by Dasa Suciu

Created on: June 21, 2009   Last Updated: June 23, 2009

Dietary fiber, known also as roughage, is plant material that is not digested by the enzymes of the digestive system. Not being digestible, it has neither nutritional nor energy value. Although it cannot be digested, our bodies need roughage because the bulky substance cleans the colon as it makes its way through our digestive tract. There are two main types of fiber: soluble and insoluble. Dietary fiber comes from vegetables, fruit and grain. These contain both soluble and insoluble fiber in various quantities.

Soluble Fiber

Soluble fiber has some important functions in our diet: it controls the assimilation of sugars and fats, regulating the amount of sugar and reducing bad cholesterol in the blood. Soluble fiber changes as it goes through the digestive tract, where it is fermented by bacteria. Soluble fiber, such as pectin, gum and mucilage, absorbs water, and during digestion it transforms into a gel. Inulin, for example, facilitates the assimilation of calcium and feeds good bacteria in the colon, bacteria which produce cancer fighting fatty acids. Lignin prevents the absorption of fat. Pectin, limiting the uptake of glucose and causing a reduction in the need for insulin, is ideal in preventing senile diabetes.

Examples of soluble fiber are many vegetables, barley, oats, rye, and fruits like peaches, grapes, prunes, berries, and pears. Oat bran has the highest proportion of soluble fiber among cereals, about 14% soluble fiber.

Insoluble Fiber

On the contrary, insoluble fiber, which does not dissolve in water, goes through the digestive tract without changing its form. It is composed of cellulose, hemicellulose and lignin and is found mainly in cereals and vegetables. Insoluble fibers have some important functions in our diet: it promotes regular bowel movements through the digestive tract, and controls pH levels in the intestines. By reducing the time harmful substances stay in contact with the bowel wall, and keeping an optimal acidity in the intestines, insoluble fiber helps the elimination of toxic waste through the colon. Less long food remains in the intestine, the lower the risk of the emergence of disorders such as hemorrhoids, constipation and colorectal cancer.

Examples of insoluble fiber are whole grains, pasta, beans, brown rice, nuts, seeds, bran, and root vegetables like carrots and celery. It's important to eat the skin of fruits like apples, since that is where most of the fiber resides.

Recommendations

The maximum daily intake recommended by dieticians

• 1
• 2
• Next Page >>