There are both good and bad carbohydrates. Complex carbohydrates, which contain longer chains of sugar molecules, are generally considered good. Simple carbohydrates are quickly digested and most are considered bad.
Complex carbohydrates digest more slowly than simple carbohydrates, which provide an even release of energy over an extended period of time. Simple carbohydrates cause a spike in energy and blood sugar levels. Complex carbohydrates usually contain high amounts of fiber, while simple carbohydrates often contain high amounts of sugar. Fiber is digested slowly and promotes weight control.
Examples of foods with complex carbohydrate include whole grains, legumes and beans. Foods that contain simple carbohydrates include soda, candy, artificial syrups, pastries, white rice, white bread and white pasta. Fruits and vegetables are simple carbohydrates due to their composition, but their high-fiber content causes digestion similar to complex carbohydrates. Potatoes are the opposite as they are complex carbohydrates but digest like simple carbohydrates. According to the National Academies Institute of Medicine, 45 to 65 percent of the calories in an adult's diet should consist of carbohydrates. In those age 50 or younger, men need at least 38 grams of fiber per day, and women need at least 25 grams per day. After 50, men need at least 30 grams per day, and women need at least 21 grams per day.