Fiber is a complex carbohydrate that comes from the edible parts of plants, including vegetables, fruits, grains, and legumes. There is no dietary fiber in meat or dairy products. Fiber, which contains no calories, is vital for good health, yet it is not a nutrient. It cannot be digested, absorbed into the bloodstream, or used by the body for energy.
Types of Fiber
There are two types of fiber, soluble and insoluble. Some foods contain both types. Generally, vegetables have more insoluble fiber, and fruits contain more soluble fiber. Consume adequate amounts of fiber from a variety of foods.
Soluble Fiber dissolves in water and develops a soft, mushy texture when cooked. Sources include dry beans and peas, lentils, whole oats, oatmeal, oat bran, ground barley, flaxseeds, many vegetables and fruits, and psyllium seeds.
Insoluble Fiber does not dissolve in water but can absorb water. It has a tough, chewy texture. Sources are whole-wheat products, wheat bran, oat bran, corn bran, flaxseeds, many vegetables, fruits with skins, root vegetables, and legumes.
Health Problems from Eating Too Little Fiber
Over the course of a lifetime, a low fiber diet (less than 20 grams per day) can result in numerous health problems, including:
- Colon Cancer
Benefits of Fiber
A high-fiber diet (25 to 38 grams per day) may lower the risks for:
- Heart Disease
- Type 2 Diabetes
- High Cholesterol
- Certain types of cancer
Fiber helps provide the feeling of fullness on fewer calories; therefore, it is beneficial when trying to lose weight.
Soluble fiber mixes with liquid in the digestive tract, binds to fatty substances, and removes them from the body without allowing them to be absorbed. Consuming adequate amounts of it may help to lower cholesterol, as well as reduce the amount of cholesterol manufactured by the liver. Foods high in soluble fiber help to lower LDL (“bad”) cholesterol without lowering HDL (“good”) cholesterol.
In addition, soluble fiber helps lower or stabilize blood sugar levels by slowing the rate at which carbohydrates break down and glucose is released into the bloodstream; therefore, it plays a role in preventing and treating type 2 diabetes.
Insoluble fiber, also known as roughage, helps the colon function properly. Insoluble fiber acts as “nature’s broom,” absorbing water and moving waste through the intestinal tract. It adds bulk and softness to the stool, which promotes regularity and relieves constipation. It also reduces the formation of hemorrhoids and diverticulosis by putting less pressure on the colon walls. If the walls of the colon get weak, tiny sacs can form and become infected, causing a painful problem called diverticulitis.
In addition to promoting regularity in children, fiber helps them establish eating patterns that may reduce the risk of developing heart disease and some types of cancer later in life.
How Much Is Enough?
Adults: There is no Recommended Dietary Allowance (RDA) for fiber. The Academy of Nutrition and Dietetics recommends 25 to 38 grams of fiber per day for adults. At least 5 to 10 grams of this total should be soluble fiber. Currently, most Americans fall short of this goal, consuming only 15 grams of fiber daily.
A diet too high in fiber is not recommended. Eating more than 50 to 60 grams of fiber daily may lower the body’s absorption of certain vitamins and minerals. Adults over the age of sixty-five, as well as those who have had gastrointestinal surgery, may experience problems with added fiber.
Children: Like adults, most children do not get enough fiber in their diets. The fiber recommendation for children ages three to eighteen is to add five to the child’s age. For example, a five-year-old child needs about 10 grams of fiber, 5 + 5 = 10. As the child grows, this formula allows for increases in the need for fiber.
After children reach the age of two, their dietary fat should be lowered gradually, reaching the level recommended for adults around age five. As dietary fat is reduced, more foods rich in fiber, vitamins, and minerals should be consumed.
Since foods high in fiber tend to be bulky and low in calories, high-fiber diets can fill children up quickly, reducing the total calories and vital nutrients that they consume. In addition, fiber can interfere with vitamin and mineral absorption.
Children’s dietary fiber should be increased gradually by consuming more fruits, vegetables, legumes, cereals, and other grain products. When increasing fiber intake, children should also drink more liquids, including water, juice, and milk.
