The cranberry, native to North America, has long been hailed as a cure and preventative for urinary tract infections but how much truth is there in this?
In the past, cranberries were linked to UTIs and cystitis for two reasons: firstly because of their acidity (cranberries contain a range of acids: citric, malic, benzoic, quinic) which was thought kill off bacteria, and secondly because they contain high levels of Proanthocyanidins and Flavonols (thought to decrease adherence of E-coli with fimbriae to the cell walls).
We now know that many strains of bacteria, including strains of E.coli (the bacterium which causes of the vast majority of UTI’s), actually thrive in an acid environment. Also, studies have shown that, whilst Proanthocyanidins and Flavonols do increase the levels of energy that E-Coli needs to expend to attach to cells, they are not able to prevent bacteria from multiplying. They have been shown to be successful, to some degree, in protecting against Streptococcus mutans and H-Pylori bacteria but the European Food Safety Authority in 2011 found claims about Proanthocyanidins in relation to E-Coli in UTIs to be unsubstantiated.
Nonetheless, testing of the properties of cranberries in relation to UTIs found a component that could in fact be more helpful: D-Mannose.
D-Mannose occurs naturally, in small amounts, in cranberries but needs to be taken in larger quantities to be effective against E.coli. In order to gain any effectiveness from drinking cranberry juice as a preventative for UTIs, you would have to drink two 220ml glasses of cranberry juice three times a day (or take a cranberry extract 300-400mg twice a day) for a number of months (Lynch, 2006). Though studies have shown that even at this level of consumption cranberries may only prevent a maximum of 50% of UTIs from occurring (Jepson et al, 2012).
EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2011. Scientific Opinion on the substantiation of health claims related to proanthocyanidins from cranberry (Vaccinium macrocarpon Aiton) fruit and defence against bacterial pathogens in the lower urinary tract (ID 1841, 2153, 2770, 3328), “powerful protectors of our gums” (ID 1365), and “heart health” (ID 2499) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal 2011;9(6):2215, 18 pp. doi:10.2903/j.efsa.2011.2215
Howell, A. (2007). Bioactive compounds in cranberries and their role in prevention of urinary tract infections. Molecular Nutrition & Food Research, 51(6), pp.732-737.
Jepson RG, Williams G, Craig JC. Cranberries for preventing urinary tract infections. Cochrane Database of Systematic Reviews 2012, Issue 10. Art. No.: CD001321. DOI: 10.1002/14651858.CD001321.pub5.
Lynch, D. M. (2004). Cranberry for prevention of urinary tract infections. American Family Physician, 20, 2175-2177.
Porru, D., Parmigiani, A., Tinelli, C., Barletta, D., Choussos, D., Di Franco, C., Bobbi, V., Bassi, S., Miller, O., Gardella, B., Nappi, R., Spinillo, A. and Rovereto, B. (2014). Oral D-mannose in recurrent urinary tract infections in women: a pilot study. Journal of Clinical Urology, 7(3), pp.208-213.
Toyota S, Fukushi Y, Katoh S, Orikasa S, Suzuki Y . Anti-bacterial defense mechanism of the urinary bladder. Role of mannose in urine. Nippon Hinyokika Gakkai Zasshi 1989 Dec;80(12):1816-23.
Following the application made by Ocean Spray related to their cranberry products, theEFSA Panel concluded in 2009 "the evidence provided is not sufficient to establish a cause and effect relationship between the consumption of O S cranberry products and the reduction f the risk of UTI in women by inhibiting the adhesion of certain bacteria in the urinary tract." The full Summary of Opinion given by EFSA is given on their website:
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