In galactosemic patients, the accumulation of galactose becomes the substrate for enzymes that catalyze the polyol pathway of carbohydrate metabolism. The first reaction of this pathway is the reduction of aldoses, types of sugars including galactose, to sugar alcohols.[6] Recent data suggests that aldose reductase is the enzyme responsible for the primary stage of this pathway. Therefore, aldose reductase reduces galactose to its sugar alcohol form, galactitol.