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Teaching Nutrition: Background information about nutrition, the nutrients, and healthy eating habits
 
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Carbohydrates
 

Bags and sheaves of grains.

Carbohydrates are organic molecules constructed in the ratio (CH2O)n in a variety of lengths and shapes. Carbohydrates are the body’s preferred source of energy; the other potential energy sources being proteins and fats. Carbohydrates are broken down in the body into sugars, starches, and fiber. The sugars are known as simple carbohydrates, and the starches and fiber are known as complex carbohydrates. (Alcohol is also considered a class of carbohydrates but will not be discussed in this section.)


Function
Carbohydrates perform three important functions in the body:

  • Supply energy
  • Supply fiber
  • Aid in the digestion of fats

 

Monosaccharides
 
Disaccharides
 
Polysaccharides
Monosaccharides are the simplest form of carbohydrates. The monosaccharides are glucose, galactose, and fructose. Sugars and starches are broken down in the body into the simple sugar glucose. Glucose is the major sugar found in the bloodstream and supplies energy for the body. Some body tissues, such as red blood cells and parts of the brain, are able to get energy only from glucose. Fructose is found in honey and fruits and is known as the sweetest of the sugars. Galactose is not found in nature, but it is one of the two monosaccharides available after the breakdown of lactose (milk sugar).   Disaccharides are formed when two monosaccharides are joined together. They are broken down into their monosaccharide components during digestion. The disaccharides are sucrose, maltose, and lactose. Sucrose (glucose + fructose) is found in white, refined table sugar, brown sugar, confectioner’s sugar, cane sugar, beet sugar, molasses, and maple syrup. Maltose (glucose + glucose) is malt sugar which is found in sprouting cereal grains. Lactose (glucose + galactose) is milk sugar and is found only in milk.   Polysaccharides are the complex carbohydrates often consisting of very long chains of glucose monomers. They include starch, cellulose, and glycogen. Starch is the most abundant polysaccharide and is an important storage form of energy in plants. Starch can be found in roots (such as potatoes), legumes, grains, and vegetables, but must be broken down into glucose by the body before it can be utilized. Cellulose is the fibrous material found in plants, such as the strings in celery, and is commonly referred to as fiber or roughage. Cellulose cannot be digested by humans. Sources of cellulose include vegetables, fruits, and whole grain cereals. Glycogen, also known as animal starch, is the storage form of carbohydrates found in the liver and muscles. Glycogen in the liver is easily broken down into blood glucose, and muscle glycogen supplies glucose for muscle use. This is especially important during periods of intense exercise.

Forty-five to sixty-five percent of calories should come from complex carbohydrates. Preferred carbohydrate sources include vegetables, fruits, grains and grain products, legumes, and dairy products. Current recommendations suggest half of all grain and grain products consumed should be whole grains.

 

 
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