is comprised of components of plant materials (long
chain glucose molecules) that are resistant to human
digestive enzymes. Fiber plays an important role in
digestion, providing bulk, decreasing bowel transit
time, absorbing toxins and cleaning the colon of mucus
and undigested food particles. Fiber acts to increase
the thickness of the stomach contents which gives a
feeling of fullness and slows down the emptying of the
stomach. Later in the process, as fiber moves through
the system its bulk enables food to pass more quickly
through the bowels while it absorbs toxins, excess bacteria
and mucus in the intestines and contributes to easier
and more normal bowel movements.
Fiber comes in two
forms — soluble and insoluble. Soluble fiber absorbs
up to 15 times its weight in water as it moves through
your digestive tract, producing softer stools. It's
most abundant in oats, legumes and fruits. Insoluble
fiber, found in vegetables and whole grains, gives stool
its bulk. Softening and bulking of stool helps to prevent
constipation, some types of diarrhea and symptoms of
irritable bowel syndrome. These actions also decrease
pressure in the intestinal tract, reducing the risk
of hemorrhoids and diverticular disease (a condition
in which pouches form in the intestinal walls). Unfortunately
many people don’t get enough fiber. Americans
typically consume 10 to 15 grams of fiber with most
dietary guidelines recommending twice that amount. This
correlates with bowel transit times of up to 96 hours,
more than twice what it should be (12 to 24 hours).
The solution is increasing fiber intake to recommended
levels through diet or fiber
supplements or a combination of the two.
and Colon Cancer
In addition to its obvious benefits in speeding and
improving digestion and elimination there is a growing
body of research indicating that fiber has an important
role in the prevention of cancer. Results from the largest
scientific study investigating the relationships between
diet and cancer risk strongly support the role for dietary
fiber in the prevention of colon cancer, according to
the American Institute for Cancer Research (AICR) and
the World Cancer Research Fund International. Results
from the European Prospective Investigation into Cancer
(EPIC) study were published in the British journal The
Lancet. Researchers tracked the diets of 519,978 subjects
in ten European countries for an average of 4.5 years.
They found that those subjects who ate the most dietary
fiber (averaging 35 g/day) had their risk of colon cancer
reduced by 40 percent, compared with subjects who ate
the least fiber (averaging 15 g/day. An American study
published in the same issue of The Lancet used a different
method but reached a similar conclusion. In this case-control
study, researchers with the Prostate, Lung, Colorectal
and Ovarian Cancer Screening project team (PLCO) compared
the fiber intakes of 33,917 subjects without colon adenomas
(non-malignant polyps) to 3,591 subjects with at least
one polyp. Those subjects who ate the most dietary fiber
(more than 30 g/day) had their risk of polyps reduced
by 20 percent, compared to those who ate the least (less
than 15 g/day).
One factor that makes the EPIC study
so unique in the field of diet-cancer research is the
number of subjects it is currently tracking - over half
a million individuals, aged 24-75. Another important
strength of the project is its ability to compare the
widely different diets of 10 European countries - Denmark,
France, Germany, Greece, Italy, the Netherlands, Norway,
Spain, Sweden and the UK. The enormous dietary variation
among these countries means that diet-cancer associations
are easier to identify. In an editorial discussing the
EPIC and PLCO studies, the Lancet concludes, "…eating
a diet rich in plant foods, in the form of fruit, vegetables
and whole-grain cereals probably remains the best option
for reducing the risk of colon cancer, and for more
general health protection."
Some suggestions to increase dietary fiber include:
- Increase grain intake to 6 to 11 servings a day.
These include cereals, breads, rice and pasta. High-fiber
cereals are one of the easiest to find sources as
one serving size can be as high as 8-10 grams of fiber.
Whole-grain breads, brown rice and wheat bran effectively
- Vegetables (3 or more servings a day) are an excellent
source of fiber, especially broccoli, cabbage, cauliflower,
corn, green beans, tomatoes and zucchini.
- Fruits (at least 2 servings per day) including apples,
bananas, apricots, grapes, peaches, and strawberries
and replace processed fruit juice with whole fruit.
- Limit dairy products to 2 to 3 servings or less.
- Limit poultry, seafood and meat to no more than
- Legumes can be used as a high protein, low fat alternative
to animal foods. These include beans, dried peas and
- Use fats, sweets and alcohol sparingly.
- Many nuts are high in insoluble fiber.
your daily intake of fiber should be between 30-40 grams.
Since it’s not always possible to get this amount
through diet alone fiber
supplements and meal
replacers with fiber can be added to the diet.
When choosing fiber supplements its important to limit
soluble fiber supplements (bulking, psyllium based laxatives)
since they extract water from the intestines and cause
dehydration and constipation.