Functions of Carbohydrates in Nutrition

The carbohydrates in fruits, vegetables and grains provide essential nutritional functions.
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Carbohydrates, a type of macronutrient, supply calories to your diet. Dietary carbohydrates consist of sugars, starches and fiber. A healthy diet includes between 45 and 65 percent of calories from carbohydrates. For example, a young woman consuming 2,000 calories per day should include 900 to 1,300 calories, or 225 to 325 grams, of carbs in her daily diet. Foods such as fruits, vegetables, legumes and whole grains provide nutritious carbohydrates for your diet.


    The primary role of dietary carbohydrates is to supply fuel to your body; each gram you consume provides 4 calories of energy. All the cells of your body have the ability to convert the carbohydrates you eat into usable energy, and certain organs -- your brain, kidneys and heart, for instance -- require carbohydrates to function effectively. In addition to burning dietary carbohydrates as an energy source, your muscles and liver are able to store a certain amount of carbohydrates for later use. These stored carbohydrates, known as glycogen, serve as a ready fuel source during exercise or at times when your dietary intake is insufficient to cover your energy needs.


    While sugars and starches are digestible by your body, your gastrointestinal tract cannot break down a special type of carbohydrate called fiber, which plays a vital role in your digestive health. By providing bulk to your digestive waste and helping to move it through your intestinal tract, fiber can reduce constipation and hemorrhoids and lower your risk for obesity, colon cancer and cardiovascular disease.

Muscle and Metabolic Health

    When your diet does not contain enough carbohydrates to meet your body’s needs, your body can break down protein and fat and then convert them into the sugar glucose to be used for energy. This conversion comes at a price. Using your body’s protein stores -- that is, your muscles -- to provide glucose for energy can result in loss of muscle mass if your diet consistently lacks sufficient carbohydrates. Breaking down fat stores as a glucose source results in the production of a chemical called ketone bodies. High levels of ketone bodies in your blood -- particularly if they accumulate rapidly -- can cause coma or death. Consuming adequate dietary carbohydrates helps maintain your muscle mass and metabolic health.

Other Functions

    Carbohydrates help maintain optimal physiology of your cellular components. Certain proteins in your cells undergo a process called glycosylation in which carbohydrate molecules attach to them, and it is only in the glycosylated state that the proteins are functional. The carbohydrate ribose is an integral component of the nucleic acids RNA and DNA. These nucleic acids provide the genetic material found in all the cells of your body.

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