All living beings need energy in order to function. Carbohydrates, fats, and proteins, in any reasonable combination, are the sources of energy, or fuel, for the human body.
Despite their importance to the body as the dominant source of energy, foods rich in carbohydrates are regarded by many people in our society as inferior. Yet they are enjoyable to eat and are the most economical of all nutrients to produce, to store, and to buy. With the high cost of meat and other protein foods, money-saving carbohydrate foods will probably continue to gain in popularity. Most nutrition scientists agree that the 12 percent of daily calories obtained by Americans from protein is about the right amount but that the 42 percent obtained from fat should perhaps drop toward 30 to 35 percent, and the 46 percent obtained from carbohydrates should increase. They suggest including more complex carbohydrates in the diet while reducing refined sugar intake.
To many people, the word “carbohydrate” is synonymous with certain foods: bread, rice, potatoes, or spaghetti, for example. However, no one food is a source of a single nutrient. Also, carbohydrates are present in varying amounts in many foods, including fruits, vegetables, and some dairy products. The sugars, starches, pectins, cellulose, and glycogen in foods are all carbohydrates.
It is important to learn about high-carbohydrate foods – those containing large amounts of sugars and starches that can be broken down in the body into glucose. Sugars are in foods such as table sugar, honey, jam, jelly, syrup, and fruits. Starches are a major component of cereals, flour, potatoes, beans, squash, and other vegetables.
Glucose is a simple sugar, the main one known to exist in a pure state in the body during fasting, and the body’s preferred source of energy. The carbohydrates found in most of our foods are broken down during digestion to release glucose for fuel. This fuel supplies the energy specifically needed for the operation of the brain and nervous system as well as the energy for physical activity and the inner workings of the body such as tissue building and repair and the absorption and transport of nutrients.