended amount of cranberry juice is far beyond what’s realistic for an actual human being, or that there’s no solid evidence that any amount is having a positive effect. 
 
 "[C]linicians should not be promoting cranberry use by suggesting that there is proven, or even possible, benefit," Lindsay E. Nicolle, an expert on UTIs from the University of Manitoba, wrote in an editorial accompanying the new study. 
 
 "It is time to move on from cranberries." 
 
 The study, led by infectious disease specialist Manisha Juthani-Mehta from the Yale School of Medicine, investigated the effects of high-dose cranberry capsules - the equivalent of 591 ml (20 ounces) of juice every day - on 185 women in a nursing home. 
 
 Elderly women were chosen as the sample because among nursing home residents, UTIs are the most commonly diagnosed infection. 
 
 Up to half of all women living in nursing homes test positive for bacteriuria (bacteria in the urine), and 90 percent of those will test positive for pyuria (the presence of bacteria and white blood cells in the urine). Those two symptoms combined are good sign that a UTI is present. 
 
 The participants were split into two groups, and randomly assigned either two cranberry capsules a day - each containing 36 milligrams of the active ingredient proanthocyanidin - or a placebo. 
 
 Before the study had begun, 31 percent of the participants had tested positive for bacteriuria plus pyuria in their urine. 
 
 After 360 days of taking either the placebo or the cranberry capsules, the participants had their levels of bacteriuria and pyuria measured. 
 
 The researchers found no difference in the presence of bacteriuria plus pyuria between the cranberry group and the placebo group, and they found no differences in the number of UTI episodes either. (Thirty-eight participants ended up dropping out the study because the daily capsules were too much of a hassle, or had died for unrelated reasons, so the results are based on the remaining 147 participants.) 
 
 "The continuing promotion of cranberry use to prevent recurrent UTI in the popular press or online advice seems inconsistent with the reality of repeated negative studies or positive studies compromised by methodological shortcomings," says Nicolle. 
 
 "Any continued promotion of the use of cranberry products seems to go beyond available scientific evidence and rational reasoning." 
 
 For anyone following the UTI-cranberry juice saga closely, these results will not be a surprise - a lack of evidence for cranberry juice or capsules as being an effective preventative measure or treatment has been a recurring theme in the scientific literature for years. 
 
 In fact, as Susan Scutti reports for CNN, a 2012 review of 24 studies totalling 4,473 participants found little evidence of positive effects, and concluded that cranberry juice "cannot be recommended for the prevention of UTIs". 
 
 Given that Ocean Spray’s cranberry juice cocktail is only 27 percent juice, it makes sense that something so watered down would be so ineffective, but based on the results of this recent study, even if you ramp things up by switching to highly concentrated capsules, you still don't see a discernible effect. 
 
 So why has this myth persisted for so long? There's a couple of reasons - firstly, the active ingredient in cranberries, A-type proanthocyanidins (PACs), have been shown to block the adhesion of bacteria to the wall of the bladder. 
 
 So a reasonable hypothesis is that if bacteria are causing UTIs, something that blocks them from accumulating in the bladder could be a potential treatment or preventative measure. 
 
 "For a UTI to occur, bacteria must adhere to and invade the lining of the bladder," Timothy Boone from the Texas A&M College of Medicine, who wasn't involved in the study, told Newswise. "PACs interfere with the bacteria’s ability to bind to the wall of the bladder and create an infection." 
 
 But there's one problem. "It takes an extremely large concentration of cranberry to prevent bacterial adhesion," says Boone. "This amount of concentration is not found in the juices we drink. There’s a possibility it was stronger back in our grandparents' day, but definitely not in modern times." 
 
 And now we have evidence that the concentration of PACs in capsules is also not strong enough to prevent bacteria from accumulating in the bladder. 
 
 The second reason the myth is so persistent is it's such a tempting myth to believe. If you experience recurring UTIs and want to prevent them, or you want to feel empowered while you're waiting for the antibiotics to kick in, drinking cranberry juice or taking capsules is a pretty easy way to feel like you're helping. 
 
 At best, though, you're paying a lot of money for something that's only really doing the same job as a glass of water. 
 
 "It can offer more hydration and possibly wash bacteria from your body more effectively, but the active ingredient in cranberry is long-gone by the time it reaches your bladder," says Boone. 
 
 So save your cash and ditch the cranberry juice. It's full of sugar anyway. 
 
 The study has been published in the Journal of the American Medical Association, and the accompanying editorial is here.
– Among things all females learn early on is that you guzzle cranberry juice to prevent a urinary tract infection, which one in five women will eventually get. The reason: cranberries contain proanthocyanidins, or PACs, which can keep bacteria from sticking to the bladder and urinary tract. That's why a JAMA study published Thursday is so shocking: Leaving the "world rocked," per the New York Daily News, researchers say the idea is nothing more than an old wives' tale. After analyzing 147 older women in nursing homes—where UTIs are the most commonly diagnosed infection, per CNN—they found no variance in the number of UTIs among patients given 72 milligrams of PAC daily in cranberry capsules (the equivalent of 20 ounces of juice) and those given placebos, reports Science Alert. There was also no difference in terms of bacteria found in urine. "Although our study was only in nursing home women, many other studies have been done in other populations, which have not shown a benefit," says lead author Manisha Juthani-Mehta. For example, a 2012 review of 24 studies on cranberry juice, which is still touted by the American Congress of Obstetricians and Gynecologists, determined it "cannot be recommended for the prevention of UTIs." Paying for cranberry capsules with "limited potential benefit" for preventing UTIs, therefore, "does not seem worthwhile," says Juthani-Mehta. Another option: "For postmenopausal women, topical estrogen in the vagina has [been] shown to decrease the risk of UTI," a scientist says. (There is science behind this old wives' tale.)