home
contents
psychcorner       
family matters
wellness  
this & that
diet & nutrition 
heal the world
spirituality
library
links
about us

submit articles  
to CrescentLife

ask the expert

Carbohydrates
Types of Carbohydrates: Monosaccharides, Disaccharides, Polysaccharides

Carbohydrates are sugars and starches. Our bodies use carbohydrates as fuel for the energy it needs to perform all its functions: ie: breathing, digesting, laughing, walking, etc. 

Monosaccharides (simple sugars): These include fructose (fruit sugar) and glucose, often called blood sugar because it's what all carbohydrates are broken down into in the body. Only glucose circulates in the blood, providing energy to organs, glands, muscles, indeed to every cell. Finally, there is galactose, which rarely stands alone but does combine with other simple sugars, notably with glucose to form lactose (milk sugar).

Disaccharides (double sugars): are bonded pairs of simple sugars. There is sucrose (table sugar), glucose plus fructose; lactose (milk sugar), glucose plus galactose; and maltose (malt sugar), two linked glucose molecules.  Honey is the only natural sweetener.

Polysaccharides (complex carbohydrates): are chains of glucose molecules, they digest more slowly than simple or double sugars. Found in peas, beans, legumes, grains, potatoes and other starchy plants.

All carbohydrates equal 4 calories per gram.  Nutritionists recommend taking 55 to 60 percent of your daily calories from carbohydrates. 

Sugars or simple carbohydrates are found primarily in:
Fruits and vegetables.
Fiber, including cellulose, hemicellulose, and pectin - found in whole-grain legumes, vegetables, and fruits.
Molasses - simple sugar.
Natural fruit sugars.

Carbohydrates are the most abundant food, and are the principle source of energy used throughout the world. However, excess consumption of the simple carbohydrates, especially table sugar and possibly even honey, cause great nutritional deficiencies. Sugar, for instance, contains none of the essential minerals or vitamins needed for its metabolism. Honey does contain 22 amino acids and a variety of minerals. Other diseases caused by excess carbohydrates are heart disease, colon cancer, obesity, and dental decay.

The simple sugars are monosaccharides. These include glucose, which occurs in corn sugar and grape sugar, as well as dates, and to varying degrees, in fruits.

Fructose, which is fruit sugar, is found in honey, ripe fruits, and to a slight extent, in some vegetables. It is over twice as sweet as glucose, and twice as sweet as cane sugar (a disaccharide or oligosaccharide).

Galactose is produced when milk sugar, or lactose, is broken down.

Mannose is a somewhat more complicated simple sugar, as are xylose and arabinose, as well as ribose. Xylose, arabinose, and ribose are bicarbon simple sugars, and all of these are produced during digestion of fruits, and to some extent, meat.

Sucrose, which is common table sugar, is usually derived from sugar cane or sugar beets, but it can be derived from sorghum grain, molasses or maple sugar as a disaccharide containing one molecule of fructose and one molecule of glucose. A very small amount of sucrose is found in some vegetables and in some fruit, but in its natural form, always contains vitamins and minerals.

Lactose is the only significant sugar or carbohydrate of animal origin. The amount in different species ranges from 2 to 8% of the milk. It has one molecule of glucose and one molecule of galactose. An enzyme, lactase, is essential for digestion of lactose, and a majority of adults in this country do not have lactase, which digests milk sugar, or lactose. Thus, it is very difficult for them to digest milk and may contribute to gaseousness, cramping, and diarrhea.

Maltose, or malt sugar, is a somewhat longer chain of glucose molecules, and it is manufactured during the breakdown, or hydrolysis of starch.

All starches are polysaccharides, which consist of long chains of glucose. Starch is broken down by an enzyme called amylase into dextrin, which consists of shorter chains of glucose units, somewhat closer to maltose than they are to the other sugars.

Glycogen, our human-made carbohydrate, is actually produced in the liver and in muscle, and is formed from blood glucose, the in-body source of energy.

There are a number of indigestible polysaccharides, including cellulose, hemicellulose, lignin, agar, alginate, and carrageen. 

Amounts of complex carbohydrates in 
Grains contain 68 to 84% carbohydrates by dry weight
Dry legumes 60 to 63%. 
Dried fruit 59 to 69% carbohydrates
Fresh fruit, 6 to 22%. 
White potatoes, raw, are 17% carbohydrates
Dry rice is 80% complex carbohydrates. 
Nuts average 15 to 20% carbohydrates. 

One gram of carbohydrate yields four calories of energy, or one ounce of carbohydrate yields 120 calories of energy. Fiber assists in regulating gastrointestinal transient time, facilitates adequate bowel evacuation, and excretion of cholesterol. Lack of adequate fiber leads to hemorrhoids, probably hiatal hernia, diverticulosis of the colon, as well as appendicitis. A high-fiber diet reduces the rate of colon and rectal cancers as well as heart disease and diabetes. Simple sugars are absorbed rapidly and tend to raise the blood sugar fairly rapidly.

Sucrose, interestingly, even though it needs to be broken down, tends to raise the blood sugar more rapidly than almost any other simple carbohydrate. Ultimately, all energy in the body is obtained by burning various foods, which must be converted into materials that feed into something called the Kreb cycle. The Kreb cycle essentially produces energy. Digestion of the more complex carbohydrates begins in the mouth with salivary amylase, and then in the small intestine. The pancreas releases sucrases, amylases, lactates, and maltases, which need an alkaline environment to break carbohydrates down into monosaccharides. All carbohydrates, ultimately, are then converted into glucose. If there is an excess over immediate need for the glucose, it is converted into glycogen or fat.

 

[ Up ]