Fiber / What is Fiber?

Types of Dietary Fiber: Water Soluble Fiber; Soluble Fiber; Water Insoluble Fiber; Insoluble Fiber; Pectins; Gums; Mucilages

What it is: Given all the media hype about fiber, you'd assume it was a vital NUTRIENT. You'd be wrong. Although classified as a CARBOHYDRATE, fiber supplies no VITAMINS, MINERALS or even CALORIES. It does, however, play important roles in the body. Basically, there are two types of fibers: those that dissolve in water (water-soluble or, more simply, soluble fiber) and those that don't (water-insoluble or insoluble fiber). The water-soluble fibers - PECTINS, GUMSand mucilages — are found mainly in citrus fruits, apples, potatoes, dried peas and beans, oatmeal and oat BRAN. In the body, they bind bile acids (the liver synthesizes these out of CHOLESTEROL), and as the acids are bound, cholesterol is withdrawn from the blood and converted to bile acids to replace the deficit. The cholesterol-lowering effect may be subtle; still, it reduces the risk of heart disease. Water-soluble fiber also lowers — or at least stabilizes — blood sugar GLUCOSE) levels. And that's good news for diabetics. Intricately bound to digestible carbohydrates, which the body breaks down to form glucose, fiber acts like a brake, slowing the digestion of carbohydrates and subsequent release of glucose into the blood.

The two most common water-insoluble fibers, CELLULOSE and lignin, form the framework of plant cell walls. Neither cellulose (found in wheat bran, whole wheat, whole-grain breakfast cereals, broccoli and carrots) nor lignin (asparagus, wheat bran and pears) will dissolve in water, but both have the ability to absorb it. This means they bulk up stools and speed the passage of waste through the intestines, functions believed to reduce the risk of colon cancer.

If you haven't been eating enough fiber, it's wise to increase your intake slowly. Doing so all at once can cause gas, bloating, diarrhea. It's also important to drink plenty of water when eating lots of fiber. Otherwise, you may irritate, even block your digestive tract.

So how much fiber is enough? There is no RDA for fiber, but most nutritionists recommend 20 to 35 grams of fiber a day (most Americans get no more than 10 to 13 grams). They also recommend that you include both the water-soluble and water-insoluble fiber in your diet. No problem if you regularly eat a wide variety of fruits, vegetables and whole-grain breads and cereals.

Note: Many grains, brans, fruits and vegetables contain both types of fiber. But no animal food (meat, eggs, milk, cheese, etc.) provides any fiber whatsoever.

Some of this information from THE NUTRITION BIBLE, Jean Anderson and Barbara Deskins. Copyright © 1995 by Jean Anderson and Barbara Deskins.