How much fiber do I need?

According to the U.S. Department of Agriculture, the average American woman gets about 12 grams of fiber a day from food; the average American man, 17 grams. Those figures are well below the new IOM (Institute of Medicine) recommendations that I conveniently list here:

  • 25 grams a day for women younger than 50
  • 38 grams a day for men younger than 50
  • 21 grams a day for women older than 50
  • 30 grams a day for men older than 50

The amounts of dietary fiber recommended by IOM are believed to give you the benefits you want without causing fiber-related — um — unpleasantries. Unpleasantries? Like what? And how will you know if you’ve got them?

Trust me: If you eat more than enough fiber, your body will tell you right away. All that roughage may irritate your intestinal tract, which will issue an unmistakable protest in the form of intestinal gas or diarrhea.

In extreme cases, if you don’t drink enough liquids to moisten and soften the fiber you eat so that it easily slides through your digestive tract, the dietary fiber may form a mass that can end up as an intestinal obstruction

If you decide to up the amount of fiber in your diet, follow this advice:

  • Do so very gradually, a little bit more every day. That way you’re less likely to experience intestinal distress. In other words, if your current diet is heavy on no-fiber foods such as meat, fish, poultry, eggs, milk, and cheese, and low-fiber foods such as white bread and white rice, don’t load up on bran cereal (35 grams dietary fiber per 3.5-ounce serving) or dried figs (9.3 grams per serving) all at once.

Start by adding a serving of cornflakes (2.0 grams dietary fiber) at breakfast, maybe an apple (2.8 grams) at lunch, a pear (2.6 grams) at mid-afternoon, and a half cup of baked beans (7.7 grams) at dinner. Four simple additions, and already you’re up to 15 grams dietary fiber.

  • Always check the nutrition label whenever you shop (for more about the wonderfully informative guides). When choosing between similar products, just take the one with the higher fiber content per serving.

For example, white pita bread generally has about 1.6 grams dietary fiber per serving. Whole wheat pita bread has 7.4 grams. From a fiber standpoint, you know which works better for your body. Go for it!

  • Get enough liquids. Dietary fiber is like a sponge. It sops up liquid, so increasing your fiber intake may deprive your cells of the water they need to perform their daily work. That’s why the American Academy of Family Physicians (among others) suggests checking to make sure you get plenty fluids when you consume more fiber.

Table 8-2 shows the amounts of all types of dietary fiber — insoluble plus soluble — in a 100-gram (3.5-ounce) serving of specific foods. By the way, nutritionists like to measure things in terms of 100-gram portions because that makes comparing foods at a glance possible.

Food Grams of Fiber in a 100-Gram (3.5-Ounce) Serving
Bagel 2.1
Bran bread 8.5
Pita bread (white) 1.6
Pita bread (whole wheat) 7.4
White bread 1.9
Bran cereal 35.3
Bran flakes 18.8
Cornflakes 2.0
Oatmeal 10.6
Wheat flakes 9.0
Barley, pearled (minus its outer covering), raw 15.6
Cornmeal, whole grain 11.0
De-germed 5.2
Oat bran, raw 6.6
Rice, raw (brown) 3.5
Rice, raw (white) 1.0–2.8
Rice, raw (wild) 5.2
Wheat bran 15.0
Apple, with skin 2.8
Apricots, dried 7.8
Figs, dried 9.3
Kiwi fruit 3.4
Pear, raw 2.6
Prunes, dried 7.2
Prunes, stewed 6.6
Raisins 5.3
Baked beans (vegetarian) 7.7
Chickpeas (canned) 5.4
Lima beans, cooked 7.2
Broccoli, raw 2.8
Brussels sprouts, cooked 2.6
Cabbage, white, raw 2.4
Cauliflower, raw 2.4
Corn, sweet, cooked 3.7
Peas with edible pods, raw 2.6
Potatoes, white, baked, w/skin 5.5
Sweet potato, cooked 3.0
Tomatoes, raw 1.3
Almonds, oil-roasted 11.2
Coconut, raw 9.0
Hazelnuts, oil-roasted 6.4
Peanuts, dry-roasted 8.0
Pistachios 10.8
Corn chips, toasted 4.4
Tahini (sesame seed paste) 9.3
Tofu 1.2

Provisional Table on the Dietary Fiber Content of Selected Foods (Washington, D.C.: U.S. Department of Agriculture, 1988)

To find the amount of dietary fiber in your own serving, divide the gram total for the food shown in Table 8-2 by 3.5 to get the grams per ounce, and then multiply the result by the number of ounces in your portion.

For example, if you’re having 1 ounce of cereal, the customary serving of ready-to-eat breakfast cereals, divide the gram total of dietary fiber by 3.5; then multiply by one.

If your slice of bread weighs 1⁄2 ounce, divide the gram total by 3.5; then multiply the result by 0.5 (1⁄2). Or — let’s get real! — you can look at the nutrition label on the side of the package that gives the nutrients per portion.

Finally, the amounts on this chart are averages. Different brands of processed products (breads, some cereals, cooked fruits, and vegetables) may have more (or less) fiber per serving.