Sugar is the common term for a saccharide. In terms of nutrition, they are the elements that comprise carbohydrates and accordingly, are the source of the majority of the energy you consume. The sugar the human body uses for energy is always glucose, but it can convert other sugars into glucose to use them, as well. Sugars are chemically distinct because they all contain equal amounts of carbon, hydrogen and oxygen in asymmetrical configurations.
Monosaccharides
Monosaccharides are sugars that comprise one type of molecule. There are more than 200 known monosaccharides. However, the body can only metabolize three: glucose, fructose and galactose. While glucose is the only sugar the human body can actually use as energy, fructose naturally appears in its unbound state in fruits, while galactose appears in milk. Monosaccharides are simple sugars, as they require little effort by the body to metabolize, resulting in sharp rises in blood sugar levels.
Dissacharrides
Disaccharides, which comprise bonds of two sugar molecules, are also simple sugars. Unlike monosaccharides, disaccharides crystallize, making them easy to granulate. As a result, they are the most common stand-alone sweeteners. Examples include sucrose, or common white sugar, which contains fructose-glucose bonds. Another is lactose, which naturally appears in milk and contains galactose and glucose bonds. Maltose appears in vegetables and beer and contains double glucose bonds. High-fructose corn syrup, a sweetener often used by manufacturers, contains both fructose-glucose bonds and unbound fructose, rendering the fructose proportion slightly greater. Naturally occurring sugars, such as maple syrup, honey, agave nectar and sugar cane juice all contain combinations of monosaccharides and disaccharides. Sugar cane juice, for example, contains both sucrose as well as unbound fructose and glucose.
Polysaccharides
Polysaccharides contain bonds of three or more sugar molecules and are considered complex carbohydrates. They require more processing than simple sugars to metabolize, resulting in more moderate increases in blood sugar over a longer period. Accordingly, they are healthier sources of dietary energy. Examples are starch and fiber, both of which occur only in plants. Rather than containing a series of several types of sugars, starch contains a long chain of glucose bonds. This renders the carbohydrate insoluble, which makes it ideal as energy storage for plants. Fiber usually contains sugars that are not in the human diet, like cellulose, and are therefore indigestible. But, although it is not nutritive and does not provide energy, fiber still aids digestion in ways that makes it an invaluable addition to most healthy diets.
Alcohol
Alcohol has a similar chemical structure to sugar. This is because it is a derivative. Alcohol that humans can ingest in small amounts derive from sugars that appear in the human diet. They result when certain organisms, like yeast, digest sugars in an aqueous solution, converting them into alcohols. For example, wine results when yeasts break down the fructose that occurs in grapes and other fruits, converting them into alcohol over years. Grapes are the most common fruit used to create wine, because it contains the most fructose. Beer, on the other hand, results when yeast breaks down various simple and complex carbohydrates, like starches and other saccharides from barley, malt, molasses, hops, wheat, buckwheat and other grains.
References
- MedlinePlus; Carbohydrates; May 2010
- MedlinePlus: Carbohydrates
- University of Calgary: Saccharides
- "Chemical and Functional Properties of Food Saccharides"; Piotr Tomasik; 2004
- "Nutrition: Concepts and Controversies"; Frances Sienkiewicz Sizer and Ellie Whitney; 2008
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