The average American consumes only 15 grams of fiber daily, choosing grain products, fruits, and vegetables with only 1 to 3 grams of fiber per serving.
Avoid Fiber Pills & Powders: Their primary benefit is to relieve constipation, and the body may come to depend on them. Supplemental fiber may lead to mineral deficiencies, especially during pregnancy, lactation, adolescence, or when mineral intake is too low. Therefore, save the expense of fiber pills and powders.
Drink Plenty of Liquids: When eating a high fiber diet, drink eight or more cups of liquids daily, including water, juice, and milk. Fiber holds water like a sponge while moving waste through the colon and avoiding constipation.
Add Fiber Gradually: A high-fiber eating plan is important to your health, but fiber can have side effects, including intestinal bloating and gas. These often result not only from what is eaten but how quickly it is eaten. Chewing more slowly to break down the fiber compounds makes digestion easier.
When adding higher-fiber foods to the diet, incorporate them gradually, allowing time for the digestive tract to adjust to the increase. It may take several months for the bacteria in the stomach and intestines to adjust. Otherwise, gas, diarrhea, cramps, and bloating will occur.
Ways to Get More Dietary Fiber:
- At mealtime, fill 75% of the plate with fruits, vegetables and grain products.
- Increase daily intake of fruits and vegetables to 2 cups fruit and 2½ cups vegetables. This is based on a 2,000-calorie daily intake, so increase or decrease this amount depending on energy or caloric needs.
- Eat a variety of fruits and vegetables, including all five vegetable subgroups: dark green, orange, legumes, starchy vegetables, and other vegetables.
- Check the Nutrition Facts on food labels, and select high fiber foods, as well as those with fiber-rich ingredients.
- Eat legumes two to three times per week. Legumes include beans, peas, and lentils, which are excellent, inexpensive sources of fiber and protein. One-half cup of cooked dry beans, peas, or lentils counts as 1 ounce of meat in the diet.
- Try main dishes made with beans rather than meat, such as bean burritos and vegetarian chili with beans. If bean dishes cause intestinal gas, try eating smaller servings.
- Eat 6 or more ounce-equivalents* of grains per day, with at least half of this amount being whole grain products. Examples are 100% whole wheat, whole oats, brown rice, rye, barley, and quinoa. The word “whole” should appear in front of the grain on the ingredient list of crackers, breads, and cereals.
- *A 1 ounce-equivalent is 1 slice of bread, 1 cup dry cereal, or ½ cup cooked rice, pasta, or cereal. Snack on high-fiber foods like fresh fruit, raw vegetables, popcorn, and nuts. Add sliced fresh fruit to yogurt or cottage cheese. Use fresh fruit slices instead of jelly on peanut butter sandwiches.
- Replace white rice with brown rice.
- Choose breakfast cereals with five or more grams of fiber per serving, and top with fruit for more fiber. An excellent choice is whole grain cereal with strawberries, blueberries, or raspberries. Avoid refined, sugary cereals.
- Enjoy the edible skin and seeds of fruits and vegetables. For example, eat the skin of a baked potato for more fiber.
- It is best to select whole fruits and vegetables over fruit and vegetable juice because the peel and pulp contain fiber.
- Steam or stir fry vegetables just until they are tender but still crisp.
- Add high fiber ingredients in recipes:
- Use oatmeal in meatloaf
- Add extra vegetables to salads, soups, casseroles, and pasta dishes
- When baking, substitute up to one-third of the flour with quick or old-fashioned oats
- Replace all or part of the white flour with whole wheat flour
- Add ground flaxseeds, wheat germ, sunflower seeds, or sesame seeds to baked goods
- Top casseroles with wheat germ, sesame seeds, or sunflower seeds
Per serving: Calories 119, Total fat 1g, Cholesterol 0mg, Sodium 196mg, Total Carbohydrate 27g, Dietary fiber 4g, Protein 4g, Potassium 524 mg.
Originally published 09/05