The Glycemic Index: Is it effective?

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The Glycemic Index: Is it effective?

Postby dlcnurse » Thu Mar 15, 2007 11:25 pm

Over the past two decades low glycemic index diets have been reported to improve glycemic control in diabetics, to reduce serum lipids in hyperlipidemia, and possibly to aid in weight control.

In large cohort studies, low glycemic index or glycemic load diets have also been associated with higher levels of high-density lipoprotein cholesterol, reduced C-reactive protein concentrations and with a decreased risk of developing diabetes and cardiovascular disease.

More recently, some case-control and cohort studies have also found positive associations between the dietary glycemic index and the risk of colon, breast, and other cancers.

While the glycemic index concept continues to be debated and there remains inconsistencies in the data, sufficient positive findings have emerged to suggest that the glycemic index is an aspect of diet of potential importance in the treatment and prevention of chronic diseases.

Now that we have the scientific portion out of the way, you are saying well, "I still don't know what the purpose of the glycemic index is."

The aim of the glycemic index classification of carbohydrate foods was to assist in the physiological classification of carbohydrate foods which, it was hoped, would be of relevance in the prevention and treatment of chronic diseases such as diabetes.

what is the glycemic index?

The glycemic index is a numerical index that ranks carbohydrates based on their conversion to glucose within the human body. Glycemic Index uses a scale of 0 to 100, with higher values given to foods that cause the most rapid rise in blood sugar. Pure sugar serves as a reference point and is given a value of 100.

So, you are saying I am not a diabetic so why is it important for me?

Your body performs best when your blood sugar is kept relatively constant. If your blood sugar drops too low, you become lethargic and/or experience increased hunger. And if it goes too high, your brain signals your pancreas to secrete more insulin. Insulin brings your blood sugar back down, but primarily by converting the excess sugar to stored fat.

Therefore, when you eat foods that cause a large and rapid glycemic response, you may feel an initial elevation in energy, and mood as your blood sugar rises, but this is followed by a cycle of increased fat storage, lethargy, and more hunger.

Although increased fat storage sounds bad enough, those with diabetes have an even worse problem because their bodies inability to secrete or produce insulin causes their blood sugar to rise too high, leading to a host of additional medical problems.

You are asking, should all high Glycemic Index foods be avoided??

There are times when a rapid rise in blood sugar may be desirable. For example, after strenuous physical activity, insulin also helps move glucose into muscle cells, where it aids in tissue repair. So, your activity needs to be taken into consideration when determining the amount of carbohydrates you need for your body to respond as it should and speed recovery of muscle cells.

What else do I need to take into consideration when considering the glycemic index?

You also need to take into the consideration of the amount of food you are consuming which also leads to a rise in blood sugar. The concept of glycemic index combined with the total intake is referred to the "Glycemic Load" A really good site that discusses glycemic load is ... -load.html

Okay, so how does it work?

Lets take candy. Although most candy has a relatively high glycemic index, eating a single piece of candy will result in a relatively small glycemic response. Why? Well, simply because your body's response is dependent on both the type and the amount of carbohydrate consumed.

You, therfore, can control your glycemic response by consuming lower glycemic foods and by restricting your intake of carbohydrates.
The glycemic load is calculated this way:
Glycemic Load = Glycemic Index divided by 100 multiplied by the net Carbohydrates. (Net carbs are equal to the total carbohydrates minus the dietary fiber).
You can also use the average of the Glycemic Index value by the amount of carbohydrates per serving and divide by 100. Which is much simpler to use since most tables do not give you the glycemic load values.

So how do I know what is a low, medium, or high glycemic index?
low = 55 or less
medium = 55 to 70
high = 70 or above.

To give you a few examples of foods, here are a few:
Food GI Serving size net carbs GL
Peanuts 14 4 oz 15 2
Grapefruit 25 1/2 large 11 3
Pizza 30 2 slices 42 13
Lowfat 33 1 cup 47 16
Apples 38 1 medium 16 6
Potato chips 54 4 oz 55 30
White Bread 70 1 slice 14 10

These are just a few on the list. You can view a more complete list at: You can also do a search on this site for specific foods that will give you the glycemic index for those foods.

For those who what a more extensive list you can find it here: which should take you directly to the table. This is found in the American Journal of Clinical Nutrition Vol 76, No 1, 5-56, 2002.

Another site that you can view a revised copy of the International Glycemic Index can be located at this site. This is a site by David Mendosa and he has some excellent resources as well on his site. The index is printable from his site but you may need to correct the margins. If you read the page downward, you will come to the index itself. You can also view and download a 26 page index here:

So are there limitations to the Glycemic Index and Glycemic Load?
Unfortunately, yes. For starters, there is a scarcity of data on the Glycemic Index. Although methods for determining glycemic index has been in existence for more than 20 years, Glycemic values for most foods are not available. The most extensive list was done in Sydney, Australia.
(I do currently have a copy of the list if you would desire a copy of it, please let me know).

Secondly, there are wide variations in the Glycemic Index measurements. Most lists will give you a single number but in reality, though, the measurements are not that precise. Reported values are generally the averages of several tests. Which there is nothing wrong with the methodology, but individual measurements can vary significantly, depending on the method of cooking, the ripeness, and type of food consumed.

The glycemic index value is affected by the combination of other foods eaten, such as fiber, proteins, or fat will generally reduce the glycemic index. This is considered what they term a "mixed meal". But all is not lost here. The glycemic index can be estimated by taking a weighted average of the GI's of the individual foods in the meal.

The rate of the glycemic response also can vary from individual to individual, depending on their own bodies responses to the activity level, the insulin response, and also on the time of day.

Using the glycemic index alone can lead to overeating!
Let me give an example here:
You have two choices, a medium sized apple and a 4 oz bag of peanuts. Looking at the glycemic index, the load you see that the peanuts has a much lower glycemic index (14, net carbs of 15 and a load of 2) you look at the apple and see that it has a glycemic index of 38, 16 net carbs and a load of 6, but is the peanuts truly the better choice of foods? NO. Take a look at the amount of calories in these two items.. the peanuts have 500 calories in them! With the apple with only 72 calories... those extra 400 calories are not going to help those of you wanting to lose weight.

Now that we have seen some of the pitfalls of the glycemic index, you are still asking yourself.. is this worth it???

As you consider the strengths and weaknesses of the glycemic index, it's important to not lose sight of the orignal goal. What you are really trying to do is control blood sugar levels. So, is the glycemic index the only way you can do this? NO. Watching the amount of carbohydrates you eat at each meal can also control the way sugars are absorbed and used in your body.

So is it effective? Yes. The glycemic index is a tool to assist you. It is not intended to use alone to control diet, blood sugars, and carbohydrate intake. Used appropriately, it is effective in healthy eating for the non-diabetic person or the diabetic person.

Eating a healthy, maintained diet with the use of paying attention to the amount of carbohydrates, using the glycemic index as a tool to assist you, watching trans fat intake, lowering the caloric intake are all methods of maintaining an optimal steady state of health and diet.

Always ask your doctor what is best for you individually before starting any type of diet, it is very much individualized depending on your own lifestyle, health status, stature, and body weight.

Learning to eat healthy requires both you, your doctor, and famiy support systems. Educate yourself before taking on any kind of diet, food craze, or changing your lifestyle.
Last edited by dlcnurse on Thu Aug 18, 2011 3:32 am, edited 1 time in total.
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