Nutrition and You: Fascinating, Fabulous Fiber

Laura E. Matarese, PhD, RD, LDN, FADA, CNSD

Fiber is indeed fascinating and fabulous, and it’s an important aspect of nutritional care for those with intestinal failure. There are different types of fiber. Some are well tolerated by individuals with intestinal failure and others may present a problem. Basically, fiber can be classified into three categories: soluble, insoluble, and functional.

Soluble Fibers

Soluble fibers are very important to people with short bowel syndrome (SBS), particularly if the colon is connected. These fibers dissolve in water (are soluble) and form a gelatinous substance (like Jell-O) when combined with water. Soluble fibers slow transit time (the time it takes for something to go through your gastrointestinal tract), which may help with absorption of nutrients. They also add bulk, which helps to solidify bowel movements and gelatinize ostomy output. This may give you a little more control over your output. The added bulk also increases the satiety value of the diet.

Soluble fibers also help to balance intestinal pH and, as they ferment, they stimulate intestinal production of short-chain fatty acids (SCFA). These SCFA are then absorbed through the mucosa (lining) of the colon and used as a source of energy. The SCFA also help with sodium and water absorption. SCFA also have a nutritional effect on the number and quality of cells in the gastrointestinal tract and stimulate intestinal adaptation.

You can get soluble fiber naturally through food, such as legumes (peas, soybeans, and other beans), oats, rye, barley, some fruits and fruit juices (including prune juice, plums, berries, bananas, and the insides of apples and pears), certain vegetables (including broccoli, carrots, and Jerusalem artichokes), root vegetables (sweet potatoes, onions, and potato skins are sources of soluble fiber), and psyllium seed husk (a mucilage soluble fiber; mucilage is a thick gluey substance, similar in texture to marshmallows, produced by most plants).

Insoluble Fibers

Insoluble fibers pass through the gastrointestinal track largely unchanged. Nonetheless they do have an effect. They increase bulk, soften stool, increase satiety value of the diet, and help to control and balance intestinal pH. They also shorten transit time, which is why many individuals with SBS often do not tolerate insoluble fiber.

Food sources of insoluble fiber include whole grain foods, wheat and corn bran, nuts and seeds, potato skins, flax seed, sesame seed, and vegetables such as green beans, cauliflower, zucchini, and celery. Insoluble fiber may also be found in the skins of some fruits, including tomatoes. That is why many HPEN consumers with SBS often benefit from peeling fruit before eating.

Functional Fibers

The category “functional fibers” is a new category. Functional fibers are non-digestible carbohydrates engineered or extracted from plants. They add bulk to food, increase fiber without grit, and improve the mouth feel, stability, and taste of food. In animal studies, functional fibers have been shown to confer the health benefits of soluble fiber. However, they do not provide other nutrients found in whole foods. For example, if you eat a banana, you not only get the soluble fiber but you also get nutrients such as potassium.

Examples of engineered functional fibers include polydextrose from dextrose, sorbitol, and citric acid. Extracted functional fibers include pectin from citrus and cellulose from trees, as well as natural polydextrins from inulin and oligofructose extracted from chicory root.

Getting Fiber

Food is best. Remember that when introducing a new food into your diet, you should start with small amounts and gradually increase the amounts. If you cannot eat enough fiber-containing foods, there are fiber supplements (see Sept/Oct 2008 LifelineLetter). These are generally soluble fiber.