Carbohydrates come in three forms: cellulose, starches and sugars. The human body cannot digest cellulose, or fiber, but when it digests starches and sugars it breaks them down into blood glucose, or blood sugar, the body's primary source of energy. The impact of a carbohydrate on the body's blood sugar levels is based not only on the amount of sugars it contains but the types of sugars as well.
Simple and Complex Carbohydrates
There are different types of carbohydrates: simple carbohydrates, consisting of monosaccharides and disaccharides, and complex carbohydrates, consisting of polysaccharides. Monosaccharides are single, simple sugars, like glucose, fructose or galactose. Disaccharides are pairs of monosaccharides linked, or double sugars, such as maltose, lactose and sucrose, or table sugar. Polysaccharides, like starches, are made of ten or more monosaccharides. When any disaccharides or polysaccharides are metabolized in the body, they break down into their constituent simple sugars.
Glucose & Glycemic Load
Glucose is one of the smallest units of carbohydrates. In the bloodstream, where it constitutes about 0.1 percent of the blood, it is called blood sugar. When the body metabolizes glucose through the process of oxidation it produces water, carbon dioxide, oxygen and gives off energy for the cells of the body to use for their activities. The most accurate measure we currently have for determining the amounts and types of sugars a food will break down into is its glycemic load, reflecting both the quantity and quality of carbohydrates it contains. The glycemic index of a carbohydrate compares its blood sugar response in the body following digestion to the blood sugar response of straight glucose. High-glycemic foods tend to yield higher and faster blood sugar increases than low-glycemic index foods.
Energy and Nutrients
Simple carbohydrates provide instant energy but lack nutrients and so can lead to weight gain. Complex carbohydrates provide longer-term energy and supply the body with necessary vitamins and minerals as well. While excessive carbohydrates in the diet can lead to obesity, insufficient carbohydrates can lead to malnutrition. The National Institutes of Health recommends that 40-60 percent of a daily diet be comprised carbohydrates, with the majority in the form of complex carbohydrates.
Fiber
Dietary fiber is the one type of carbohydrate that does not turn into sugar in the body because the body cannot break it down. Instead, fiber helps eliminate waste from the body. Fiber comes in two forms: soluble fiber, as found in nuts, beans and oats; and insoluble fiber, as found in most whole grains and vegetables.
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