D-Mannose in Fruit

Elaine writes

Bacteria causing infections on human tissues have an affinity to bind to a certain sugar, d- mannose, on the cell membranes of tissue. D-mannose is a monosaccharide sugar found naturally in fruits and is similar to glucose except in its three-dimensional form (stereochemistry). Although no one has done research on its function, re its presence in the intestine, other than to indicate that it is involved in immunological reactions, there are reports on its therapeutic effect in the urinary tract where cranberry juice (containing much D-mannose) has a beneficial action in urinary tract infections. It is very possible that in intestinal infections, the d-mannose in fruit competes with the d-mannose on the cells in the gut and provides competition which would allow the infectious bacteria to leave their binding sites on the gut and attach to the d-mannose in fruit and, thereby, have a beneficial effect in lessening the infection.

Bacteria that are involved with gut pathology have been studied in ways that show how they initiate a response by the immune system. In most of these articles, there is the interaction of bacterial cell walls and their ability to bind to cells of the urinary tract and other mucosal cells (also the surface of the gut) through D-mannose receptors. It is referred to as lectin binding to D-mannose. The reason that cranberry juice has been used for urinary tract infections is because the bacteria causing the infections (E. coli where it should not be in the urinary tract but this would apply to many other bacterial species) is to "make" the bacteria adhere to the D-mannose in cranberry juice and let go of the tissue in the urinary tract or elsewhere.

D- Mannose is present in fruit, and although it may be there in lesser amounts than the monosaccharides, glucose and fructose, it is present. In addition to its natural occurrence in the cells lining the epithelial tract, the sugar D-mannose is also found in relatively large quantities in fruit such as peaches, pineapple, apples, oranges, and certain berries, like cranberries and blueberries.