Nutritional Pearls: Cranberry Juice for UTIs

Martha is a 42-year-old woman with a history of several urinary tract infections (UTIs). At her most recent check-up, Martha expresses concern over antibiotic resistance—and asks if there are any lifestyle changes she might make that will help to prevent more UTIs in the future.

How do you advise your patient?
(Answer and discussion on next page)

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Answer: Drinking cranberry juice may help to prevent UTIs.

About 60% of women will experience at least 1 UTI in their lifetime, and as many as 35% will have another UTI within about 6 months. They are usually treated with antibiotics, and with an estimated 10.5 million office and emergency room visits attributed to UTIs, that's a significant contribution to rising rates of antibiotic resistance.

Back in 2013, a meta-analysis of about a dozen studies looked at drinking cranberry juice to prevent UTIs.¹ The results of the individual studies were mixed, but the more important issue, from the point of view of the authors of the meta-analysis, was the overall poor quality of the studies they were evaluating. Problems with these studies included short duration, small number of participants, unstandardized dosage, and a large number of participants dropping out of the studies. Any one of these issues can seriously impact the quality (and thus credibility) of the research, and the overall result was that nothing was really proven, scientifically speaking, either way.
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The Research

The good news is that a new team of researchers recruited 322 adult women aged 20 to 70 from 17 locations around the United States—and one in France—to participate in a 6-month study evaluating daily cranberry juice consumption on urinary tract infections.² These women had no major medical issues but had all experienced at least 2 UTIs within the year prior to the study's start date, with one UTI within 6 months of the start date.

Half the women were provided with 8 ounces per day of a cranberry-flavored beverage that contained no actual cranberry juice: the placebo. The other half were provided with the same daily amount of a cranberry beverage containing 27% cranberry juice from a single batch of cranberry juice concentrate (assuring that their daily beverage contained a standard amount of the active ingredient in cranberries). The women kept daily records of their consumption of their cranberry beverage as well as any urinary tract infection symptoms they might have. If symptoms occurred, the women were tested for a UTI, and if the test was positive (not all were), the women were treated with antibiotics.

The Results

The authors found that those women drinking the real cranberry juice beverage experienced 42% fewer urinary tract infections in the 6 months of the study than those women drinking the placebo beverage.

Unfortunately, there is bad news, as well: not only did Ocean Spray Cranberries, Inc provide the beverages for the research, 3 of the 6 authors on this paper received grant funding from Ocean Spray and 2 others are direct employees of Ocean Spray Cranberries.

What’s the “Take-Home”?

This is one of those studies that you have to take with a whole shaker full of salt. While the research might be well-designed, large enough, long enough, have reasonably few people dropping out of the study, and use standardized amounts of pure cranberry juice, the funding source irrevocably taints the results. By all means, if you feel that drinking cranberry juice every day helps you avoid urinary tract infections, go ahead and drink it. But be very cautious of anyone who cites this study as "proof" that it works.

Reference:

1. Jepson R, Craig J, Williams G. Cranberry products and prevention of urinary tract infections. JAMA. 2013;310(13):1395-1396.
2. Maki KC, Kaspar KL, Khoo C, Derrig LH, Schild AL, Gupta K. Consumption of a cranberry juice beverage lowered the number of clinical urinary tract infection episodes in women with a recent history of urinary tract infection. Am J Clin Nutr. 2016;103(6):1434-1442.