Photo Credit Thomas Northcut/Photodisc/Getty Images
The carbohydrates in the foods you eat consist of sugars, starches and fiber, and you get them mostly from plant sources like fruits, vegetables and grains. Sugars and many starches can undergo digestion in your gastrointestinal tract to provide your body with energy, but resistant starches and dietary fiber can’t and, therefore, they don’t add calories to your diet. Whether or not your carbohydrates are digestible, they can all play an important role in your nutrition, and including them in your daily diet can help you maintain optimal health.
Fruits, vegetables and whole grains all contribute carbohydrates to your diet. Your body extracts four calories of energy for each gram of digestible carbs you eat and uses the calories to fuel your physical activities and to maintain your physiological processes. Digestion breaks down sugars and starches to their simplest form so your gut can absorb them into your bloodstream, where they then move to the cells throughout your body. Although your body cannot digest dietary fiber, fiber plays a role in maintaining your digestive health.
The simplest sugars are monosaccharides, such as glucose and fructose. Larger sugar molecules consist of one or more monosaccharides linked together; for example, a glucose bonded to a fructose creates a sucrose molecule. These larger sugar molecules can consist of a variety of monosaccharides, while starch molecules are made up of a large, branched chain of strictly glucose molecules. Your digestive system includes enzymes capable of breaking the bonds linking together the monosaccharides that make up larger sugars and many starches. In this manner, you can digest these types of carbohydrates into simple sugars ready for absorption. A kind of starch called resistant starch is unique in that it is not broken down and travels mostly undigested to your large intestine, where it acts much like fiber. Dried beans, some under-ripe fruits and cooked then cooled starchy foods, such as pasta and rice, are rich in resistant starches.
Dietary fiber is of two types: soluble and insoluble. Your digestive tract cannot break either type into its simpler components; therefore, fiber travels through your gut undigested. Soluble fiber, made of gums or pectins, absorbs water as it passes through your intestines. Because it swells and slows down the absorption of other nutrients, it may help control both blood sugar and cholesterol levels. Insoluble fiber, consisting of lignin, cellulose or hemicellulose, increases the bulk of your stool and helps prevent constipation, although taking in too much can lead to abdominal discomfort. Balancing the amount of each type of fiber you consume every day can improve your digestive health and may help prevent diseases such as colon cancer.
Whether a particular carbohydrate is digestible ultimately depends on your personal physiology. For instance, lactose is made up of one glucose and one galactose molecule. If you lack the digestive enzyme lactase, you are unable to digest this milk sugar, and the presence of lactose in your gut can cause extreme discomfort. In such a case, you can avoid symptoms of pain, gas, bloating and diarrhea by avoiding milk in your diet, drinking lactose-reduced milk or taking lactase supplements.
Article reviewed by Molly Solanki Last updated on: Oct 22, 2012