Suggested mechanism of action

• cranberries comprise nearly 90% water - however cranberries also contain various organic substances including catechin, flavonoids, anthocyanins and many organic acids
  • there has been no definite mechanism of action established for cranberry in the treatment or prevention of UTIs
  • the main proposed mechanism is that cranberry inhibits the adhesion of infecting bacteria (e.g. Escherichia coli) to the uroepithelium
    • if the adhesion of adhesion, E. coli, for example, is inhibited then the bacteria cannot infect the mucosal surface of the urinary tract
    • two components of cranberry inhibit adhesion in vitro:
      • proanthocyanidins - inhibits the adherence of p-fimbriated (alpha-galactose-(1-4) specific) E. coli
      • fructose - inhibits adherence of type 1 (mannose-specific) fimbriated E. coli
    • other suggested mechanisms of action proposed for cranberry include its ability to acidify urine and the antiseptic effect of some of its contents, such as hippuric acid - however these suggested mechanisms are less plausible than the effect on bacterial adhesion (1)

Reference:

1. Drug and Therapeutics Bulletin 2005; 43(3):17-19.