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Carbohydrates

Definition

Carbohydrates are one of the main dietary components. This category of foods includes sugars, starches, and fiber.

Alternative Names

Starches; Simple sugars; Sugars; Complex carbohydrates; Diet - carbohydrates; Simple carbohydrates

Function

The primary function of carbohydrates is to provide energy for the body, especially the brain and the nervous system. Your liver breaks down carbohydrates into glucose (blood sugar), which is used for energy by the body.

Food Sources

Carbohydrates are classified as simple or complex. The classification depends on the chemical structure of the particular food source and reflects how quickly the sugar is digested and absorbed. Simple carbohydrates have one (single) or two (double) sugars while complex carbohydrates have three or more.

Examples of single sugars from foods include fructose (found in fruits) and galactose (found in milk products). Double sugars include lactose (found in dairy), maltose (found in certain vegetables and in beer), and sucrose (table sugar). Honey is also a double sugar, but unlike table sugar, contains a small amount of vitamins and minerals. (NOTE: Honey should not be given to children younger than 1 year old.)

Complex carbohydrates, often referred to as "starchy" foods, include:

• Whole grain breads and cereals
• Starchy vegetables
• Legumes

Simple carbohydrates that contain vitamins and minerals occur naturally in:

• Fruits
• Milk and milk products
• Vegetables

Simple carbohydrates are also found in processed and refined sugars such as:

• Candy
• Table sugar
• Syrups (not including natural syrups such as maple)
• Regular (non-diet) carbonated beverages, such as soda

Refined sugars provide calories, but lack vitamins, minerals, and fiber. Such simple sugars are often called "empty calories" and can lead to weight gain. Also, many refined foods, such as white flour, sugar, and polished rice, lack B vitamins and other important nutrients unless they are marked "enriched." It is healthiest to obtain carbohydrates, vitamins, and other nutrients in as natural a form as possible -- for example, from fruit instead of table sugar.

Side Effects

• Excessive carbohydrates can cause an increase in the total caloric intake, causing obesity.
• Deficient carbohydrates can cause a lack of calories (malnutrition), or excessive intake of fats to make up the calories.

Recommendations

For most people, between 40% and 60% of total calories should come from carbohydrates, preferably from complex carbohydrates (starches) and naturally occurring sugars. Complex carbohydrates provide calories, vitamins, minerals, and fiber.

Foods that are high in processed, refined simple sugars provide calories, but they have few nutritional benefits. It is wise to limit such sugars.

To increase complex carbohydrates and healthy nutrients:

• Eat more fruits and vegetables.
• Eat more whole grains, rice, breads, and cereals.
• Eat more legumes (beans, lentils, and dried peas).

Here are recommended serving sizes for foods high in carbohydrates:

• Vegetables: 1 cup of raw vegetables, or 1/2 cup cooked vegetables, or 3/4 cup of vegetable juice
• Fruits: 1 medium size fruit (such as 1 medium apple or 1 medium orange), 1/2 cup of a canned or chopped fruit, or 3/4 cup of fruit juice
• Breads and cereals: 1 slice of bread; 1 ounce or 2/3 cup of ready-to-eat cereal; 1/2 cup of cooked rice, pasta, or cereal; 1/2 cup of cooked dry beans, lentils, or dried peas
• Dairy: 1 cup of skim or lowfat milk

For information about how many servings are recommended see the food guide pyramid.

Here is a sample 2,000 Calorie menu of which 50-60% of the total calories are from carbohydrates.

• Breakfast
  • 1 cup of raspberries
  • 1 1/2 cups of unsweetened cereal, with 1/2 sliced banana
  • 1 cup of skim milk
  • 1 slice of whole wheat toast
  • 1 teaspoon of margarine
  • 1 teaspoon of jelly
  • coffee or tea
• Lunch
  • turkey pita pocket sandwich (2 slices of whole wheat pita bread, 3 ounces of lean turkey breast )
  • 1/2 cup of shredded lettuce
  • 1/2 cup of diced tomatoes
  • 1/2 cup of green peppers
  • 1 tablespoon of salad dressing
  • 1 cup of skim milk
  • 2 fresh, medium-sized peaches
• Dinner
  • 4 ounces of broiled salmon with 3 tablespoons of lemon juice, sprinkled with paprika
  • 1 cup of pasta
  • 1 dinner roll
  • 6 steamed broccoli stalks with black pepper
  • salad:
    • 1 cup lettuce
    • 1/4 cup of sliced mushrooms
    • 1/2 cup of sliced tomatoes
    • 1/2 cup of sliced carrots
    • 1 tablespoon of salad dressing
  • 1/2 cup frozen unsweetened strawberries, sweetened with 1 teaspoon of sugar
  • 1-inch slice of angel food cake
  • 1 cup of skim milk

Review Date:8/15/2006
Reviewed By:Caroline M. Apovian, M.D., FACN, Associate Professor of Medicine, Boston University School of Medicine and Director, Nutrition & Weight Management Center, Boston Medical Center, Boston, MA. Review provided by VeriMed Healthcare Network.

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