Fructose, or levulose, is a levorotatory monosaccharide and an isomer of glucose (C6H12O6). The chemical composition of fructose is (C6H12O6). Pure fructose has a sweet taste similar to cane sugar, but with a "fruity" aroma. Although fructose is a hexose (6-carbon sugar), it generally exists as a 5-member hemiketal ring (a furanose). This structure is responsible for the long metabolic pathway and high reactivity compared to glucose. Fructose is found in many foods and is one of the three most important blood sugars along with glucose and galactose. Honey, tree fruits, berries, melons, and some root vegetables, such as beets, sweet potatoes, parsnips, and onions contain fructose, usually in combination with sucrose and glucose. Fructose is also derived from the digestion of sucrose, a disaccharide consisting of glucose and fructose that is broken down by enzymes during digestion. Fructose is the sweetest naturally occurring sugar, estimated to be twice as sweet as sucrose. It is used as a preservative and an intravenous infusion in parenteral feeding. Fructose is a reducing sugar, as are all monosaccharides. The spontaneous addition of single sugar molecules to proteins, known as glycation, is a significant cause of damage in diabetics. Fructose appears to be as dangerous as glucose in this regard, and therefore does not seem to be the answer for diabetes (McPherson et al, 1988). This may be an important contribution to senescence and many age-related chronic diseases (Levi & Werman 1998).