Carbohydrate Digestion and Absorption

Carbohydrate is a naturally occurring organic substance. Some common forms of dietary carbohydrates include sugars, starch, and cellulose. They are categorized into four different types such as: monosaccharides, disaccharides, polysaccharides, and complex carbohydrates. Monosaccharides are glucose, fructose (present in fruits), and galactose.

Disaccharides are sucrose (present in table sugar), lactose (present in milk), and maltose. Digestion of monosaccharides and disaccharides occurs quite rapidly. However, digestion of polysaccharides like starch requires a lot of time while that of complex carbohydrates is not possible at all.

A common example of complex carbohydrate is the cellulose that is present in the plant fiber, which acts as a bulking agent 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.

Basically, the digestion process involves the conversion of large molecules of carbohydrates like disaccharides and polysaccharides into simple monosaccharide molecules which can be easily absorbed by the body.

The process of digestion of carbohydrates begins in the mouth. As we chew the food, salivary glands secretes the enzyme called 'salivary amylase'. This enzyme breaks starch and glycogen into disaccharides.

Once the food is swallowed, it goes into the stomach. Here, the digestive acids secreted by the glands of the stomach play a major role in processing the molecules further.

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 the duodenum, which receives an enzyme called 'pancreatic amylase' released from the pancreas. This enzyme splits the molecules of starch and glycogen into disaccharides.

The inner wall of the small intestines is covered with tiny projections called the 'villi'. These projections play an important role in the process of absorption of the nutrients. The epithelial cells of the villi contain even smaller extensions called 'microvilli'. These microvilli let out digestive enzymes such as sucrase, maltase, and lactase.

These enzymes further break down the carbohydrate molecules, i.e. they break down the disaccharides into monosaccharides. These monosaccharides are then absorbed by the villi, through which they enter the blood capillaries to be transported to other parts of the body.

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 monosaccharides get absorbed into the bloodstream, the blood sugar level of our body rises from its normal level. Soon, the pancreas 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.

The aforementioned digestion process of carbohydrates provides energy to our body to perform various physical and mental activities, breathing, and other significant activities.

Disclaimer: This is for informative purposes only, and should not be used as a replacement for expert medical advice.