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The idea that mannose supplements can help prevent or treat bladder infections derives from a property of the E. colibacteria. E. coliis one of the common causes of bladder infections. Many, though not all, strains of E. colihave the ability to attach to the mannose present in the wall of the bladder by means of thread-like structures called pili. This process of attachment allows them to initiate the process of infection.
Reasoning from this fact of basic science, medical researchers in the 1980s hypothesized that consumption of mannose as a supplement will increase levels of mannose in the urine to such an extent that this free mannose will saturate the E. coli’smannose-binding pili and thereby make the bacteria unable to grapple onto the cells of the bladder wall.
It is essentially this reasoning that is restated by proponents of mannose for bladder infections. However, the argument has at least four problems. First, one of the main ways that the body’s white blood cells recognize and kill E. coliis via these mannose-sensitive pili. 1 When these pili are saturated by mannose, white blood cells (specifically, macrophages) are less able to consume the E. colibacteria. 2 Second, many species of E. coli, including some of the most dangerous, do not have mannose-sensitive pili at all. 3 Third, there are numerous other bacteria that cause bladder infections, and these are not known or suspected to have mannose-sensitive pili.
But perhaps the most important point is that the use of mannose for preventing or treating bladder infections has never undergone any meaningful scientific study in human beings. There is a bit of evidence from animal studies performed in the 1980s, 4 but it is a long way from animal studies to efficacy in humans. Proponents of mannose also cite numerous testimonials, but the placebo effect and related confounding factors are quite sufficient to produce numerous testimonials for any treatment. Only double-blind, placebo-controlled studies can actually prove a treatment effective, and none have been performed on mannose.
The bottom line: There is no meaningful scientific reason to believe that mannose is useful for the prevention or treatment of bladder infections.
- Blumenstock E, Jann K. Adhesion of piliated Escherichia coli strains to phagocytes: differences between bacteria with mannose-sensitive pili and those with mannose-resistant pili. Infect Immun. 1982;35:264-269.
- Felipe I, Bochio EE, Martins NB, et al. Inhibition of macrophage phagocytosis of Escherichia coli by mannose and mannan. Braz J Med Biol Res. 1991;24:919-924.
- van der Bosch JF, Verboom-Sohmer U, Postma P, et al. Mannose-sensitive and mannose-resistant adherence to human uroepithelial cells and urinary virulence of Escherichia coli. Infect Immun. 1980;29:226-233.
- Michaels E, Chmiel J, Plotkin B, Schaeffer A. Effect of D-mannose and D-glucose on Escherichia coli bacteriuria in rats. Urol Res. 1983;11:97-102.