Linda Boeckner, Extension
Nutrition Specialist
Defining Fiber and Its Role
Food fibers are that part of plant foods
that are not digested when eaten. Since they are not absorbed into the body, dietary
fibers are not a nutrient. Nevertheless, consumers are increasingly interested
in the role that dietary fibers play in maintaining the body's health.
Fiber-rich foods help with constipation,
hemorrhoids, and diverticular disease. Some types of fiber may have a
cholesterol-lowering effect which could lead to reduced risk of heart disease.
In addition, fiber may reduce the incidence of certain types of cancer,
particularly those associated with the digestive tract, and may be helpful in
controlling diabetes.
Soluble and insoluble fibers make up the two
basic categories of dietary fiber. Insoluble fibers — cellulose, hemicellulose
and lignin — are not soluble in water. Foods which contain insoluble fibers are
wheat bran, whole grain products, and vegetables. Insoluble fibers are
responsible for increased stool bulk and help to regulate bowel movements.
Soluble fibers — gums, pectins, and
mucilages — become gummy in water. When eaten, these fiber sources actually
slow the passage of food through the digestive system. Some researchers believe
this action helps to regulate cholesterol and glucose (sugar) levels in the
blood by affecting absorption rates. Food sources of soluble fibers are dried
beans, oats, barley and some fruits and vegetables.
Placing too much emphasis on
one type of fiber or fiber-rich food is risky. Achieving balance in eating
dietary sources of fiber is a key concept. Excessive intakes of insoluble
fibers such as wheat bran to the exclusion of soluble fibers will result in a
bulky diet but the benefits of the soluble fiber will be lost. Furthermore,
excessive fiber intake without adequate fluid intake can result in abdominal
pain and discomfort.
Nutrition researchers and
educators recommend that healthy adults consume between 20-35 grams of dietary
fiber per day1. According to current studies, American men and women eat about
11 grams of dietary fiber daily2. If you plan to add more fiber to your diet,
follow these steps:
The Dietary Guidelines for Americans
recommend that we get our fiber in the following ways3: Three or more servings
of various vegetables. Count one cup of raw leafy greens or 1/2 cup of other
vegetables as a serving. Have dark-green leafy and deep-yellow vegetables
often. Eat dry beans and peas often. One-half cup cooked dry beans or peas is a
serving of vegetables. It may also count as one ounce of a meat serving.
Two or more servings of various fruits.
Examples of servings are one medium apple, orange or banana; 1/2 cup of canned
fruit; or 3/4 cup of juice. Eat citrus fruits or juices, melons or berries
regularly to get vitamin C. Select fruits as desserts.
Six or more servings of grain products such
as breads, cereals, pasta, and rice. A serving is 1 slice of bread; 1/2 bun,
bagel or English muffin; 1 ounce of dry cereal; and 1/2 cup of cooked cereal,
rice or pasta. To boost fiber, have several servings of whole-grain breads and
cereals daily. Eat products from a variety of grains.
Drink plenty of fluids. Six to eight glasses
a day will help reduce the risk of abdominal discomfort and intestinal blockage
caused by too much fiber.
Get fiber from foods not pills. Food sources
are more efficient and will supply additional nutrients. Excessive use of fiber
supplements can lead to acute digestive problems and blockages. The American
Dietetic Association advises that intakes greater than 50-60 grams a day can
also block the absorption of some nutrients4.
Dietary Fiber in Foods*
|
|
Serving size |
Total Fiber (grams) |
Soluble Fiber (grams) |
Insoluble Fiber (grams) |
|
BREAKFAST CEREALS |
||||
|
All-Bran |
1/3 c (28 gm) |
8.43 |
.59 |
7.84 |
|
Cornflakes |
1 1/4 c (28 gm) |
1.20 |
.14 |
1.06 |
|
40% Bran-type |
3/4 c (28 gm) |
5.46 |
.56 |
4.90 |
|
Oatmeal, regular, cooked |
1 c (234 gm) |
4.45 |
1.64 |
2.81 |
|
Puffed rice |
1 c (28 gm) |
.53 |
.14 |
.39 |
|
Shredded Wheat |
2/3 c (28 gm) |
3.16 |
.31 |
2.86 |
|
Wheat germ |
1/4 c (56 gm) |
7.84 |
.62 |
7.22 |
|
|
||||
|
FRUITS |
||||
|
Apple, no skin |
1 med (138 gm) |
2.07 |
.28 |
1.79 |
|
Apple, with skin |
1 med (138 gm) |
2.76 |
.28 |
2.48 |
|
Banana |
1 med (114 gm) |
1.94 |
.57 |
1.37 |
|
Cantaloupe |
1/4 (133 gm) |
.93 |
.13 |
.80 |
|
Grapes |
20 (100 gm) |
1.00 |
.10 |
.90 |
|
Orange |
1 med (131 gm) |
2.49 |
.79 |
1.70 |
|
Pineapple, canned |
1/2 c (125 gm) |
.88 |
.13 |
.75 |
|
Raisins |
1/4 c (36 gm) |
1.51 |
.22 |
1.30 |
|
Strawberries |
1 c (149 gm) |
2.68 |
.60 |
2.09 |
|
|
||||
|
VEGETABLES |
||||
|
Beans, green |
1/2 c (67 gm) |
1.27 |
.34 |
.94 |
|
Broccoli, raw |
1/2 c (78 gm) |
2.57 |
.23 |
2.34 |
|
Cabbage, raw |
1 c (70 gm) |
1.19 |
.07 |
1.12 |
|
Carrots, raw |
1 med (72 gm) |
1.80 |
.14 |
1.66 |
|
Corn, frozen, cooked |
1/2 c (83 gm) |
1.74 |
.08 |
1.66 |
|
Potato, no skin |
1 med (156 gm) |
2.03 |
.47 |
1.56 |
|
Potato, with skin |
1 med (202 gm) |
5.05 |
1.21 |
3.84 |
|
Turnip greens, frozen |
1/2 c (82 gm) |
2.05 |
.08 |
1.97 |
|
|
||||
|
LEGUMES |
||||
|
Kidney beans, canned |
1/2 c (128 gm) |
6.66 |
1.41 |
5.25 |
|
Pork and beans, canned |
1/2 c (128 gm) |
5.63 |
1.79 |
3.84 |
|
Peas, green, frozen |
1/2 c (80 gm) |
2.80 |
.24 |
2.56 |
|
|
||||
|
BREADS, PASTA |
||||
|
Bread, white |
1 sl (25 gm) |
.65 |
.15 |
.50 |
|
Bread, whole wheat** |
1 sl (28 gm) |
2.59 |
.57 |
2.02 |
|
Rice, regular, cooked |
1/2 c (102 gm) |
.41 |
.10 |
.31 |
|
Spaghetti, cooked |
1 c (140 gm) |
2.10 |
.56 |
1.54 |