Carbohydrate Digestion

Carbohydrate is a naturally occurring organic substance. Some common forms of dietary carbohydrates include sugars, starch and cellulose. Carbohydrates is categorized into four different types. They are: monosaccharide, disaccharides, polysaccharides and complex carbohydrate. Monosaccharides are glucose, fructose (present in fruits) and galactose. Disaccharides are sucrose (present in table sugar), lactose (present in milk) and maltose. Digestion of mono and di-saccharides occurs quite rapidly. However, digestion of polysaccharides like starch requires a lot of time while very complex carbohydrate digestion is not possible at all. A common example of complex carbohydrate is the cellulose that are present in the plant fiber which act as bulking agents in the digestive system. The speed of digestion depends on the chemical composition of the specific carbohydrate. The more complicated is the molecular structure the longer will be the time taken for digestion.

Carbohydrate Digestion and Absorption

Basically, digestion of carbohydrate involves conversion of the large molecules of carbohydrates like di-saccharides and polysaccharides into simple mono-saccharide molecules which can be easily absorbed by the body. The first step of digestion is the moment we put the food in mouth. As we chew the food, the saliva released by the salivary glands of the mouth starts its work of breaking up of the carbohydrates. This is possible because of the presence of a special enzyme named amylase in the saliva. Then we swallow the food and it goes to the stomach. Here the digestive acids secreted by the glands of the stomach play a major role in processing the carbohydrate molecules further. The digestive enzymes of the stomach also helps in this work but they do not have much significant role in digestion in the stomach.

From the stomach, small amounts of the food enters the small intestine where most part of the carbohydrates are digested. The first section of the small intestine is duodenum which receives a form of amylase enzyme released from the pancreas gland for the purpose of carbohydrate digestion. Here, carbohydrate molecules are further converted into simple molecules of sucrose, lactose and maltose. While passing through the small intestine some more enzymes named maltase, lactase and sucrase are involved in the process which breaks down the maltose, lactose and sucrose into smaller bits to ensure easy absorption of the digested sugar through the intestinal lining and from there to the bloodstream. The indigestible part of the complex carbohydrates like dietary fiber is transferred to the colon and from there it is excreted by bowel movement.

As the end product of carbohydrate digestion get absorbed into the bloodstream, the blood sugar level of our body rises from its normal level. Soon pancreas gland secretes insulin hormone so that the newly absorbed glucose can be "sucked up" from blood and get it converted into glycogen which is then stored up inside the liver and distributed to various muscles. This stored glycogen is utilized by the body to obtain energy to carry out various activities. If the glycogen storage capacity of the liver and muscles becomes full, the excess amount of glucose is converted into fat and is stored in the fat stores of the body.

There are two types dietary carbohydrates that are present in our foods. One is the naturally occurring carbohydrates obtained from fruits, potatoes, beans, etc. The other one is artificial or man-made which can be found in white bread, white rice, etc. Use of natural carbohydrates is always recommended and are considered as better source of energy. This is because the excess of man-made carbohydrates have a greater tendency to get accumulated as fats in the body. Moreover, natural carbohydrates is a rich source of dietary fiber and other useful nutrients which are absent in man-made carbohydrates.