About the study
Recent research out of the Yale School of Medicine suggests that cranberry supplements don’t help to prevent or cure urinary tract infections (UTIs). This study was published online in the Journal of the American Medical Association on Thursday, October 27, 2016.
In this study, researchers looked at 147 women 65 years of age and older (with an average age of 86), who were living in nursing homes, and who were randomly assigned to take either two cranberry capsules or placebo pills daily for a period of one year. Over the course of the study, researchers compared the total number of UTIs and other markers in the urine known to promote infection in both groups of women to see whether taking cranberry pills had any benefit.
At the beginning of the study (before cranberry capsules were even given), almost one-third of the women tested positive for the presence for bacteria and white blood cells. Although this doesn’t mean the women had UTIs at the start of the study, it is important to note that bacteria and white blood cells in the urine are factors that contribute to the occurrence of a UTI.
What did the study find?
Overall, the researchers found no significant difference between the women who took cranberry pills or a placebo when comparing how many of them had evidence of a UTI. There was also no significant difference in the number of women who experienced overt symptoms of a UTI during the course of the study (10 women who were taking cranberry pills compared to 12 women in the placebo group).
What does this mean to me?
Cranberry is traditionally used to help prevent recurring urinary tract infections caused by E. coli and other bacteria, as it may help to prevent the bacteria from attaching to urinary tract walls. It is recommended by Health Canada as a natural option for treating UTIs and supported by science (see studies in footnote).
While reviewing the study findings, there are some key factors to consider:
- Health Canada recommends 10-30 g of fresh cranberry fruit per day, or up to 950 mL per day of cranberry fruit juice for effective treatment and prevention of UTI infections. Study participants were given the equivalent of 591 mL of cranberry juice in supplement form. Therefore, better results may have been seen with a higher daily dose as per Health Canada’s recommendation.
- For cranberry to be effective, it is important to take it at the proper dosage for at least four weeks. The authors of this study have noted that there is a possibility that participants weren’t taking the prescribed amount for the entire duration of the study.
- The researchers didn’t exclude participants who had a positive screen for bacteria at the time of enrollment, so it wasn’t possible to determine the role of cranberry in either the prevention of a new occurrence or a reduction of bacteria and white blood cells in the urine.
- This study was done in a small group of women 65 years of age and older living in nursing homes, and the results are not necessarily applicable to younger, healthy adults living outside of a nursing home setting. Staying hydrated is also important for helping to prevent UTIs, and we do not know whether participants were properly hydrated throughout the course of the study.
- There were some positive results seen in the study group taking cranberry supplements that have not been reported in the media, such as a faster decline in UTI symptoms than those taking the placebo.
Cranberry remains a recognized, Health Canada approved natural solution for preventing recurrent urinary tract infections. As everyone is different, some may find cranberry more effective than others. For women who are looking to prevent or manage recurrent urinary tract infections, it’s important to speak to your healthcare practitioner for a proper diagnosis and to determine whether cranberry supplements are right for you.
Walker EB, Barney DP, Mickelsen JN, Walton RJ, Mickelsen RA. Cranberry concentrate: UTI prophylaxis. Journal of Family Practice 1997;45(2):167-168.
Lavigne J, et al. (2008). In-vitro and in-vivo evidence of dose-dependent decrease of uropathogenic Escherichia coli virulence after consumption of commercial Vaccinium macrocarpon (cranberry) capsules. Clinical Microbiology and Infection, 14(4): 350–355.
McMurdo M, et al. (2009). Cranberry or trimethoprim for the prevention of recurrent urinary tract infections? A randomized controlled trial in older women. Journal of Antimicrobial Chemotherapy, 63(2): 389-95.
Raz R, et al. (2004). Cranberry juice and urinary tract infection. Clinical Infectious Diseases, 38(10):1413-1419.
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