Complex carbohydrates are found in plant foods that contain starch and fiber. They are known as polysaccharides, meaning more than two sugars. They come in chains of thousands of glucose molecules.
In order to be absorbed, your body must break apart these molecule chains. It takes considerably more effort for your body to absorb polysaccharides than it does to absorb single or double sugars.
Starch is found in grains, root vegetables, nuts, seeds, and fruits. It can gelatinize, meaning that it gets thick and absorbs water when heated.
Fiber, mainly found in plant cell walls, comes in two varieties; water-soluble, and water insoluble. Both types of fiber are essential for good health.
Water-soluble fiber includes substances like pectin. When water is added, this fiber absorbs it like a sponge and swells. This type of fiber seems to help lower blood cholesterol levels, especially in conjunction with a diet low in fat.
It also tends to delay the emptying of the stomach, so food is absorbed more slowly, causing that full feeling to last longer. Water-soluble fiber is found in beans, some grains, like oats and barley, and fruits and vegetables such as apples and carrots.
Water-insoluble fiber, which includes cellulose, doesn’t swell nearly as much. This includes the structural parts of the plant, like skin, seeds, and stems. Bran, and any whole grain that still includes its outer hull, like brown rice, are great sources of insoluble fiber.
Unlike starch, fiber-based polysaccharides cannot be broken apart by our digestive enzymes. It keeps waste moving through the intestines, which helps prevent disorders of the lower intestine. It is thought that these complex carbohydrates may play a role in the prevention of colon cancer by reducing the time cancer-causing agents spend in the intestine.