A high-fiber diet is a diet in which the individual
consumes foods that meet or exceed the dietary reference
intake (DRI) for dietary fiber set by the United
States Institute of Medicine (IOM) of the National
Academy of Sciences
No single person developed the high-fiber diet.
Over the years, researchers have compared the rate
of various chronic diseases in populations that had
high-fiber diets with those that had lower dietary
fiber intake. They found, for example, that native
Africans who ate a high-fiber, plant-based diet are
rarely bothered by constipation.
However, in industrialized
countries where a lot of animal products are
consumed, constipation is common. Observations like
this encouraged researchers to look at other roles that
dietary fiber might play in health. From their findings
came a consensus that a high-fiber diet is a healthy
diet. This is reflected in the Dietary Guidelines for
Americans 2005, which encourage people to eat more
high-fiber foods such as whole grains.
The United States Institute ofMedicine (IOM) of
the National Academy of Sciences has set dietary
reference intakes (DRIs) for fiber based on research
data that applies to American and Canadian populations.
DRIs provide nutrition guidance to both health
professionals and consumers. The current daily DRIs
for fiber are as follows:
-children ages 1–3 years: 19 grams
-children ages 4–8 years: 25 grams
-men ages 14–50: 38 grams
-men age 51 and older: 30 grams
-girls ages 9–18: 26 grams
-adult women ages 19–50: 25 grams
-women age 51 and older: 21 grams
-pregnant women: 28 grams
-breastfeeding women: 29 grams
The average American consumes only 14 grams of
fiber each day, despite extensive research that shows
that higher levels off fiber provide increased health
benefits. The purpose of a high-fiber diet is to encourage
people to eat more fiber in order to receive the
advantages of those health benefits. The high-fiber
diet is not designed specifically to be a weight loss
diet, although weight loss may occur as a side effect
of the diet.
Dietary fiber is the collective name for a group of
indigestible carbohydrate-based compounds found in
plants. They are the materials that give the plant
rigidity and structure. Two types of fiber are important
to human health, insoluble fiber and soluble fiber.
Insoluble dietary fiber from the plants moves
through the digestive system essentially unchanged.
It is not digested, and it does not provide energy
(calories). Instead, fiber adds bulk to the waste (stool
or feces) in the large intestine (colon). Increased bulk
causes the walls of the intestine to contract rhythmically
(peristalsis), so that waste moves through the
large intestine more rapidly. In the colon, most of the
water in digested food is reabsorbed into the body,
and then the solid waste is eliminated. By passing
through the colon more rapidly, less water is reabsorbed
from the waste. The stool remains soft and
moist and is easy to expel without straining.
Good sources of insoluble fiber include:
-whole grains and foods made of whole grains, such as
whole wheat bread and whole wheat pasta, couscous,
or bulgur
-bran and bran breakfast cereals
-brown rice
-carrots, cucumbers, and other raw vegetables.
Soluble fiber is found dissolved in water inside
plant cells. Like insoluble fiber, it is not digested and
does not provide energy, although it may be consumed
by bacteria that live in the digestive tract. In water,
soluble fiber forms a gel-like substance. This gel
absorbs water and helps to keep the stool soft. Good
sources of insoluble fiber include:
-oatmeal and foods made with oats
-foods such as chili or split pea soup that contain
dried beans and peas
-lentils
-apples
-pears
-citrus fruits
Because fiber is so important in the diet, the
amount of fiber in canned goods, frozen foods, and
other processed foods sold commercially must be
shown on the label. A food that is labeled ‘‘high in
fiber’’ contains 5 or more grams of fiber per serving.
As of mid-2007, manufacturers were required to show
only the total amount fiber in each serving of food.
However, at this time regulations were under consideration
that that would require soluble dietary fiber to
be listed separately from total fiber. This is because
soluble fiber has health benefits that insoluble fiber
does not. A good list of high-fiber foods can be found
at <http://www.gicare.pated/edtgs01.htm>.
