- Monosaccharides (simple sugars)
- Hexoses
- Glucose: honey, fruits, corn syrup, sweet grapes, sweet corn; hydrolysis of starch and cane sugar. Physiologically the most important sugar; the “sugar” carried by the blood and the principal one used for tissues.
- Fructose: honey, ripe fruits, some vegetables; hydrolysis of sucrose insulin. Can be changed to glucose in the liver and intestine and is an intermediate metabolite in glycogen breakdown.
- Galactose: not found free in nature; digestive end product of lactose hydrolysis. Can be changed to glucose in the liver; synthesized in body to make lactose and is a constituent of glycolipids.
- Mannose: found in legumes; hydrolysis of plant mannosans and gums. A constituent of polysaccharide of albumins, globulins, and mucoids.
- Pentoses
- Arabinose: derived from gum arabic plus plum and cherry gums; not found free in nature. Has no known physiologic function in man; used in metabolism studies of bacteria.
- Ribose: derived from nucleic acid of meats and seafoods. Structural element of nucleic acids, ATP, and coenzymes (NAD and FAD).
- Ribulose: formed in metabolic processes. Intermediate in direct oxidative pathway of glucose breakdown.
- Xylose: wood gums, corncobs, and peanut shells; not found free in nature. Very poorly digested and has no known physiologic function; used medicinally as a diabetic food.
- Hexoses
- Oligosaccharides (2-10 sugar units)
- Disaccharides
- Sucrose: cane and beet sugar, maple syrup, molasses, and sorghum. Hydrolyzed to glucose and fructose; a non-reducing sugar.
- Maltose: malted products and germinating cereals; an intermediate product of starch digestion. Hydrolyzed to two molecules of glucose; a reducing sugar; does not occur free in tissues.
- Lactose: milk and milk products; formed in the body from glucose nature. Hydrolyzed to glucose and galactose; may occur in urine during pregnancy; a reducing sugar.
- Trisaccharides
- Raffinose: cottonseed meal, molasses, sugar beets and stems. Only partially digestible but can be hydrolyzed by enzymes of intestinal bacteria to glucose, fructose, and galactose.
- Melizitose: honey, poplars, and conifers. Composed of one fructose unit and two glucose units.
- Disaccharides
- Polysaccharides (more than 10 sugar units)
- Digestible
- Glycogen: meat products and seafoods; polysaccharides of the animal body, often called animal starch; storage form of carbohydrates in body, mainly in liver and muscle.
- Starch: cereal grains, unripe fruits, vegetables, legumes, and tubers. Most important food source of carbohydrates; storage form of carbohydrates in plants. Composed chiefly of amylose and amylopectin; hydrolyzed to glucose.
- Dextrin: toasted bread, intermediate product of starch digestion. Formed in course of hydrolytic breakdown of starch.
- Partially Digestible
- Inulin: tubers and roots of dahlias, artichokes, dandelions, onions, and garlic. Hydrolizable to fructose; used in physiologic investigation for determination of glomerular filtration rate.
- Mannosan: legumes and plant gums. Hydrolyzable to mannose but digestion incomplete; further splitting by bacteria may occur in large bowel.
- Indigestible
- Cellulose: skins of fruits, outercoverings of seeds, plus stalks and leaves of vegetables. Not subject to attack of digestive enzymes in man, thus an important source of “bulk” in diet; may be partially split to glucose by bacterial action in large bowel.
- Hemicellulose and pectin: woody fibers and leaves. Less polymerized than cellulose; may be digested to some extent by microbial enzymes, yielding xylose.
Indigestible is another name for indigestable polysaccharides is dietary fiber which is comprised of 2 groups:
- Insoluble dietary fibers (cellulose, lignin, and cutin) which are the most abundant organic compounds in the world. They help prevent constipation, colon cancer, and diverticulosis, but not hypercholesterolemia.
- Soluble dietary fibers (hemicellulose, pectins, gums, and algal polysaccharides) which are useful in decreasing serum cholesterol and in regulating blood glucose levels.
- Digestible