One advantage of a high starch diet is that it will almost automatically be high in fiber unless the foods are refined or highly processed.
Fiber (formerly called roughage) is a general term that refers to the substances in food resistant digestion. The amount of fiber in a food is determined by its plant source and the amount of processing it undergoes. In general the more a food is processed, the more the fiber is broken down or removed and the lower the fiber content.
The fiber content shown on food labels is usually listed as either dietary fiber or crude fiber. Dietary fiber is the actual residual of plant food that resists digestion in the human body. Crude fiber is the residue of plant food following a harsh chemical digestive procedure in the laboratory; 1 gram of crude fiber equals 2 to 3 grams of dietary fiber.
There are two kinds of fiber: soluble fiber, which dissolves or swells in hot water, and insoluble fiber, which does not dissolve in water. Each plant food usually contains a mixture of fiber types.
Soluble fiber appears to have several favorable effects. Because it forms gel in water, it adds bulk and thickness to the contents of the stomach and may slow emptying, thus prolonging the sense of fullness and possibly helping dieters control their appetites. Studies have shown that soluble fiber lowers blood cholesterol levels. The results of 10 studies reported in the journal of the American medical association 40 showed that eating oat bran cereal or oatmeal every day can lower blood cholesterol by an average of 2% to 3%. Diets high in carbohydrates and fiber, especially soluble fiber, improve blood glucose control, lower insulin requirements, and reduce blood cholesterol and blood pressure in people with diabetes. Soluble fiber also slows the absorption of sugars from the small intestine, another benefit for those with diabetes.
Good sources of soluble fiber are fruits, vegetables, and grains. Specific foods include prunes, pears, oranges, apples, dried beans, cauliflower, zucchini, sweet potatoes, and oat and corn bran.
Insoluble fiber adds bulk to the contents of the intestine. This speeds the transit time of a meal's remnants through the small and large intestines. This in turn appears to offer the important health benefits.