Many people believe that added fiber has the same health benefits as the fiber naturally found in foods. The fiber that is added to foods is called functional fiber. Functional fiber does not have the same properties as the fiber found in whole grains, fruits and vegetables.
Natural dietary fiber is divided into two categories: soluble and insoluble. The soluble dietary fibers become viscous in water and lowers cholesterol by escorting it out of the body. Lower cholesterol levels help reduce the risk of heart disease and stroke.
Insoluble fibers add stool bulk and promote regularity. Insoluble fiber is not digested in the stomach or small intestine. It gets transported to the large intestine where it has the main effects. Bacteria ferment the fiber causing an increase in the acidity of the large intestine. This increased acidity leads to many health benefits, including a decrease in inflammation, an increase in immune function and increased calcium and mineral uptake. Further, many illness-causing pathogens don't tolerate the acidic environment and die before causing disease. Fiber in the large intestine also helps to add bulk to stool, helping to decrease constipation.
Functional fiber is a non-digestible carbohydrate that has been shown to have some fiber benefits, yet studies are not clear. Similar to soluble fiber, functional fibers are often soluble in water but they are not always 'sticky' and therefore can't lower cholesterol levels the way that soluble fiber can. Functional fiber does seem to increase stool bulk and help decrease constipation.
The basic idea is that while it is okay to get some of your fiber from these added sources, it is not okay to get all of your fiber from added sources. The key is variety, so try to get your fiber from a variety of different sources.
Americans get far too little fiber—about half of what is recommended. We need about 14 grams of fiber per 1,000 calories.
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Contributor: Maude Harris, Nutrition and Health Education Specialist, University of Missouri Extension, firstname.lastname@example.org, 573.545.3516