Carbohydrates are compounds of carbon, hydrogen, and oxygen, linked by energy-containing bonds. Carbohydrates can be divided into two groups: simple and complex. Simple carbohydrates are otherwise known as sugars and are classified according to the number of sugar molecules they have: monosaccharides (1 sugar molecule) or disaccharides (2 sugar molecules). Complex carbohydrates, such as cellulose and starch, are called polysaccharides.
Carbohydrates are broken down into glucose, which is the main source of “fuel” for the human body – it gives the body’s tissues and cells energy. The process goes as follows:
1. Upon eating the food, the digestion of carbohydrates begins. The first step happens in the mouth, where an enzyme found in saliva disintegrates starch molecules into maltose, which is a disaccharide. 2. In the small intestine, a pancreatic enzyme is used to further disintegrate starch into disaccharides and smaller polysaccharides. 3. Cells found in the small intestine release an enzyme, which breaks down disaccharides and polysaccharides into monosaccharides. 4. These same cells absorb the monosaccharides and take them to the liver, where they are turned into glucose, or, if there is an excess of fructose and galactose (monosaccharides), they may be turned into fat. 5. The glucose is transported to the cells, where it is used to obtain energy.
If there is an excess of glucose, the muscles and liver convert it to glycogen – a storage form of glucose. The muscles store more than half of the glucogen and the rest is stored in the liver. Glucogen is turned into glucose and used for energy whenever blood glucose levels decline.
Fiber is a polysaccharide, which cannot be digested by human beings, and it comes in two forms 1) water-soluble and 2) water-insoluble. Despite the fact that fiber cannot be digested, it has it’s uses: water-insoluble fiber can be found in whole grain, nuts, seeds,etc., it binds bile acids, thus lessening the absorbtion of fat and cholesterol; water-soluble fiber is found in fruit, barley, legumes, oats, etc., it decreases “bad cholesterol” (low-density lipo-protein).
One of the complex carbohydrates, fiber, is a pol-ysaccharide in which the bonds holding it together cannot be digested by humans. Fiber can be either water-soluble or water-insoluble. Even though these compounds cannot be digested by humans, they serve several important functions. The main function of insoluble fiber is to bind bile acids, which reduces fat and cholesterol absorption. Sources of insoluble fiber include wheat bran, whole grains, and brown rice. Soluble fiber, which helps decrease low-density lipo-protein (LDL) cholesterol, also called the “bad” cholesterol, can be found in barley, fruit, legumes, and oats.
Fiber is extremely important, because it helps control weight by removing calorie-dense fats in the diet. Fiber promotes a feeling of fullness by absorbing water and thus slowing down the movement of food through the digestive tract. It is recommended to take about 27 to 40 grams of fiber per day.
It is recommended that 45–65% of total calories should come from carbohydrates, also, foods containing polysaccharides should be preferred over foods containing disaccharides and monosaccharides.
The intake of carbohydrates should not be ignored, because if it is low, there is not enough glucose, thus making the body use protein instead, which leads to the inability of protein to fulfil other functions, such as maintaining the immune system.