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The
glycemic index isn't practical for most people
July 27, 2006
Suzanne Havala Hobbs
Our
national obsession with carbohydrates is waning, but one tool
of carb counters – the glycemic index – continues
to generate interest.
To understand what the glycemic index is, you have to know
what a carbohydrate is. Carbohydrates are nutrients found
in a wide range of foods, including fruits, vegetables, breads,
cereals, beans, milk and sweets.
Your body burns carbs for fuel. In fact, as I mentioned in
this column last week, carbs are your body’s preferred
source of energy. Think of carbohydrates as premium unleaded
fuel in your tank.
Most of your diet should be carbohydrates. Carbs come in the
form of sugars, starches and fiber.
Sugars are the simplest form of carbohydrates and are digested
quickly. Starches are chains of sugars that take longer to
digest, and foods high in fiber take the longest to digest.
When you digest carbs, they break down into glucose, the form
of sugar that enters your bloodstream where your body’s
cells can burn it for fuel.
Different foods make it into your bloodstream at different
rates.
The glycemic index, then, is a system for ranking foods according
to how they affect your blood sugar level. Foods that have
a high glycemic index raise blood sugar levels faster and
higher than foods with a low glycemic index.
Diets rich in foods that have a high glycemic index are linked
with increased risks for diabetes and coronary artery disease.
Popular diet books also claim that high glycemic index foods
cause obesity.
Refined carbohydrates usually have the highest glycemic indices.
White bread, donuts, and cornflakes, for example, have higher
glycemic indices than do whole wheat bread, brown rice and
whole oats.
You can see a comprehensive list of foods and their glycemic
indices online at http://www.glycemicindex.com/.
But the glycemic index isn’t enough to predict a food’s
affect on blood sugar. Some foods, for example, may have a
high glycemic index but have little effect on blood sugar
because they contain so little total carbohydrates. Another
measure – the glycemic load – gives a better view
of how much overall impact a food has on blood sugar.
Even with all of this information, though, you can’t
tell with certainty how your body will respond to a particular
food. Why not?
Because many other factors affect how quickly foods raise
your blood sugar level. Some things that make a difference:
* Ripeness. A ripe banana has more sugar than a green banana,
so its glycemic index is also higher. Glycemic index can also
vary by the variety of a food and location it’s grown
in, as well as how it’s prepared.
* Individual variation. You and I may differ in how our bodies
respond to various foods.
* Degree of refinement. Highly refined grains are more quickly
digested than grains that are less refined. The more intact
fiber a food contains, the lower the glycemic index is likely
to be.
* The context of the meal. If you eat a high glycemic index
food with foods that have low glycemic indices, you’ll
lower your overall glycemic response to the meal.
So here’s the bottom line:
In practice, the glycemic index isn’t a very practical
tool for daily meal planning for most people. Instead, the
take-away message is this: Choose foods as close to their
natural state as possible, opting for whole grain breads and
cereals over refined and getting plenty of fiber-rich beans,
vegetables and fruits in your diet every day.
As complex as the science is, the basic advice is really fairly
simple.
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