|Fructose is a simple carbohydrate widely distributed in organism, plants, and animals. Fructose in the body may be changed into glucose by the liver and intestines. As glucose it is used by the body in several ways, including as a source of energy. Fructose is the sweetest of sugars. It is much sweeter than sucrose (cane sugar). It is best obtained by hydrolysis of inulin, a polysaccharide
found in dahlia bulbs and the Jerusalem artichoke. Fructose is classified as a monosaccharide, the most important ketose sugar, a hexose, and is a reducing sugar. An older common name for fructose is levulose, after its levorotatory property of rotating plane polarized light to the left.
Fructose is used to sweeten some diet foods. It is considered a nutritive sweetener because it has calories. Fructose is one of the three most important blood sugars along with glucose and galactose. Fructose is implicated in producing obesity, elevated LDL cholesterol and triglycerides, leading to metabolic syndrome. It is used therapeutically as a fluid and nutrient replenisher. Fructose also chelates minerals in the blood. This effect is especially important with micronutrients such as copper, chromium and zinc.
Fructose is found in fruits, honey, and the sole sugar in bull and human semen. Fructose is more commonly found together with glucose and sucrose in honey and fruit juices. Bees gather nectar from flowers which contains sucrose. They then use an enzyme to hydrolyze or break apart the sucrose into its component parts of glucose and fructose. Glucose and fructose are formed in equal amounts when sucrose is hydrolyzed by the enzyme invertase or by heating with dilute acid; the resulting equimolar mixture of fructose and glucose, called invert sugar, is the major component of honey. Fructose depends on glucose to carry it into the blood stream. Absorption of fructose without glucose present is very poor, and excess fructose is carried into the lower intestine where it provides nutrients for the existing flora, which produce gas.
Hereditary fructose intolerance is an inherited condition where the body does not produce the chemical needed to break down fructose (fruit sugar). Fructose intolerance is a disorder caused by the body's inability to produce an enzyme called aldolase B that is necessary for absorption of fructose. The undigested fructose collects in the liver and kidneys, eventually causing liver and kidney failure. In fructose-intolerant people, ingestion of fructose (fruit sugar) and sucrose (cane or beet sugar, table sugar) produces complicated chemical changes that cannot be corrected because of the absence of the enzyme aldolase B. Ingestion of fructose causes profound hypoglycemia (low blood sugar) and progressive liver damage. The body is unable to convert its energy storage material, glycogen, into glucose. Urine tests can be used to detect fructose sugar in the urine. Blood tests can also be used to detect hyperbilirubinemia and high levels of liver enzymes in the blood. Fructose intolerance can be successfully treated by eliminating fructose from the diet.