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In recent years, researchers have looked more
and more at how the type and amount of carbohydrates that we
eat can affect our health. A recent study helps build the case
that the kind of carbohydrates and the quantity in our diet
can influence our risk for cancers of the colon, uterus and
stomach. But care is needed in evaluating what the research
in this area that centers around concepts called glycemic index
and glycemic load really says.
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May 21, 2004
Glycemic index refers to how a particular food affects the
body's sugar and insulin levels. Common sense says that sugars
in foods always raise blood sugar more than starches, but glycemic
index testing shows that potatoes can raise blood sugar and
insulin levels at least as much as pure sugar. Trying to eat
foods with low glycemic index readings, however, is tricky.
A food's effect on one's blood sugar depends on what else is
eaten, the portion size, and how it's prepared.
Glycemic load
may be more significant
The term glycemic load, on the other
hand, tries to calculate the combined value of one or more
foods' glycemic index readings and how much of them a person
eats. It can be used to describe the effects of one food, a
meal, a whole day's eating, or eating over many days. In many
recent studies, the glycemic load of a person's overall diet
is more significant than the glycemic index of individual foods.
For example, one recent report from the large national Women's
Health Study shows that women with the highest glycemic load
are nearly three times as likely to develop colorectal cancer
in the next eight years than those with the lowest glycemic
load. In an earlier study, men and women with the highest glycemic
load were 80 percent more likely to develop colon cancer compared
to those with the lowest load.
A high glycemic load may also
raise the risk of uterine and stomach cancer by 24 to more
than 100 percent, compared to those with lower glycemic loads.
Researchers think that diets that repeatedly raise blood sugar
levels cause insulin levels to soar. Insulin and insulin-related
growth factors, in turn, appear to promote the development
of some cancers.
Focus on healthier carbs
The positive link
between low-glycemic-load eating habits and better health helps
explain why populations around the world who eat plant-based
diets that emphasize vegetables, fruits, whole grains and beans
have fewer cancers and heart disease than we have in the U.S.
In contrast to the low-carbohydrate diets popular here, these
foreign populations eat high-carbohydrate diets. Their carbohydrates,
however, are not our 24-ounce soft drinks and super-size baked
goods made with refined flour.
It is important to note in the
connection between glycemic load and disease that a low-glycemic
diet will not in itself protect against disease. It makes a
difference whether such a diet comes from ample portions of
vegetables, fruits and unrefined whole grains or massive amounts
of meat. Either one can have a low glycemic load value.
Some
people embrace a low-glycemic diet in an attempt to lose weight.
But selecting foods with a low glycemic load will not bring
automatic weight loss. Whether you gain or lose weight depends
on the balance between the calories you consume and the calories
you burn up. It doesn't matter if you are strict and eat only
meals and snacks with a low-glycemic load. If you overeat,
you'll still gain weight if you don't exercise more.
In summary,
the glycemic theory offers a way for people to examine and
think about their eating habits. But it does not lay out a
plan for good nutrition. To improve what you eat and decide
the appropriate amounts of food, you should turn to a nutrition
authority like the American Institute for Cancer Research.
Nutrition Notes is provided by the American
Institute for Cancer Research in Washington, D.C.
© 2004 MSNBC Interactive
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