Carbohydrates, which include sugars, are a source of fuel for the body. Carbohydrates are broken down by the digestive tract to form energy, but different types of carbohydrates provide energy at different rates. A healthy and well-balanced diet contains different carbohydrate sources in the right proportions.
Calories in Carbohydrates
The energy that carbohydrates provide for the body can be measured in terms of calories. Every gram of carbohydrate that you consume provides four calories for your body. Most dietary programs recommend that between 45 and 65 percent of calories be from from carbohydrates. This means that, if you are following a 2,000 calorie per day diet, between 900 and 1,300 of your calories would come from carbohydrates. This amounts to between 225 and 325 g of carbohydrates each day.
Types of Carbohydrates
There are two main kinds of carbohydrates: simple and complex. Simple carbohydrates, which include sugars, consist of one or two carbohydrate molecules. There are many different kinds of sugar, including glucose, fructose, lactose and sucrose. Complex carbohydrates, on the other hand, are made up of many carbohydrate molecules that have been linked together. Starch is the main complex carbohydrate found in plants. Animals can store many different carbohydrate molecules in the form of glycogen, which is made by the liver.
How The Body Uses Carbohydrates
The most important nutritional role that carbohydrates play is as a source of fuel in the form of blood glucose. When you consume foods with carbohydrates, your digestive tract breaks them down into simple sugars with the help of special proteins known as enzymes. Once the carbohydrates have been broken down into sugars, they are absorbed and converted into glucose, which is a sugar that the body uses for energy, for distribution to the body's cells by the liver. An increase in blood glucose levels causes the body to secrete insulin, a hormone that prompts muscle and fat cells to pick up excess glucose to use as energy or to store as fat.
"Good" and "Bad" Carbohydrates
As a general rule, "bad" carbohydrates are refined carbohydrates, such as those that come from added sugars and processed grains, including white flour. Consuming "bad" carbohydrates causes your blood glucose levels to increase sharply, followed by a spike in insulin, which quickly processes the sugar and causes you to feel hungry again shortly thereafter. "Good" carbohydrates come in the form of vegetables, fruits and whole grains. These carbohydrates are broken down more slowly by your digestive tract, resulting in a more gradual release of energy and slower insulin response. "Good" carbohydrates are also rich in important vitamins, minerals and fiber, which are all important substances for a healthy diet.
Micronutrients
Many kinds of carbohydrates also provide fiber, a type of carbohydrate that is not broken down by the digestive tract and helps maintain the health of your digestive tract. Whole grains, vegetables and fruits are all carbohydrate sources that provide fiber. These foods also provide important vitamins and minerals, though the vitamin and mineral content of carbohydrate sources varies from food to food. For example, whole wheat bread contains significant amounts of iron, riboflavin, niacin, thiamine, potassium, folate and vitamin E, while ice cream, though full of carbs, contains very little of these nutrients.
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