The Glycemic Index - Which Carb is right for you?
Carbohydrates are made
up of small sugar molecules, which once absorbed into the bloodstream, raises
blood sugar levels, so that the body can have a source of fuel for energy.
People who have the right amount of insulin in their bodies will clear the blood
sugar produced after eating carbohydrate. The glucose (blood sugar) enters the
cells with the help of insulin so that the body can use the glucose for fuel and
will be "burned" so that for most people, blood sugar levels return to
normal fairly quickly after a meal. For people who have Type II diabetes, or
have "insulin resistance" due to obesity or other factors, the body
must work harder to produce more insulin to cover the blood sugar that is
produced following a meal. This is one reason that many popular diets emphasize
reducing the amount of carbohydrate in the diet, and promote the use of the
glycemic index to help choose good and bad carbohydrates. But do you
really need to reduce carbohydrates to very low levels to lose weight and
improve insulin resistance?
The simple answer is no.
A healthy diet is based upon eating a variety of healthy foods, and in fact most
cultures have diets based upon carbohydrate sources. Examples of this are rice
in India and Asia, tortillas and beans in Central America, bread and potatoes in
the U.S. and Europe, and root vegetables in Africa. China, with one of the
lowest incidences of obesity, has a diet based upon rice, a carbohydrate.
The recommended diet for
people with diabetes
(a disease in which the body cannot produce insulin or
cannot use the insulin it produces normally to lower blood glucose) includes
about 50% carbohydrate. Your recommending eating plan at PersonalDiets, for weight loss,
weight maintenance, is at least 50% carbohydrate.
Do not be concerned that
you might be eating too much carbohydrate on your
diet plan. The reality of a
weight loss diet is that, for the most part, it is lower in everything, compared
to a diet that maintains your body weight! Although you may be following a diet
that is 50% carbohydrate (sounds like a lot), 50% of the calories on a 1400
Calorie diet (or your particular calorie level) is probably a smaller amount of
carbohydrate than the total amount of carbohydrate you were eating when you were
gaining or maintaining your body weight at a higher calorie level.
For more basic
information about carbohydrates, please read the archived newsletter in your
member's area "Carbohydrates - Not So Simple."
The Glycemic Index
The glycemic index has
shed new light on how carbohydrates are absorbed, and how they affect blood
sugar. It turns out that some foods made from simple sugars actually raise blood
sugar more slowly than some “complex” carbohydrates.The glycemic index is
one way to categorize foods by how rapidly they increase blood glucose levels,
causing insulin to be released by the pancreas. This can be a useful tool in
evaluating foods, especially for people who have insulin resistance.
The higher the glycemic
index, the more quickly blood sugar elevates after eating that food. Low
glycemic index foods have a glycemic index of 55. High glycemic index foods have
a glycemic index of 70 or more. This rating is all based upon glucose being
given an arbitrary value of 100. Low glycemic index foods are considered more
healthy because the energy released is slow and sustained, not quick,
stimulating a quick release of insulin that stresses the body.
Fast or Slow Carbohydrates?
There are times when
people need a quick source of fuel (those carbohydrates with a high glycemic
index). One of these times is when blood sugar is very low and needs to be
raised quickly. That's why it's important for people with diabetes, who often
have widely fluctuating blood sugar levels, to always have a quick source of
carbohydrate (like glucose tablets) to eat in case blood sugar levels fall too
low. Eating a quick source of carbohydrate (like hard candy) must be eaten
alone, because fat and protein will delay the absorption of the sugar. (That is
why a chocolate bar, which contains fat, is not a good choice at times like
Another good time to
choose high glycemic carbohydrate foods is when you want to quickly restore the
body's carbohydrate stores that are used up during intense exercise.
Slow carbohydrates are
generally the best choice for the everyday diet, to avoid rapid spikes in blood
sugar levels, especially if the body is insulin resistant because of extra body
fat. So, the glycemic index is typically used to help people choose low glycemic
index carbohydrates for the day to day diet.
Some Things to
The reason I do not use the glycemic index to plan your custom diet is that your
plan emphasizes choosing carbohydrates based upon their total nutritional value,
not just the blood sugar raising potential of the food. The glycemic index is
helpful, but is complicated for the average person to use correctly to plan a
healthy diet for these reasons:
glycemic index provides some very useful information, it should not be the
only measure of the value of the food. For example, a can of Coca-Cola has a
glycemic index of 63, while 5 dried dates has a glycemic index of 103. Which
is the more nutritious food? (Hint: not the coke!).
influence how quickly blood sugar is raised by a food include its chemical
composition, how long the food is cooked (to break down the carbohydrate
molecules, making them more quickly absorbed), and what other foods are
eaten with the food. For example, bread by itself might be quickly absorbed,
but bread and margarine takes longer to break down because of the presence
of fat. So, if you eat a food that has a high glycemic index along with some
fat or protein, it will change
how the food is absorbed and reduce the importance of the glycemic index.
Foods are not
typically eaten by themselves, they are eaten along with other foods, which
affect how quickly that food is digested. When you eat high glycemic foods
together with low glycemic foods, you can
average the effect.
In some cases, the
glycemic index of a food is based upon unrealistic amounts of foods. To get
55 grams of carbohydrate from bread, it takes about 3 1/2 average slices. To
get 55 grams of carbohydrate from carrots, it takes about 3 cups of carrots!
The glycemic index
helps us understand how specific carbohydrates affect blood sugar levels.
It is one piece of
information that can be helpful, but should not be used exclusively to
determine your diet.
A healthy diet, both
for weight loss and for weight maintenance includes a variety of
nutrient-dense carbohydrates – not junk foods!
The glycemic index
can be a little complex for most people to be very practical, but some may
find it helpful in evaluating foods.
Lastly, if you
really need to know how a carbohydrate affects your blood sugar (as in the
case of diabetes), you should test your blood sugar after eating the food,
following the instructions from your physician or your diabetes educator.
a sample of the author's diets today!
A Personal Dietitian