Carbohydrates are used by the body as a source of energy, according to National Institutes of Health's MedlinePlus. The digestive system breaks carbohydrates into blood sugar that is needed for energy by the organs, tissues and cells within the body.
Carbohydrates are one of the body's most important fuel sources and a main type of nutrient, according to MedlinePlus. When the body breaks carbohydrates down into sugar for use as energy, it stores any additional unneeded sugar in the muscles and liver for future use.
Carbohydrates can be simple or complex based on their structures, notes MedlinePlus. Everyday foods like milk, milk products, vegetables and fruits contain simple carbohydrates. Simple carbohydrates are also found in sugars that are added to foods when they are refined or processed. Complex carbohydrates are those found in starchy vegetables, legumes, whole grain cereals and breads. Complex carbohydrates are considered to be good sources of fiber in a healthy diet.
The U.S. Food and Drug Administration suggests that adults and children ages 4 and older should have an intake of 300 grams of carbohydrates daily. This intake is fairly easy to meet, since most foods have at least some carbohydrates among their ingredients.
According to the U.S. Centers for Disease Control and Prevention, refined carbohydrates found in cookies, cakes and white bread, are sometimes referred to as bad carbs, while those in whole grain breads, vegetables and beans are known as good carbs.