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Dietary
Fiber
Dietary
fiber is a type of carbohydrate found only in plant foods. It's basically
derived from the material that helps give plants their shape and structure.
Fiber falls into two distinct categories—insoluble fiber
and soluble fiber. Most plant foods contain a combination of
both soluble and insoluble fiber in varying amounts.
Insoluble fiber, which is found in high amounts in whole grains as
well as beans, fruits and vegetables, is coarse in texture. Soluble
fiber, on the other hand, has a soft and gummy texture and is found
in high amounts in legumes (beans, peas and lentils), fruits, vegetables,
oats and barley.
Soluble and insoluble fiber actually work in different ways to promote
health.
Insoluble
fiber
Insoluble fiber acts like a sponge and absorbs water as it's digested,
so it adds bulk and softness to bowel movements. This not only prevents
constipation, but also speeds the rate at which food passes through
your system—leaving less time for certain foods to deposit
impurities and cancer promoting compounds on the intestinal wall.
This may be one reason why diets high in fiber are associated with
low rates of bowel and colon cancer. Recent results from one of
the largest studies ever conducted into the link between diet and
cancer—the EPIC (European Prospective Investigation of Cancer
and Nutrition) Study—involving more than 500,000 people from
10 countries for nearly five years, found that the people eating
the most fiber had a 40 percent lower risk of colon cancer than
those people eating the least.
Soluble
fiber
Soluble
fiber works differently from insoluble fiber because it's broken
down by the action of bacteria in the digestive tract and some of
the healthy by-products of this process are absorbed into the blood
stream. Once in the blood stream these healthy by-products have
been found to bind with bile acids (compounds originally derived
from cholesterol stores in the liver) and escort them out of the
body. This draws cholesterol from the blood, and in turn lowers
cholesterol levels. In one study of men with high cholesterol levels,
adding half a cup of cooked dried beans (rich in soluble fiber)
to their normal diet reduced their blood cholesterol
levels by 13 percent in 21 days. Soluble fiber also slows the release
of glucose into the bloodstream, which helps regulate blood sugar
levels.
Both
soluble and insoluble fiber have also been shown to protect against
heart disease and breast cancer. In a study of over 43,000 U.S.
male health professionals conducted by Harvard University, it was
found that over a six-year period those who ate the most fiber had
a 55 percent lower chance of coronary death than those who ate the
least. And a recent study of more than 1000 Australian women (half
had been diagnosed with breast cancer, half were free of the disease)
found that those who ate more than 28 grams of fiber per day had
the lowest risk of the disease, while those who ate less than 14
grams per day faced the highest risk.
The
weight loss bonus
Fiber not only promotes good health and keeps you regular, it can
also help control your weight. Here's why. Firstly, fiber is nature's
best appetite suppressant because it fills the stomach and satisfies
your appetite much earlier than fiber depleted foods. And fiber
isn't only bulky and filling, it also can't be digested like normal
foods (it basically passes right through you) so it adds virtually
no calories to your diet.
The
chewiness of high-fiber foods also prolongs eating time which, in
turn, gives your body time to tell your brain that your stomach
is full.
And a high-fiber diet may actually cut the number of calories you
ingest by blocking your body's ability to digest the fat and protein
consumed along with it. In a recent study by the U.S. Department
of Agriculture, researchers set a certain number of calories for
subject groups and altered the fiber content. Results demonstrated
that fewer calories were absorbed with increased fiber intake. It
was found that people who consumed up to 36 grams of fiber a day
absorbed 130 fewer daily calories. Over a year, that adds up to
over 47,000 calories!
Are
you getting enough?
The
importance of fiber as part of a healthy diet is beyond question.
Unfortunately most people in Western countries like the U.S., the
U.K. and Australia consume very little dietary fiber—only around
10-15 grams a day. While this is better than none, it's too little
for any appreciable benefits. Throughout the Mediterranean and Asia
fiber intake is traditionally between 30-40 grams a day. This is
the level to strive for. Luckily by following a MediterrAsian style
of eating—which includes lots of fiber-rich whole grains, fruits,
vegetables, nuts and legumes—you'll naturally be eating this
level of fiber without even having to think about it.
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