Carb Facts

Carbohydrates fuel your body when your metabolism converts them into glucose, a simple form of sugar your cells use for energy. Generally, 40 to 60 percent of your daily calorie intake should come from healthy carbohydrate sources, such as vegetables, fruits and whole grains. Avoid carbohydrate sources that contain few healthy nutrients. For example, refined white sugar provides energy, or calories, but no nutrients.

Sugars

Sugars are simple carbohydrates. Your body quickly breaks them down and converts them to glucose. When you eat foods high in sugar, your blood sugar level rises quickly. In response, your pancreas releases the hormone insulin, which aids in transferring blood sugar to cells. The cells use the glucose they obtain from your bloodstream to fuel your body's activities. Diabetics sometimes have severe reactions to carbohydrates because they lack insulin or their bodies don't use insulin correctly. People with diabetes must control their carbohydrate intake and test their blood sugar frequently to ensure it stays within healthy parameters.

Starches

Starches are complex carbohydrates. Your body converts starches into glucose, like it does sugar, but the digestive process for starches requires two steps. Sugars, in contrast, only require a single digestive action, which takes place in the small intestine where enzymes break sugars down. The first step in the digestion of starches happens in the mouth, where the enzyme salivary amylase begins to break down the starch and convert it to maltose. A similar amylase enzyme in the small intestine completes the conversion. Another type of enzyme in the small intestine then converts the maltose into glucose.

Unhealthy Carbs

Processed foods often contain carbohydrates but few other nutrients, which is why these ingredients are called "unhealthy carbs" or "empty calories." Sugary beverages, for example, provide many calories but do not offer significant nutritional benefits. Cakes, cookies, white bread, pastries and other products that use flour derived from refined grains -- which have their healthy fiber and vitamins removed during processing -- similarly provide many calories without important nutrients. It's best to avoid these relatively unhealthy foods by choosing low-sugar items and opting for whole-grain products, fruits and vegetables whenever possible.

Fiber

Your body can't digest fiber, but it's technically a carbohydrate. Fiber comes in two types, and both promote healthy digestion. Insoluble fiber doesn't dissolve in liquid, but it adds bulk to half-digested food, which helps promote healthy stools. Soluble fiber attracts water to become gelatinous, which helps slow the digestive process. Typical foods that are high in insoluble fiber include wheat bran, vegetables and whole-grain products. Foods high in soluble fiber include legumes, oat bran, barley, peas, seeds and nuts.