What Are the Characteristics of Carbohydrates?

Carbohydrates are one of three macronutrients, besides protein and fat, that you need in fairly large quantities to maintain your life and important body functions. They are revered for their ability to energize you quickly but also blamed for thickening waistlines in the rise of so-called low-carb diets. Nutritionists and public health officials still encourage you to get most of your calories from this nutrient, so it's important to learn to identify high-quality, healthy carbohydrates.

A close-up of dry pasta nests. (Image: Nanisimova/iStock/Getty Images)

Chemical Structure

A carbohydrate is a simple sugar. Its basic structure is composed of the elements carbon, hydrogen and oxygen, with generally twice the hydrogen as carbon and oxygen. In its simplest form, a carbohydrate is a chain of sugar molecules called monosaccharides. When these simple sugars are combined, you get disaccharides, oligosaccharides and polysaccharides.

Major Food Forms of Carbohydrates

In your diet, you can eat simple carbs or complex carbs. Simple carbs include sugars found naturally in foods like fruits, vegetables, milk and products made from milk. You'll also add a lot of simple carbs to your diet if you eat processed foods and soft drinks. Complex carbs are found in whole-grain foods like breads and cereals. You'll also find them in starchy vegetables and legumes, like beans. Fiber is an important type of carbohydrate found in plant foods. Fiber helps regulate your bowel function, lowers your risk of developing hemorrhoids and colon pouches, lowers your cholesterol and helps control your blood sugar. Carbohydrates provide 4 calories per gram.

Functions

Carbs are your body's main source of fuel. They are most easily converted to glucose, which is used by your cells for energy. All your body's systems and organs need glucose to function properly. Carbs also spare your muscle when your body goes looking for energy. If you eat a low-carb diet, your body will turn to fat tissue next, but then will begin to use your muscle if it must. Your body can store up to 400 g carbs as glycogen for later use, but if you give it more than your body needs or can store, those extra carbs can be converted to store as fat.

Glycemic Index

All carbs are not made the same. When carbs are detached from fiber, they process rather quickly, causing a rapid increase in your blood sugar and insulin levels. Carbs that do this are called high glycemic. High-glycemic diets are associated with diabetes and obesity. Complex carbs tend to be low glycemic, keep your blood sugar relatively stable and digest more slowly. The glycemic index categorizes carbs based on their effect on blood sugar, relative to a simple sugar. A food scoring higher than 70 is considered high glycemic.

Daily Reference Intake

The Institute of Medicine recommends that 45 to 65 percent of your daily calories come from carbohydrates. You need between 20 and 35 grams of fiber. It's important to choose your carbs wisely, however. Carbs from processed foods tend to come with extra calories that will make controlling your weight more difficult. It recommends you get most of your carbs from the basic food groups, including fruit, vegetables and whole grains.