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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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