“Drink more water” for UTIs: testing the old wives’ tale

For decades the prevention of urinary tract infections (UTIs) was based on recommendations handed down as old wives' tales. "Drink cranberry juice" and "drink more water", based on my completely non-scientific polling of my patients, are the top two pieces of advice that women have been hearing, not only from other women, but also from medical professionals.

The thing about "old wives' tales" is that it's critical to subject them to rigorous scientific testing - ideally with randomized, controlled trials. Sometimes these remedies can be proven scientifically, and sometimes they can't. Take, for example, the recommendations for cranberry juice (see previous Health & Nutrition Bites here and here). The jury is still out on cranberry juice despite these recent studies. What about the advice on water?

Researchers affiliated with the School of Medicine at the University of Miami, UT Southwestern, and other researchers employed by Danone France (makers of Evian water, used in this study), designed a randomized controlled trial to assess the effects of additional water intake on women who had recurrent urinary tract infections (JAMA Int Med 2018;178(11):1509-1515).

The authors recruited 118 premenopausal women (average age about 35), who reported experiencing at least 3 instances of UTIs within the past year, with at least one case verified by their physician. The researchers further narrowed down the participants to those women who reported normally drinking less than 1.5 liters of fluid (including coffee, sodas, and all other liquids) per day, as measured by a 3-day fluid intake diary administered prior to the start of the study.

Women were excluded if they were pregnant, lactating, or planning to become pregnant, and those who had symptoms of UTIs or associated conditions at the start of the study were also excluded.

For 12 months, half of the women were provided with 3 500-milliliter bottles of Evian water to drink each day, over and above their usual liquid intake. The other half of the women were instructed to continue their usual intake of liquids.

All participants were instructed to contact the study staff or a physician of their choice any time they experienced a symptom associated with a urinary tract infection. When participants did so, the clinician or study staff performed a urine culture for diagnosis. Additionally, the staff contacted all participants once per month by phone to see if they had experienced any symptoms of a urinary tract infection and to urge them to have testing.

Over the course of the 12-month study, the women who increased their water intake experienced an average of 1.7 UTIs, while those who continued with their usual fluid intake (the control group) experienced about 3.2 instances. That's a nearly 50% reduction in UTIs in the women who increased their water intake.

What this means for you

In the past we've come down hard on studies that are funded by companies with a vested interest in the results. The difference here is that this study is of water and is funded by... a water company. The fact is that there is nothing special about Evian water: the same results could be obtained with water from the tap in your home.

What should engender caution is that the research was limited to women who already have a low level of fluid intake, so if your daily fluid intake totals 1.5 liters or more (which is less than you might think), this might not help you. If you are prone to frequent UTIs, keep a liquid diary: write down everything liquid you consume, from soups to coffee to alcohol to water, estimating amounts as best you can, for 3 days. Then share that diary and this column with your primary care physician and discuss with them whether you need to increase your fluid intake.

First posted: January 16, 2018