What Are Complex & Simple Sugars?

When you hear the word sugar, the first thing that may come to mind is the sweet-tasting white crystalline granules that you find in your pantry or on your table. This type of sugar is a simple sugar called sucrose, or table sugar. Complex sugars are those found in the whole grains, fruits, vegetables and legumes of your diet.


Complex and simple sugars are carbohydrates -- compounds made of carbon, hydrogen and oxygen. Both types of sugars provide energy to your body's cells. However, your body must first break down carbohydrates into glucose for your body to utilize the carbohydrates for energy. Carbohydrate break down into glucose occurs during the process of digestion.

Types of Sugars

A simple sugar containing a single molecule is called a monosaccharide. The most common monosaccharide is glucose -- an important source of energy for your brain cells. Other monosaccharides include galactose found in milk and fructose found in fruit.

A simple sugar containing two monosaccharide molecules is called a disaccharide. Lactose, or milk sugar, is composed of glucose plus galactose. Sucrose is a disaccharide composed of glucose plus fructose. Your small intestine digests the disaccharides into monosaccharides during absorption.

Complex sugars are generally composed of long chains of glucose molecules and various other simple sugars. Examples are the starches and types of dietary fiber that are found in plant foods.


You may obtain simple sugars such as lactose and fructose naturally through milk, milk products, fruits and vegetables. A simple sugar such as sucrose may be found in processed foods, candies, beverages and syrups. Natural sources of complex sugars include legumes, starchy vegetables and whole grain breads and cereals. Processed foods such as white flour and polished rice also contain starchy complex sugars.


Too much sugar of any kind can produce weight gain, and too much of a simple sugar like sucrose may lead to dental caries. Your body digests complex sugars into glucose more slowly than simple sugars. Therefore, complex sugars, especially those that also contain dietary fiber, tend to raise your blood glucose level more slowly and are recommended for people with diabetes.


Based on the role of glucose as the primary energy source for your brain, the recommended dietary allowance for total digestible carbohydrate is 130 grams per day for adult women, 175 grams per day during pregnancy and 210 grams per day during lactation. The recommended intake of total dietary fiber is 25 to 29 grams per day. At least half of your total intake of grains should be as whole grain foods, according to the USDA's Dietary Guidelines for Americans. The Guidelines also recommend that you limit your intake of processed foods that contain added sugars such as sucrose and high fructose corn syrup.


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