Cranberry Juice and UTIs

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Updated on April 10, 2014

You’ve known for years that cranberries can help stave off urinary tract infections (UTIs), but now scientists have figured out the mechanism behind the benefit!

In a study published in this month’s Colloids and Surfaces B: Biointerfaces, researchers from Worcester Polytechnic Institute in Massachusetts analyzed the Gibbs free energy of adhesion changes between bacteria and uroepithelial cells exposed to varying concentrations of cranberry liquids. In English? Essentially, the researchers extracted some cells from the inside of the urinary tract, threw in some bacteria, doused them with cranberry juice and watched to see how they would interact.

According to the researchers, when bacteria with fimbriae (a fancy term for hair-like projections on an organism) are exposed to even low concentrations of cranberry juice, the energy levels of the bacteria were increased to levels that made it difficult to attach to the urinary tract cell. Confused? So were we…until you consider that those hair-like projections are always present on the virulent bacteria responsible for causing UTIs and not on other, healthy bacteria.

Speaking to the mechanism behind the…uhhh…mechanism, the researchers suggest that the fact that the cranberry juice only affected bacteria with fimbriae suggests that something in the juice may directly change the molecular structure of the fimbriae themselves.

Commenting on the data, study author, Terri Camesano, notes that in the case of UTIs, “cranberry juice targets the right bacteria — those that cause disease — but has no effect on non-pathogenic organisms, suggesting that cranberry juice will not disrupt bacteria that are part of the normal flora in the gut.” In addition, Sano notes that “unpublished work also shows cranberry juice has potent effects on disease-causing bacteria, but that the effect is temporary.”

So how much juice are we talking here? Well, according to the researchers, fewer and fewer attachments were observed as the concentration of cranberry juice were increased, suggesting that in order to “realize the antibacterial benefits of cranberry, one must consume cranberry juice regularly, perhaps daily.” They do note, however, that regular cranberry juice cocktail and sugar-free cranberry juice both work equally well to reduce infections.

To keep it primal, we’d suggest adding a handful of raw cranberries to a salad (a 100g serving has 12 grams of carbs). If you’re in a rush though (or simply prone to UTIs) we’d suggest opting for a reduced sugar cranberry juice – just make sure it’s made with actual juice!