Dietary fiber is the undigested plant residue that passes through the intestinal tract. Just as there are many types of plants, there are also types of fiber. Fiber may be soluble (oat bran, psyllium) and form a gelatinous bulk which has cholesterol-lowering properties. Or it may be insoluble (wheat and other grains) which adds bulk to the stool. Both are important and provide benefits.

The Function of the Large Intestine

The principal function of the large intestine (colon) is to complete digestion by removing excess water from food wastes passing into it from the small intestine too quickly, not enough water is absorbed and diarrhea results. In contrast, if waste material is passed to slowly, too much water is absorbed. This results in hard stool and constipation, often leading to straining.

The Importance of Dietary Fiber

Fiber, also called roughage or bulk, is necessary to promote the wavelike contractions that move food through the intestine. High fiber foods expand the inside walls of the colon, easing the passage of waste. As fiber passes through the intestine undigested, it absorbs many times it weight in water, resulting in softer and bulkier stools. Studies have shown that rural Africans, whose diets are rich in fiber, eliminate food waste in one-third the time it takes urban, Westernized people to do so, and have larger and softer stools. Because of this greater bulk and faster transit time (the time required to digest food and expel wastes), it is believed that harmful substances are also swept out before they can cause problems. In fact, these rural people suffer less from many of the digestive tract diseases that plague Western man, and it is thought that this may be related to the nature of their diet. A high fiber diet causes a large, soft, bulky stool that passes through the bowel easily and quickly. Because of this elimination-easing action, some digestive tract disorders may be avoided, halted or even reversed. A softer, larger stool helps prevent constipation and straining, which can help avoid or relieve hemorrhoids. More bulk means less pressure in the colon, and this is important in treating irritable bowel syndrome and diverticulosis.

Most Americans eat 10 to 15 grams of fiber a day, whereas 20 to 35 grams are recommended. High fiber foods, such as fruits and vegetables, also tend to be low in calories, so weight gain should not be a problem. Fiber pills generally should not be taken as they contain relatively little fiber and are expensive compared to fiber-containing foods and powder supplements.

A Dietary Fiber Supplement May Be Helpful

Some people don’t tolerate excessive fibrous foods well. Stool softening and bulking agents are available. These products are plant fiber that absorb water and produce the bulk necessary for the digestive tract to perform naturally. Psyllium fiber is found in many commercial products such as Metamucil, Per Diem and Konsyl. The regular product contains a fair amount of sugar, so it may be preferable to use the sugar-free substitutes. Most pharmacies carry a generic brand at significant cost savings. Citrucel (hemicelulose) and Equilactin (polycarboxisal) are other bulking agents that can be used. These fiber supplements, in conjunction with foods, are a readily available way to reach the fiber goal of 20 to 35 grams per day.

Fiber Content of Foods

Goal —20 to 35 grams per day

Common servings of foods containing dietary fiber are shown below. A variety of foods should e chosen every day. Foods that are good sources of fiber are typically low in fat and calories.

1 medium bran muffin 3
1 slice whole wheat bread 2
1 slice white bread 1
1 slice pumpernickel bread 1
1 slice rye bread 1
1 slice raisin bread < 1
1 slice saltines 0
1 ounce Kellogg’s All-Bran Extra Fiber 14
1 ounce General Mills Fiber One 12
1 ounce Kellogg’s All-Bran 9
1 cup whole wheat pasta 5
1 ounce Kellogg’s Bran Flakes 4
1 ounce Post Fruit and Fiber 4
1.4 ounces Kellogg’s Raisin Bran 4
1 ounce Nabisco Shredded Wheat’n Bran 4
1 ounce oatbran 4
1 ounce General Mills Raisin Nut Bran 3
1 ounce General Mills Cheerios 2
1 ounce Post Grape-Nuts 2
1 ounce oatmeal 2
1 cup popcorn 2
1 ounce General Mills Total 2
1 ounce General Mills Wheaties 2
1 cup pasta <1
1 ounce Kellogg’s Corn Flakes <1
1/2 cup cooked brown rice <1
1/2 cup cooked white rice <1
1/2 cup egg noodles 0
1/2 cup kidney beans 9
1/2 cup baked beans 7
1/2 cup navy beans 5
1/2 cup pinto beans 5
1/2 cup lentils 2
1/2 cup cooked frozen peas 4
1 medium baked potato (with skin) 4
1/2 cup cooked broccoli tops 3
1/2 cup cooked young carrots 3
1/2 cup cooked corn 3
1/2 medium fresh avocado 2
1/2 cup cooked green beans 2
1/2 cup brussels sprouts 2
1/2 cup cooked eggplant 2
1/2 medium cooked sweet potato 2
1/2 cup raw cabbage 2
1/2 cup raw bean sprouts 1
1/2 cup raw lettuce 1
1/2 cup sliced raw mushrooms 1
1 medium dill pickle 1
1/2 cup mashed potatoes 1
10 medium french fried potatoes 1
half fresh tomato 1
1 stalk raw celery <1
6 slices raw cucumber <1
2 rings green pepper <1
1/2 cup raw onions <1
3.5 ounces dried figs 18
3.5 ounces prunces 8
3.5 ounces raspberries 7
1/4 cup almonds 5
1 medium apple (with skin) 3
1 medium banana 3
1/2 cup blackberries 3
5 dried dates 3
1 medium nectarine 3
1 medium peach (with skin) 3
1/4 cup roasted peanuts 3
1 cup strawberries 3
1 pear (with skin) 2
1/4 cup cantaloupe 2
10 medium olives 2
1 medium orange 2
2 tablespoons smooth peanut butter 2
1 medium tangerine 2
1/4 cup walnut pieces 2
1 medium apricot 1
10 large cherries 1
1/2 medium grapefruit 1
1/2 cup pineapple 1
2 tablespoons raisins 1
2 medium plums <1
1/2 cup orange juice 0

This material does not cover all information and is not intended as a substitute for professional medical care.


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