Two type of starches exist, according to the National Starch Food Innovation -- starches that are digested in the small intestines and resistant starch, which is processed in the lower intestine. In the colon, resistant starch is broken down and may have the ability to increase healthy bowel functioning. Some foods exist that naturally contain resistant starch. These foods are classified from RS1 to RS3. RS4 denotes chemically changed starches that are not found naturally.
Beans
Resistant starch is a third type of fiber that is neither soluble or insoluble. Beans and legumes are a source of this fiber, carrying an RS1 classification. The Commonwealth Scientific and Industrial Research Organisation of Australia says that some legumes may have as much as 10 percent resistant starch content. Beans that fit into the RS1 category may include kidney, split pea, soy, black-eyed peas, lentils, fava, pinto, lima, mung, calico, navy and Italian beans.
Cooked and Chilled
Some foods' resistant starch content is increased by chilling. Cooling the food allows resistant starch crystals to form, which the small intestine cannot process. The small intestine is where most of the absorption of nutrients take place. Three major foods fit into this category and have an RS3 classification. They are cooked and chilled potatoes, pasta and rice.
Whole Grains and Other Foods
Unprocessed whole grains and seeds are graded as RS1. Harvard Medical School includes barley, bulgur or cracked wheat, amaranth, oats, quinoa, flaxseed, rye, millet and spelt as whole grains. Other foods that are high in resistant starch and have a RS2 rating are moderately green bananas, uncooked potatoes and high amylose corn. High amylose corn is a hybrid that is used to make high amylose cornstarch.
