Mark White, age 13, of Peoria, Ill., for his question:

WHERE DOES SUGAR COME FROM?

Records show that sugar was a well known food item at the    time of Alexander the Great. Many mentions of sugar are found in the Bible, too. The Moors had sugar cane with them when they moved into Spain in the 700s A.D. By the 900s the

Venetians brought sugar to Venice from the Tigres and Euphrates valleys and also from Egypt and Syria. Sugar has been around for a long time. Now it is one of our most important foods. Sugar supplies energy and heat for the body, much as gasoline gives power and heat for an automobile.    But, of course, we shouldn't eat too much of it.

Most of the commercial sugar used today comes from one of two sources: sugar beets or sugar cane. Lesser amounts come from maple trees, cornstarch and even milk.

Sugar cane can be found in most tropical or subtropical climates. Sugar beets grow in temperate zones. When the sugar is purified or refined, there is absolutely no difference in the chemical composition of the sugar obtained from either of these plants.

Actually, almost all plants manufacture sugar. All of the plants on earth, scientists tell us, make about 400 billion tons of sugar every year. About 80 percent of the food energy of fruits comes from their sugar content. And sugar is also found in such familiar foods as spinach, nuts, onions and carrots.

The type of sugar found in most plants is called sucrose, and it comes from the stems and leaves. Honey and sweet fruits such as grapes are made up of other types of sugar called glucose and fructose.