D-mannose is a form of sugar found in fruits and in supplement form. It is similar to glucose and occurs naturally in some cells of the human body. D-mannose treats carbohydrate-deficient glycoprotein syndrome and prevents and treats urinary tract infections, according to WebMD.
D-mannose appears naturally in many fruits, occurring in high amounts in apples, oranges, peaches, blueberries and cranberries. D-mannose is also available as a supplement that is taken by mouth, notes WebMD.
D-mannose treats carbohydrate-deficient glycoprotein syndrome type 1b, a rare genetic metabolic disorder that causes the patient to lose nutrients through the intestine, as explained by WebMD. Some studies suggest that d-mannose slows this protein loss and helps the liver function better. It may also help low blood sugar and bleeding disorders in patients with this syndrome.
Studies performed on animals suggest that d-mannose stops certain types of bacteria from adhering to the bladder walls, as noted by WebMD. Instead the bacteria stick to the sugar and pass through the body through urine, reducing the risk of infection. These studies have only been performed on animal subjects, so scientists are uncertain of the effects in human patients.
Animal studies also suggest that d-mannose is beneficial as a prebiotic, a substance that helps stimulate the growth of good bacteria in the digestive system, according to WebMD. These studies suggest that d-mannose may be helpful for people with an imbalance of good and bad bacteria, a condition known as dysbiosis.
Side effects of d-mannose include bloating and loose stools. In high doses it may cause kidney damage. As of November 2014, there is not enough research to determine the appropriate dosage for d-mannose, according to WebMD. Women who are pregnant or breastfeeding should take caution when using D-mannose because not enough studies have been done to prove its safety in these circumstances. People with diabetes should also use caution when taking D-mannose because it may make it more difficult to control blood sugar.