Simple sugars make foods sweet. They are small molecules found in many foods and in many forms. Some simple sugars occur naturally in foods. For example, fructose is the sugar that naturally gives some fruits their sweet flavor.

Table sugar, the sugar that we spoon onto our cereal and add to the cookies we bake, also called sucrose, is the most familiar simple sugar. A ring-shaped molecule of sucrose actually consists of a molecule of fructose chemically linked to a molecule of another simple sugar called glucose.

Sugars such as fructose and glucose are known as monosaccharides, because of their single (mono) ring structure, whereas two-ringed sugars such as sucrose are known as disaccharides. Another disaccharide, lactose, the sugar that gives milk its slightly sweet taste, consists of glucose linked to yet another simple sugar called galactose.

The inability to digest lactose to its constituent sugars is the cause of lactose intolerance, a condition common to adults of Asian, Mediterranean, and African ancestry. The table sugar that we purchase is processed from sugar cane or sugar beets.

As an additive to many different types of prepared or processed foods, sucrose adds nutritive value (in the form of calories only), flavor, texture, and structure, while helping to retain moisture. Today, sucrose is most often used to sweeten (nondietetic) carbonated beverages and fruit drinks (other than juice), candy, pastries, cakes, cookies, and frozen desserts.

One of the most commonly consumed forms of sugar is called high-fructose corn syrup. High-fructose corn syrup is also commonly used to sweeten sodas, fruit drinks (not juices), some ice creams, and some manufactured pastries and cookies. Other forms of sucrose include brown sugar, maple syrup, molasses, and turbinado (raw) sugar.

Foods that are high in added sugar are often low in essential nutrients such as vitamins and minerals. Unfortunately, these foods are often eaten in place of more nutrient-rich foods such as fruits, vegetables, and low-fat whole-grain products, and they may prevent us from obtaining essential nutrients and lead to weight gain.

Nutritionists are concerned by the enormous increase in sugar consumption by Americans during the past 30 years, particularly because much of this sugar is in the form of soft drinks. On average, teens today drink twice as much soda as milk, and young adults drink three times as much soda as milk.

As a result, their intake of calcium-rich foods is low, a factor that is thought to contribute to lower bone mass. This can lead to an increased risk of bone problems as we grow older. The increase in sugar consumption also has been attributed to the increasing availability of low-fat versions of such dessert and snack foods as cookies, cakes, and frozen desserts.

Often, the sugar content of these foods is high because sugar is used to replace the flavor lost when the fat is decreased. Sugar promotes tooth decay, when consumed in forms that allow it to remain in contact with the teeth for extended periods. Thus, foods that are high in sugar, or sugar and fat, and have few other nutrients to offer appear at the top of the Food Guide Pyramid because they should be eaten sparingly.

In contrast, choosing fresh fruits, which are naturally sweetened with their own fructose, or low-fat yogurt, which contains lactose (natural milk sugar), allows us to get the vitamins and minerals contained in those foods as well as other food components that contribute to health but may not have yet been identified.

On the positive side, there is no credible evidence to demonstrate that sugar causes diabetes, attention deficit-hyperactivity disorder, depression, or hypoglycemia. No evidence has been found that sugar-containing foods are “addictive” in the true sense of the word, although many people report craving sweet foods, particularly those that are also high in fat.