Cranberries + Urinary Tract InfectionsMany people know that cranberries help maintain urinary tract health. Research is now showing just how cranberry juice promotes urinary tract health…and why cranberries are the only food with this benefit.
For many years, people thought drinking cranberry juice was beneficial because the juice was thought to increase the acidity of urine in the bladder and therefore kill the bacteria that cause urinary tract infections. This is not the case.
It turns out that cranberries contain compounds called proanthocyanidins (PACs) that have strong bacterial anti-adhesion properties. PACs interfere with the ability of bacteria to adhere to the cells that line the bladder wall. Instead of sticking to the bladder wall and causing an infection (and the subsequent pain), the bacteria get flushed out in the urine.
While other foods like apple juice, grape juice and green tea contain proanthocyanidins (PACs), cranberries are the only food that contain PACs with A-type linkages (as opposed to B-type linkages). The unique molecular structure explains why cranberries are the only food associated with urinary tract health.
E. coli bacteria cause 80-90% of urinary tract infections. Proanthocyanidins (PACs) from cranberries affect E. coli cells in three ways. Cranberry PACs (1) change the shape of the E. coli from rods to sphers, (2) alter the cell membranes, and (3) compress tendrils on the outside of the cells, which affects E. coli’s ability to attach to cells lining the bladder wall. All of these effects inhibit the bacteria’s ability to attach to cells lining the bladder wall.
The anti-adhesion property of cranberry juice and cranberry juice cocktail has been demonstrated in many lab and human studies. (1-3) However, only one study has examined the anti-adhesion property of sweetened dried cranberries. (4) This small pilot study of five human subjects compared the effects of sweetened dried cranberries and unsweetened raisins. Only the subjects who consumed the dried cranberries exhibited anti-adhesion activity. More research is needed to support this finding, but it looks like sweetened dried cranberries may also help promote urinary tract health.
(1) Jepson RG, Craig JC. Cranberries for preventing urinary tract infections. Cochrane Database Syst Rev. 2008;1:CD001321.
(2) Di Martino P, Agniel R, David K, Templer C, Gaillard JL, Denys P, Botto H. Reduction of Escherichia coli adherence to uroepithelial cells after consumption of cranberry juice: a double-blind randomized placebo-controlled cross-over trial. World J Urol. 2006;24(1):21-27.
(3) Howell AB, Reed JD, Krueger CS, Winterbottom R, Cunningham DG, Leahy M. A-type cranberry proanthocyanidins and uropathogenic bacterial anti-adhesion activity. Phytochemistry. 2005; 66(18): 2281-91.
(4) Greenberg JA, Newmann SJ, Howell AB. Consumption of sweetened dried cranberries versus unsweetened raisins for inhibition of uropathogenic Escherichia coli adhesion in human urine: a pilot study. J Altern Complement Med. 2005;11(5):875-8.