The connection between cranberry juice and bladder infection, or cystitis, lies in evidence that supports the anti-pathogenic mechanism of the berries of the cranberry shrub, a creeping evergreen, on bacterial populations that cause the condition. The bacteria most commonly associated with bladder infection are Escherichia Coli, or E. Coli, which commonly infect various parts of the urinary tract, including the bladder. Before the bladder becomes infected, however, other parts of the tract are often times infected first. Studies show that the cranberry juice and bladder infection connection is more of a prophylactic action than a curative one because it primarily works on E. Coli populations that have already been established in the urinary tract. In most cases, by the time a patient presents with symptoms of a bladder infection, more aggressive treatment with antibiotic medications is needed.
There have been numerous studies done on the topic of cranberry juice and bladder infection, both as a prophylactic and as a curative. One mechanism by which the cranberry has been shown to fight against an E. Coli infection is causing a communication breakdown amongst the bacterial populations. Bacteria communicate with a process called quorum sensing. Quorum sensing works by a bacterium secreting a substance called an indole, which facilitates cellular reception of chemical signals. A chemical constituent of cranberry, proanthoyanidin, inhibits the secretion of indole and thereby inhibits effective communication.
E. Coli bacteria attach to uroepithelial cells by growing fimbre, which are protein-based projections that connect to certain sugar-based receptors on the cell. Proanthoyanidin blocks this process as well, and, in effect, causes the mechanism to fail, leaving the bacteria unable to attach to the host uroepithelial cell wall. In order to cause a widespread infection, bacteria must first adhere to a host and gather enough peers by quorum sensing to form a biofilm, which can then cause a pathogenic reaction. This process is interrupted by cranberry juice, which can often negate an infection.
Other studies of cranberry juice and bladder infection suggest that there are more anti-pathogenic properties at work. Cranberry juice contains citric acid, which causes increased acidity of urine. Increased hippuric acid can clear a urinary tract infection because E. Coli needs an alkaline environment to develop. Drinking water is recommended by physicians in the event of most types of infection, and this is especially true when dealing with infections of the urinary tract. Fruit juice is high in water content, and this may be another reason why cranberry juice has been shown to be effective against urinary disorders.