This study demonstrates that the sugar molecule, D-mannose is at least as effective as, and better tolerated than, a commonly used antibiotic for preventing recurrences of UTIs. The use of D-mannose for preventing and treating UTIs was pioneered some 20 years ago by Jonathan Wright, M.D. Although D-mannose has become popular in recent years, evidence of its efficacy was entirely anecdotal until the publication of the present study. For the treatment of an acute UTI, Wright recommends a dosage of 1 teaspoonful (about 2 g) for adults and 1/2 to 1 teaspoonful for children, dissolved in a glass of water or juice and repeated every 2 to 3 hours. For prevention of post-intercourse UTIs, the recommended dosage is 1 tablespoonful 1 hour prior to intercourse and again immediately afterwards.1 D-Mannose is apparently not effective for UTIs caused by organisms other than E. coli. Because of its safety and low cost, D-mannose is a useful alternative to antibiotics for the prevention and treatment of UTIs caused by E. coli.
It has generally been assumed that D-mannose works by preventing the adherence of pathogenic strains of Escherichia coli to uroepithelial cells. However, the concentration at which D-mannose exerts that effect is higher than what can be achieved in the urine after administration of the recommended dose. Moreover, once E. coli has adhered to the bladder wall, one could not necessarily expect that free D-mannose in the urine would successfully detach it from its cellular binding sites. Another possible explanation for the efficacy of D-mannose is its relationship to Tamm-Horsfall protein. This glycoprotein, which is produced by renal cells and excreted in the urine, plays a key role in the body's defense against UTIs. Tamm-Horsfall protein contains a large number of high-mannose structures, which appear to account for its infection-fighting activity.2 It is possible that orally administered D-mannose works primarily by facilitating the synthesis or promoting the activation of Tamm-Horsfall protein.
 Gaby AR. Nutritional Medicine, 2011, Concord NH, chapter 216. www.doctorgaby.com.
 Serafini-Cessi F, et al. N-Glycans carried by Tamm-Horsfall glycoprotein have a crucial role in the defense against urinary tract diseases. Glycoconj J 2005;22:383-394.