What is Mannose?

Mannose is a “six-carbon-sugar,” as are the better known and closely related substances glucose and fructose. Relying on evidence that is both exceedingly preliminary and highly inconsistent, some alternative medicine practitioners have popularized mannose as a treatment for urinary tract infections.

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.

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Safety Issues

As a sugar widely present in foods, mannose is assumed to be safe. However, the maximum safe dosage has not been established in healthy adults, nor in pregnant or nursing women or young children. Very weak evidence from test tube studies hints that consumption of gigantic amounts of mannose by pregnant women could conceivably increase risk of birth defects in their offspring. ^{1 2}