Sugar is the generalized name for sweet, short-chained soluble carbohydrates. Carbohydrates are composed of carbon, hydrogen and oxygen (basically carbon + water). The term sugar refers loosely to a number of different types of carbohydrates, including monosaccharides (glucose, fructose), disaccharides (sucrose, lactose), oligosaccharides and polysaccharides (common components of glyco-proteins and glyco-lipids). The most biologically important and well known monosaccharide is glucose. Glucose is the main source of energy fueling aerobic metabolism… a fundamental necessity of living mammalian cells. The most common disaccharide is sucrose (glucose + fructose) or common table sugar. Bio-polymers (oligo and polysaccharides) of sugar are common structural forms of carbohydrates in nature. Plants produce sugar and sugar bio-polymers through the process of photosynthesis. These bio-polymers are converted into structural polysaccharides, such as cellulose and pectin found in plant cell walls. They also may serve as a form of energy storage, such as starch or inulin. In addition, DNA and RNA are polymers of the monosaccharides deoxyribose and ribose respectively and constitute the basis of genetic blueprint and memory for almost all forms of life. The importance of sugar in its various functional and structural forms for life cannot be overstated. However, like Oxygen, which is both essential for most life forms and also extremely toxic to life (physiologic function versus toxic free-radical damage), sugar also has a dark side for living tissue.
Studies in animals and humans have suggested that chronic consumption of added sugar contributes to metabolic and cardiovascular dysfunction. There is also growing evidence that added fructose is more damaging than refined glucose in terms of cardiovascular risk  Cardiac performance has been shown to be impaired by switching from a low carbohydrate diet including fiber to a high carbohydrate diet. Switching from saturated fatty acids to carbohydrates with high glycemic index values shows a statistically significant increase in the risk of myocardial infarction. Other studies have shown the risk of developing coronary heart disease is decreased by adopting a diet high in polyunsaturated fatty acids and low in sugar, but a low fat, high carbohydrate diet showed no reduction. This suggests that consuming a diet with high glycemic load (“high glycemic” = causes a rapid rise in blood sugar) is strongly associated with the development of coronary artery disease. The consumption of added sugars has been positively associated with multiple measures known to increase cardiovascular disease risk in adolescents as well as adults. Multiple studies suggest the impact of refined carbohydrates or high glycemic load carbohydrates is more significant than the impact of saturated fatty acids on cardiovascular disease.[6-26] In addition, a connection between Alzheimer’s disease and fructose has been suggested, but remains the subject of debate.[27,28] Finally, the possible addictive effects of refined sugar simply adds to the scientific concern regarding the toxic effects of sugar in the development of cardiovascular disease.