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New Research Finds Increased Water Intake Helps Prevent Recurrent Bladder Infections, Reduces Use of Antibiotics in Premenopausal Women

Health Letter, January 2019

By Michael Carome, M.D.

water prevent UTIs
Image: KieferPix/Shutterstock.com

Many women are plagued by frequent bladder infections. For years, several behavioral measures have been recommended to decrease the risk of having recurrent bladder infections — such as increased fluid intake, improved pelvic hygiene, avoidance of contraceptive spermicides and urinating soon after sexual intercourse — but there has been a lack of evidence from well-designed randomized clinical trials to support these recommendations.[1]

However, a team of researchers from the U.S. and Europe recently completed the first randomized clinical trial to evaluate the effectiveness of increased water intake for the prevention of recurrent bladder infections in premenopausal women. Their findings, which were published in the November issue of the Journal of the American Medical Association (JAMA) Internal Medicine, demonstrated that this simple and safe behavioral intervention was very effective for reducing the risk of recurrent bladder infections and the use of antibiotics to treat such infections.[2]

About bladder infections

Acute bladder infection is one of the most common infections in women. The lifetime risk of having a bladder infection in women exceeds 50 percent.[3] Common symptoms of such infections include needing to urinate more frequently, urgency (the sudden urge to urinate due to involuntary contractions of the bladder muscles), dysuria (a burning or painful sensation when urinating) and lower abdominal-pelvic pain in the area of the bladder.

Many women suffer from recurrent bladder infections, which can significantly decrease their quality of life. For example, one study found that more than a quarter of college-age women who have their first bladder infection will experience at least one recurrent infection within 6 months.[4]

Importantly, use of antibiotics to treat bladder infections comprises a major proportion of antibiotic use around the globe, and some women also are prescribed long-term antibiotics to prevent frequent recurrences of these infections. In addition to exposing women to the risk of adverse effects of these drugs, such widespread use of antibiotics contributes to the spread of antibiotic-resistant bacteria, which the Centers for Disease Control and Prevention has flagged as a growing worldwide public health threat.[5] Identifying effective approaches to prevent common infections and thus minimize the use of antibiotics is a critical public health priority.

The JAMA Internal Medicine trial [6]

In this trial, which took place at a medical research center in Bulgaria, researchers enrolled 140 otherwise healthy premenopausal women age 18 or older who had had three or more symptomatic acute bladder infections that resulted in a visit to a health care professional in the preceding year. For at least one of the prior bladder infections, the women had to have had a positive urine culture confirming a bacterial infection. To be eligible for the trial, the women also had to self-report drinking less than 1.5 liters (a liter is about one quart) of fluid per day. The enrolled women had a mean age of 36, and 92 percent of them reported being sexually active in the month prior to enrollment.

The researchers randomly assigned the subjects in equal numbers to either an experimental water group or a control group. The water group subjects were instructed to drink 1.5 liters of water daily in addition to their usual fluid intake. To facilitate compliance, these women were provided with three half-liter bottles of water to be consumed daily, along with guidance to start a bottle of water at the beginning of every meal and fully drink it before the next meal. The control group subjects did not drink additional fluids.

The women were then followed for 12 months. They were instructed to contact the research staff or another health care professional any time they experienced urinary symptoms in order to obtain a urine culture. The primary outcome of interest was the frequency of bladder infections that were confirmed by a positive urine culture over 12 months. To assess compliance with their assigned fluid intake, subjects were asked to complete three-day fluid intake diaries each month. In addition, at six and 12 months after enrollment, the subjects collected urine for 24 hours to assess total daily urine volume, which provides a more objective assessment of actual fluid intake. Ninety-three percent of the subjects completed 12 months of follow-up.

The effect of the increased water intake on the rate of recurrent bladder infections was striking. Over the 12-month trial period, there were 111 bladder infections in the water-group subjects and 216 in the control-group subjects. The average number of bladder infections per subject was 1.7 in the water group and 3.2 in the control group, a difference that was highly statistically significant and corresponded to a nearly twofold decrease in the frequency of infections among the water-group subjects.

Consistent with the trial’s primary results, the water group received an average of 1.9 courses of antibiotic treatment for bladder infections per subject, compared with 3.6 in the control group — another nearly twofold difference. The median time to the first bladder infection was 148 days in the water group and 94 days in the control group.

As intended, the fluid-group subjects had large increases in average self-reported daily fluid intake, 24-hour urine volumes at six and 12 months, and number of daily urinations compared with baseline levels, whereas no such changes occurred in the control-group subjects. Finally, the occurrence of reported adverse events — most commonly headaches and gastrointestinal symptoms — was similar in both groups.

The trial did have some notable limitations. First, it was not possible to conduct the trial using a double-blinded design, a procedure that is intended to minimize bias in randomized trials by preventing both the researchers and the subjects from knowing each subject’s group assignment. Second, the study was funded by Danone Research, which sells bottled water, including the Evian water used in the trial, and four of the researchers were employed by Danone Research.

Despite these limitations, the trial otherwise appears to have been designed and conducted in a rigorous manner. Although clearly not 100 percent effective, the trial provides strong evidence that increasing water intake is a simple, safe and effective measure for significantly reducing the risk of recurrent bladder infections and the exposure to potentially harmful antibiotics in premenopausal women — benefits that likely would extend to other women.

The effectiveness of increased fluid intake in preventing bladder infections is likely due to increases in urine volume and dilution and in the number of daily urinations, all of which help reduce the amount of bacteria in the bladder.

And women who have recurrent bladder infections don’t need to purchase Evian or any other type of bottled water to achieve the health benefits of increased water intake. As one of the JAMA Internal Medicine editors noted in a published comment about the trial, “it seems clear that any safe-to-drink water will do, including your local tap water, which will also spare the environmental impact of bottled water and improve the cost-effectiveness of the intervention.”[7]


[1] Hooton TM, Gupta K. Recurrent simple cystitis in women. UpToDate. October 17, 2018. https://www.uptodate.com/contents/recurrent-simple-cystitis-in-women. Accessed December 10, 2018.

[2] Hooton TM, Vecchio M, Iroz A, et al. Effect of increased daily water intake in premenopausal women with recurrent urinary tract infections: A randomized clinical trial. JAMA Intern Med. 2018;178(11):1509-1515.

[3] Ibid.

[4] Foxman B. Recurring urinary tract infection: incidence and risk factors. Am J Public Health. 1990;80(3):331-333.

[5] Centers for Disease Control and Prevention. Antibiotic Resistance Threats in the United States, 2013. http://www.cdc.gov/drugresistance/threat-report-2013/pdf/ar-threats-2013-508.pdf. Accessed December 10, 2018.

[6] Hooton TM, Vecchio M, Iroz A, et al. Effect of increased daily water intake in premenopausal women with recurrent urinary tract infections: A randomized clinical trial. JAMA Intern Med. 2018;178(11):1509-1515.

[7] Grady D. Editor’s note: Drinking more water for prevention of recurrent cystitis. JAMA Intern Med.em> 2018;178(11):1515.