Early Hypothesis About Urinary Tract InfectionThere has been much speculation about the mechanism by which cranberry products protect against Urinary Tract Infections.
In the early 1900s, one researcher observed that consumption of 300-600 g of cranberry sauce/d could promote short term changes in urine pH.
It was hypothesized that this acidification prevented bacterial colonization of the urinary tract epithelium.
Although this was the popular theory subsequent studies were unable to demonstrate that urinary pH always acidified post-consumption.
However, because urinary hippuric acid excretion also increased after cranberry consumption, that substance was suggested as being responsible for the protective effects.
By the 1960s, it was determined that cranberry juice altered urine pH for only a short period of time, that the degree of acidification was not sufficient to provide bacteriological or bacteriostatic effects and that neither acidification nor hippuric acid could be the primary mechanisms.
In 1984, the researcher used E. coli isolates form people with UTIs to determine that cranberry juice contains a non-dialyzable material that specifically inhibits the expression of the p-fimbria of bacteria, hence preventing their attachment to and colonization of the urinary tract.
Given the large body of evidence showing that cranberry juice does not modify urine pH and UTI incidence it is surprising that acidification is still mentioned in current news.
Early Hypothesis About Urinary Tract Infection
