Cranberry Juice as a Cure for Urinary Tract Infections: Truth or Myth?

By Cristina Piñel Neparidze

Here’s an interesting statistical fact: about 60% of women will experience urinary tract infections (UTIs) at some point in their lives. This common (and incredibly irritating) condition develops when microbes (most common ones being bacteria such as Escherichia Coli, Klebsiella Aerogenes and certain Enterobacter species) enter the urinary tract and cause a bladder infection (Behzadi et. al., 2010). 

Common treatment for this condition includes antibiotic-based treatments such as sulfamethoxazole, trimethoprim and nitrofurantoin (Kranz et. al., 2018) though, in the case of recurrent UTIs, these types of drugs are currently posing a risk for the emergence of antibiotic resistance (Hisano et. al., 2012). Interestingly, one of the most widely held beliefs amongst women who experience recurrent UTI infections is that consuming cranberry juice (or alternatively taking cranberry supplements) can prevent as well as cure them. 

Within the scientific community, this widely held assumption has sparked a lot of debate; Results from a number of published clinical studies have supported its benefit, however, meta-analyses on cranberry and UTI prevention have reported conflicting conclusions (Liska et. al., 2016). When carrying out cranberry-related research within the context of UTIs, scientists hypothesised that cranberries work principally by preventing the adhesion of type 1 and p-fimbriae strains (proteins that enable bacteria such as E. coli to adhere to the host tissue) to the urothelium (the epithelial cells lining the lower urinary tract). Without adhesion, the bacteria cannot infect the mucosal surface, and are therefore unable to survive in the bladder for too long (Hisano et. al., 2012).

This hypothesis has encouraged the implementation of many clinical trials aiming to test the clinical relevance of cranberry on UTI prevention and cure. A highly cited study that disproves the alleged benefits of cranberry juice is that of Barbosa-Cesnik et. al. (2011), who reported that women drinking cranberry juice during a 6-month period did not present a lower UTI recurrence in comparison to women taking a placebo. Cranberries have additionally been compared with antibiotic trimethoprim for UTI prevention in a randomized, controlled study in women older than 45. The six-month risk of developing a UTI while consuming cranberries was 60% greater than in women on low-dose trimethoprim; however, this result did not reach statistical significance (McMurdo, et. al., 2008).

As for studies supporting the benefits of cranberries, a research study done on 2006 suggested that daily dosages of 240–300 ml of cranberry juice cocktail could prevent 50% of the recurrences of UTIs and could decrease bacteriuria (Bruyère, 2006). Moreover, ex vivo study examining human urine following cranberry juice cocktail consumption suggested that twice-a-day dosages of cranberries could offer additional protection during a 24 h period (Gupta et. al. 2010). 

As mentioned before, these conflicting studies undoubtedly have sparked some heated conversations about the controversial effectiveness of cranberry juice or cranberry-derived consumables when it comes to urinary tract infection prevention or treatment. Some review papers have suggested that this conflict might be mainly attributed to differences in study design and analysis approaches (Liska et. al., 2016), but it is clear that further research is imperative to establish a more informed conclusion. Meanwhile, if a patient suspects a UTI, doctors usually advise to drink cranberry juice because, useful or not, you don’t lose anything by trying!

References:

1. Behzadi, P., Behzadi, E., Yazdanbod, H., Aghapour, R., Akbari Cheshmeh, M. & Salehian Omran, D. (2010) A survey on urinary tract infections associated with the three most common uropathogenic bacteria. Mædica; Maedica (Buchar). 5 (2), 111-115.

2. Kranz, J., Schmidt, S., Lebert, C., Schneidewind, L., Mandraka, F., Kunze, M., Helbig, S., Vahlensieck, W., Naber, K., Schmiemann, G. & Wagenlehner, F. M. (2018) The 2017 Update of the German Clinical Guideline on Epidemiology, Diagnostics, Therapy, Prevention, and Management of Uncomplicated Urinary Tract Infections in Adult Patients: Part 1. Urologia Internationalis; Urol Int. 100 (3), 263-270. Available from: doi: 10.1159/000486138.

3. Hisano, M., Bruschini, H., Nicodemo, A. C. & Srougi, M. (2012) Cranberries and lower urinary tract infection prevention. Clinics (São Paulo, Brazil); Clinics (Sao Paulo). 67 (6), 661-667. Available from: doi: 10.6061/clinics/2012(06)18.
4. Liska, D. J., Kern, H. J. & Maki, K. C. (2016) Cranberries and Urinary Tract Infections: How Can the Same Evidence Lead to Conflicting Advice? Advances in Nutrition (Bethesda, Md.); Adv Nutr. 7 (3), 498-506. Available from: doi: 10.3945/an.115.011197.

5. Cibele Barbosa-Cesnik, Brown, M. B., Buxton, M., Zhang, L., DeBusscher, J. & Foxman, B. (2011) Cranberry Juice Fails to Prevent Recurrent Urinary Tract Infection: Results From a Randomized Placebo-Controlled Trial. Clinical Infectious Diseases; Clin Infect Dis. 52 (1), 23-30. Available from: doi: 10.1093/cid/ciq073.

6. McMurdo, M. E. T., Argo, I., Phillips, G., Daly, F. & Davey, P. (2009) Cranberry or trimethoprim for the prevention of recurrent urinary tract infections? A randomized controlled trial in older women. Journal of Antimicrobial Chemotherapy; J Antimicrob Chemother. 63 (2), 389-395. Available from: doi: 10.1093/jac/dkn489.

7. Bruyère, F. (2006) Use of cranberry in chronic urinary tract infections. Médecine Et Maladies Infectieuses; Med Mal Infect. 36 (7), 358-363. Available from: doi: 10.1016/j.medmal.2006.05.001.

8. Gupta, K., Chou, M. Y., Howell, A., Wobbe, C., Grady, R. & Stapleton, A. E. (2007) Cranberry Products Inhibit Adherence of P-Fimbriated Escherichia Coli to Primary Cultured Bladder and Vaginal Epithelial Cells. The Journal of Urology; J Urol. 177 (6), 2357-2360. Available from: doi: 10.1016/j.juro.2007.01.114.