What You Should Know About Fiber

Tuesday, October 24, 2006 - 2:38pm

By John Messmer, MD

When you look at the nutritional label on prepared foods, you’ll see one line that reads: “dietary fiber.” But what exactly is fiber? In the old days, your mother or grandmother called it “roughage” or “bulk,” but those terms don’t really clear up the confusion for most people. In the end, fiber just doesn’t sound like something you’d want to eat.

Fiber basics and benefits

What is fiber? Simply put, fiber is the part of our food that our bodies can not break down and absorb. A good example of fiber is bran. Bran is an indigestible husk that is removed from grain in order to create refined products, such as white flour and white rice.

When you increase your fiber intake, you subsequently increase your sense of fullness at mealtimes, which in turn leads to the consumption of fewer calories…and results in weight loss. A further benefit of fiber is that it slows the absorption of carbohydrates, which can help control blood sugar levels in diabetics. Also, fiber traps cholesterol, which prevents it from being absorbed in the blood—and thus reduces high blood cholesterol.

Types of fiber

Dietary fiber comes in two varieties: soluble and insoluble. These labels indicate whether the fiber can be dissolved in water. Soluble fiber is often called “gum” fiber because it tends to be gummy when it has dissolved. Soluble fiber is common in fruits and vegetables. Insoluble fiber mostly comes from bran, the covering of the grain as it grows, and is found in whole grains (wheat, rice, barley, corn). It may also be purchased separately or added to foods like boxed cereals.

Effects of poor fiber intake

Fiber’s most important function is to promote the elimination of waste from the intestines. Fiber enables the intestines to squeeze food through the digestive tract. However, if we don’t eat fiber, then everything we eat is absorbed. As a result, there is nothing left for the intestines to squeeze. The immediate result is constipation, which produces a few, small stools. Constipation results in high pressure developing inside the intestines. High pressure can force little pockets called diverticuli to develop. Over time, diverticulosis can cause pain, bleeding and infection, and can lead to surgical removal of part of the intestine.

The typical American eats less than half the recommended dietary fiber. Some authorities think this may be part of the reason for the increase in digestive diseases, some cancers, diabetes, and high cholesterol seen in the last half century. One theory suggests that the chronic inflammation caused by the constant pressure of a low fiber diet could increase the risk of intestinal cancer. That’s because populations that eat lots of fiber tend to have lower rates of intestinal cancer. However this theory has been difficult to test scientifically.

Where to get fiber

When we follow the current dietary guidelines of 5-8 servings of fruits and vegetables daily, it will be easy to get more fiber. Fruit typically has 3-4 grams of fiber per serving. Three dried plums (prunes) provide about 2 grams and three dried figs have over 10 grams. Most berries have lots of fiber—up to 7 grams per cup. Broccoli, carrots, green beans, greens, okra, potato typically have 3-6 grams per cup. Cooked spinach and corn have a bit more. Legumes like peas and the various types of beans can have over 15 grams of fiber per cup. On the other hand, lettuce, cucumber and tomato have very little so a plain salad is not a really good fiber source.

Check the nutrition labels of cereals and you will be surprised to see that your favorite “healthy” cereal may have no significant fiber. Nonetheless, you can still start your day with your favorite if you add some high fiber cereal to it. Then incorporate a variety of fresh or fruits and vegetables into your daily routine for better health.

Fiber supplements

If your diet can not accommodate the variety of foods that provide fiber for whatever reason, fiber supplements are a reasonable alternative. Food is a better source since it supplies important nutrients, but some days we just can’t get what we need. Psyllium seed fiber is available in powder, wafers and capsules. Methylcellulose and polycarbophil from plant fibers are other options.

For further information on how to best include fiber in your healthy diet see the following article from TheDietChannel: What's The Best Source of Fibre: Pills or Food?