The term "carbohydrates" encompasses a diverse group of substances, many of which are important to your health. In fact, carbohydrates probably comprise your main source of dietary energy. As their name implies, carbohydrates are composed of carbon and water, and all carbohydrates contain carbon, hydrogen and oxygen atoms in a 1:2:1 ratio. While the chemical proportions of all carbohydrates are the same, these three elements can be arranged in different ways to form a wide array of simple sugars and polysaccharides.
Classification
Scientists classify carbohydrates according to their chemical structure. Two main types of nutritional carbohydrates are found in plants, the sole producers of these important compounds. Free sugars, which are readily digested and absorbed into your bloodstream, include monosaccharides, such as glucose, fructose and galactose; disaccharides, such as lactose -- the only sugar produced by animals -- sucrose and maltose; and oligosaccharides, which contain up to 20 monosaccharides hooked together. Polysaccharides, the second main division, typically contain several dozen to many hundreds of monosaccharides within the same molecule. The polysaccharides are further subdivided into starches and non-starch polysaccharides.
Starches
According to scientists at Elmhurst College, plants produce starches as a means to store glucose, which is a source of cellular energy. Thus, starches are large, compact molecules composed of repeating units of glucose. If the starch molecule is long and straight without any branches, it is called amylose. If it is branched at various points along its length, the starch is called amylopectin. In both amylose and amylopectin, the glucose units are hooked together by special bonds called alpha-acetal linkages. This linkage is readily broken apart by digestive enzymes in your gastrointestinal tract.
Non-Starch Polysaccharides
Like starches, non-starch polysaccharides consist of long chains of repeating glucose units. However, unlike starches, the glucose units in non-starch polysaccharides are joined by bonds called beta-acetal linkages. The beta-acetal linkage cannot be split by the enzymes in your digestive tract. Certain animals -- cows, goats, sheep, horses and termites -- have bacteria in their guts that cleave the beta-acetal linkage. Non-starch polysaccharides include celluloses, hemicelluloses, gums, pectins, xylans, mannans, glucans and mucilages.
Benefits
Despite their relative indigestibility, non-starch polysaccharides are important to your health. In his book "Staying Healthy with Nutrition," Dr. Elson Haas reports that these compounds boost detoxification processes in your liver, enhance your immune function, regulate your blood sugar, stabilize your appetite, lower your cholesterol and improve your bowel activity. Some non-starch polysaccharides, such as beta-glucans from mushrooms, appear to possess anti-tumor properties. Thus, rather than being inert, non-nutritious filler in your food, non-starch polysaccharides offer a cornucopia of benefits.
References
- "Staying Healthy With Nutrition: Carbohydrates"; Elson M. Haas, M.D.; 2006
- Elmhurst College: Virtual Chembook -- Starch
