Digestion begins in your mouth and continues as food passes down into your stomach and moves into your intestines. The intestines are a critical part of your digestive system because they absorb nutrients from food and prepare it for elimination from the body as stool. Foods with fiber aid in the digestive process because of how they are handled in the intestines.
Definition
Fiber is a component of food your intestines cannot absorb. Proteins, carbohydrates and fats are readily absorbed, but fiber moves through your entire digestive system, including the intestines, and passes out of your body almost intact. Fiber is also called dietary bulk or roughage, and the substance comes from indigestible parts of plant-based foods.
Types
Dietary bulk that does not get absorbed in the intestines comes in two types, known as insoluble fiber and soluble fiber. Soluble fiber changes its form to a gel-like substance as it moves through the body because it is soluble in water. Insoluble fiber remains in its original form because it is unaffected by water encountered during the digestive process.
Sources
Fiber occurs naturally in many plant-based foods, and you can purchase fiber supplements. Soluble fiber comes from apples, oats, peas, carrots, beans, citrus fruits, psyllium and barley. Insoluble fiber is in vegetables, nuts, wheat bran and whole-wheat flour. Refined foods contain little or no fiber, MayoClinic.com notes, and you get more benefits from eating a high-fiber diet than by using supplements.
Benefits
Foods that cannot be absorbed by the intestines have health benefits. Insoluble fiber prevents constipation because it helps move other food through the intestines as it moves through unchanged. This fiber also adds bulk to stool. Soluble fiber reduces cholesterol levels, lowers blood pressure, and stabilizes blood sugar levels. Fiber helps you feel full on less food because of its bulk, so fiber-rich foods are beneficial for weight loss. Fiber also helps prevent diabetes and diverticular disease.
Amount
Women should get more than 20 g of fiber per day, while men should get more than 30 g, the Harvard School of Public Health advises. Fiber needs are usually met by a well-rounded diet that includes a lot of fruit, vegetables, beans and whole grains. Add dietary fiber by eating whole-grain breakfast cereals, eating fruit and raw vegetables as snacks, replacing white bread and other processed foods with whole-grain alternatives and replacing meat with beans.
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