When I was growing up, my mother insisted I get plenty of roughage in my diet. That's what fiber was called in the past. And that's basically what it is. Roughage, the parts of plant food that we as humans don't have the enzymes to digest and absorb.
Why do we need it? My mother told me it was to bulk up the stools--and again she was right--for one of the reasons. Fiber holds onto water and fluids and softens the stools so they pass with less effort, which decreases constipation--which then decreases straining and all the diseases that are associated with that-hemorrhoids, diverticulitis, and somehow even heart disease--or that may be because the fiber can also bind to cholesterol and fats. Because fiber holds extra water, it can even help in some cases of long standing (chronic) diarrhea.
Because fiber is filling, it can also lessen total calorie intake, and potentially help with weight control. Fill up on carrots and celery, you may have as much room for that slice of chocolate cake you otherwise wouldn't have the will power to avoid. And certain fiber products, particularly the soluble fibers of oats are known for lessening cholesterol.
Types of Fiber
That last paragraph said a lot. First that there are different types of fiber, based on whether they dissolve in water. Soluble fiber, the kind found in oats, fruits, beans and psylllum (which is used in lots of fiber pills and products), forms a gel (jello-like) with fluid. That gel slows stomach emptying, and in doing so, helps to regulate sugar and insulin levels as well as lower blood cholesterol levels. Insoluble fiber, in vegetables and other whole grains, pretty much remain the same passing through the intestine, providing much of the intestinal bulk.
The second point is that fruits and vegetables are excellent sources of fiber (see the table) but they are often ignored with all the focus on whole grains in various cereals, breads and pastas.
Each serving has approximately 2 grams of fiber. Older infants should have one or two each day. Avoid giving fruit with pits to infants. Remember to remove skins and seeds.
Apple, 1 small Cantaloupe, 1 cupa Pear, 1/2 small
Apricot, 2 medium Cherries, 10 large, pitted Plum, 2 small
Banana, 1 small Dried figs, 1.3 cup Strawberries, 1/2 cup
Blackberries, 1/2 cup Peach, 1 medium Watermelon, 1–3 cupsa
Each serving has about 2 grams of fiber. Children should have two servings or more each day. Children 6 to 12 months should have one to two fistfuls per day; children one to three years, half a cup of vegetable per day.
Avocado, fresh, 1/2 medium Carrots, 1/3 cup Potato, 2-inch diameter
Broccoli top, 1/3 cup Green beans, 1/2 cup french fries, 20
Beans, 2 tbsp. Peas, 1/4 cup Sweet potato, 1/2 medium
Bread and Cereal
Infants need iron from infant cereal or meat, approximately 2 ounces per day. Each serving has about 2 grams of fiber (but not needed for infants.
Cherrios, 2/3 cup Animal crackers, 3 boxes (2 oz. each)
White bread, 3 slices Whole-wheat bread, 1 slice Graham crackers, 10 squares Infant rice cereal and puffs have minimal fiber Infant oatmeal, 12 tbsp.
a Estimates vary widely.
Source: Adapted from S. A. Cohen, Healthy Babies, Happy Kids (New York: Delilah Books, 1982), 168.
How Much is Enough? How Much is too much?
Infants should be gradually introduced to fiber, usually as fruits and veggies, so that by a year of age they are consuming 5 grams daily. After that, you can estimate how much a child needs by adding 5 grams to their age. Thus a 3 year old should receive about 8 grams and a 12 year old about 17 grams with adults needing 20-30 grams per day.
I do suggest that fruits and veggies make up a significant portion of that by including 5 or more servings per day. The best way to gauge the amount for each child is by asking them to eat a fistful of each. It's also to remember as "5 fistfuls a day." And sometimes I have them hold their fists together (figure) so I can show them, that's the size of an apple or peach--so that they can see they can easily accomplish the goal.
How Much is Too Much?
The one problem with fiber is that the intestine can digest some of the beans and vegetables and grains, producing gas. Beans, broccoli, cauliflower, cabbage and mushrooms are notorious as gas producers. And that gas can cause cramping and discomfort for some who are particularly sensitive. And for almost everyone, the gas will eventually come out, potentially causing embarrassing moments. A probiotic can sometimes help by providing healthy intestinal bacteria that actually feed off the fiber. But if it doesn't sometimes you can moderate the amount of fiber to lessen the gas while still having enough to benefit your gastrointestinal system.