Ch. 04 Carbohydrate
File: 2 Introduction
Carbohydrates are an important source of fuel for body cells. Carbohydrates are organized in
molecules that are in single (monosaccharide), double (disaccharide), or multiple (polysaccharide)
units. Glucose, fructose, and galactose are examples of monosaccharides; sucrose, lactose, and
maltose of disaccharides; and starch and fiber of polysaccharides.
There are three primary carbohydrate groups: sugars, oligosaccharides, and polysaccharides.
Examples of sugars include the monosaccharides glucose and fructose; the disaccharides sucrose
and lactose; and the polyols sorbitol and mannitol. Examples of oligosaccharides include maltodextrin
and raffinose. Examples of polysaccharides include starch and fiber.
File: 3 Introduction
Digestion of carbohydrate begins in the mouth with salivary amylase, and continues in the small
intestine with pancreatic amylase. For absorption to take place in the intestine, disaccharides and
polysaccharides must be further reduced. This is accomplished by enzymes called disaccharidases.
Sometimes, necessary enzymes are missing and an intolerance results. Lactose intolerance is caused
by an inability to produce lactase, an enzyme which is necessary for digestion of milk sugar.
When body supplies of glucose, a carbohydrate, are adequate, ingested protein is used for body
maintenance, repair, and growth. When it is not, protein is used for fuel. Recommendations for daily
carbohydrate intake are based on the minimal amount needed to prevent ketosis a condition
characterized by incomplete combustion of fats resulting in elevated blood ketone levels.
Recommended daily intake of carbohydrate is less than most people eat.
File: 4 Introduction Fiber
First described in the 1970s, the term dietary fiber describes carbohydrate derived from plant cell walls
including cellulose, hemicellulose, and non-starch polysaccharides. There is a lack of agreement
concerning which types of carbohydrate qualify as dietary fiber. Although widely used, the terms
soluble and insoluble are inexact. Fiber has three forms: fermentable, non-fermentable, and viscous.
Each form contributes to health in a different way. One of the most important is to provide bulk that
promotes a healthy tone in intestinal muscles.
File: 5 Introduction Metabolism