"Fiber" is any food matter that your digestive system can't break into units small enough to be absorbed into the bloodstream. Some fiber is tough, stringy material that won't dissolve in water; the rest is pectins, gums, and mucilages, which do dissolve. Together, the two varieties are termed "dietary fiber."
Dietary fiber should not be confused with crude fiber, a term for what remains after a food is subjected to certain laboratory solvents. A food may contain a lot more dietary fiber than its crude-fiber reading indicates.
A third term, functional fiber, includes both dietary fiber and other fibers (some of them artificial) that a) are deliberately added to foods by manufacturers and b) provide health benefits similar to those of dietary fiber. (Despite label claims, not all added fibers have proven health benefits.) Together, dietary and functional fiber are called total fiber¾a term generally meaning "fiber that has health benefits."
Although dietary and functional fiber are not digested by the body itself, part of them is broken down by friendly bacteria living in the intestinal tract, and the byproducts eventually enter the bloodstream.
Dietary and functional fiber are thought to be valuable for at least three reasons:
They help to lower blood cholesterol, thereby protecting
against heart disease and stroke.
They absorb water and add bulk to the stools,
stimulating prompt elimination of harmful wastes that may be a culprit
in colon cancer. (According to the September 2002 Food
and Nutrition Board (FNB) report on macronutrients, however, evidence for this is "inconclusive.")
They may promote weight control¾but again, the FNB's September 2002 report says evidence on this point is inconclusive.
Good sources of dietary fiber include broccoli, bran cereals, baked beans, peas, whole-wheat breads and cereals, potatoes, carrots, and pears.
It is possible, though difficult, to get too much dietary and functional fiber. The most obvious effect is increased intestinal gas. This diminishes over time, however, and may not happen if you increase your intake gradually.
A high-fiber diet can also lead the body to absorb less of other nutrients, because food remains in the digestive tract a shorter time. Hence, if your intake of another nutrient is borderline, you should increase that before augmenting your fiber intake.
Your Daily Allowance
Diet Power sets your Personal Daily Allowance (PDA) of total fiber at the official Recommended Dietary Allowance (RDA), which varies with age, sex, and reproductive state. For men, the RDA is 38 grams from age 14* through 50 and 30 grams thereafter. For women, it is 26 grams from age 14* to 18, 25 grams from age 19 through 50, and 21 grams thereafter. For pregnant women, it is 28 grams from age 14 through 50. During lactation, the RDA is 29 grams for age 14 through 50. (In the rare event that you are over 50 and pregnant or lactating, Diet Power will assign you the 50-and-younger PDAs for those states. You should review these with your doctor, however.)*
Many experts believe, however, that eating up to twice the RDA would be more healthful.
Before September 2002, there were no RDAs for fiber. Hence, older versions of Diet Power set your PDA of dietary fiber at the Daily Value of 25 grams. If you've upgraded from an older version, your old records will still reflect the absolute amount of dietary fiber that you logged. But the "% PDA" in your Nutrient History will differ, because it's based on the new RDA.
The FNB has not established a Tolerable Upper Intake Level (UL) for dietary fiber.
Revising Your Allowance
If your doctor advises a different allowance, you can revise your PDA -- see Personal Daily Allowances, Editing Your.
Color Coding of This Nutrient
NOTE: Food manufacturers and restaurants do not yet distinguish between dietary fiber and functional fiber, nor does the USDA database from which our Food Dictionary derives. Hence, your personal Nutrient History and each food's nutrient profile do not reflect total fiber¾they reflect only dietary fiber. This will make no practical difference, however, unless you're eating large amounts of foods containing artificially added fiber.
The dietary-fber bar in your personal Nutrient History is:
blue for "good"
if you've logged 100 to 300 percent of your PDA
red for "bad" if you've logged less than 100
percent of your PDA
yellow for "caution"
if you've logged more than 300 percent of your PDA
missing if you've logged no dietary fiber.
In the Nutrient Profile of a food or recipe, the dietary-fiber bar is:
green for "good" if
getting your entire PDA of calories from this item would give you more
than 150 percent of your PDA of dietary fiber
magenta for "bad"
if getting all your calories from the item would give you less than 50
percent of your PDA of dietary fiber
for "neutral" otherwise
missing if the amount of dietary fiber is either zero or (when the term Dietary Fiber is grayed out) unknown.
How Complete Are Diet Power's Fiber Readings?
For the 8500 generic items in the Food Dictionary: fairly complete. Only 17 percent list their dietary-fiber content as "unknown."
For the 2500 chain-restaurant items: fairly complete. Only 17 percent list dietary fiber as "unknown."
For all 11,000 items combined: fairly complete. Only 17 percent list dietary fiber as "unknown."
These figures mean that if you frequently eat fiber-rich foods, your Nutrient History may underreport your intake of dietary fiber by a few points.
To see whether a particular food has a dietary-fiber reading, open the Food Dictionary and check the food's nutrient profile. If you find a question mark beside "Dietary fiber," it means the amount is unknown. (To see all foods with unknown dietary-fiber readings, click the dictionary's PowerFoods tab and sort the foods by dietary-fiber power; then scroll toward the bottom of the list until you see foods with question marks in the "Power Rating" column.)
Dietary Fiber on Food Labels
Nearly all food labels are required to report dietary-fiber content, in both grams and percent of Daily Value. (Labels do not yet distinguish between dietary fiber and functional fiber, however. For definitions of these terms, see the opening paragraphs above.)
The Daily Value for dietary fiber is 25 grams. As noted above, however, a considerably higher amount is believed more beneficial.
For more on label regulations, see Labels, Food.
Got a Suggestion for This Page?
Last Modified: 1/1/07