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If you would discuss the glycemic index with almost any physician, nutritionist, or registered dietician, you would get a variety of different responses. The overwhelming majority of these health care professionals simply do not believe in the concept of the glycemic index and its inherent value to the health care of their patients. Most believe that a carbohydrate is a carbo- hydrate is a carbohydrate. In other words, all carbohydrates are the same and that the concept of simple sugar versus complex carbohydrates still prevails in the United States today. This concept is what is still taught to our diabetics in the US.
Carbohydrates are simply long chains of sugars that are attached together. Digestion rate, and
thus the rise in blood sugar after eating a particular carbohydrate are commonly thought to be
determined by the length of this sugar chain. This concept was first introduced in 1901, and has
prevailed throughout the entire 20th century and now into the 21st century. It has been felt that
if you eat a simple sugar like glucose or sucrose, your blood sugar would rise rapidly because
the body does not need to break down the sugar. However; if you eat a complex carbohydrate
like a potato or a piece of bread, your blood sugar would rise slower, and therefore, be better for
the diabetic and normal person. This is why you see simple sugars, candy, and sweets at the peak
of the USDA food pyramid. This concept of simple sugar and complex carbohydrate has been the
standard of care now for well over the past 100 years and has been firmly imbedded in our
thinking and our practice of medicine. It is hard to change a concept that has been with us for so
long. However, as you will learn, it is the main reason we are facing such a health care crisis in the
As the concept of a low-fat, high-carbohydrate diet gained acceptance in the early 1970's, the basic recommendation was that any carbohydrate other than sugar was acceptable in this newly recommended "healthy" diet. There was no distinction made between the different characteristics of these complex carbohydrates and the focus was primarily on teaching everyone to decrease the amount of fat that they were consuming in their diet. It was this reliance on a 1901 theory that was the primary reason that we are facing this overwhelming problem with both obesity and diabetes in the Western world today.
The concept of the glycemic index was introduced in 1981 by Jenkins in the American Journal of
Clinical Nutrition. Glycemic index is defined as the rate blood sugar would actually rise following
the ingestion of a particular test food relative to the ingestion of a standard food (either white
bread or glucose). Therefore, the glycemic index of a specific food or meal is determined primarily
by the nature of the carbohydrate or carbohydrates consumed and by other factors that affect the
digestion of that particular meal (including the fat and protein content of that meal). This concept
has totally changed the way we look at carbohydrates. Instead of totally accepting the theory that
the rate of absorption and thus the rate of rise of the blood sugar is simply based on the length and
complexity of the sugar being consumed, the actual and true rise of the blood sugar was determined
in a clinical setting with standardized techniques.
Most of the confusion with the glycemic index in the health care community and with patients is due to the use of two different standards (white bread and glucose) over the past 20 years. In other words, some of our clinical studies dealing with the glycemic index used white bread as the standard and some of our studies used glucose. When glucose is used as the standard, white bread has a glycemic index of 70. When white bread is used as a standard it has a glycemic index of 100.
Therefore the glycemic index numbers for different carbohydrates will be different based on which standard food-either glucose or white bread-was used. I believe that the standard food that will prevail is going to be glucose=100. Therefore, in the Healthy for Life Program, I will refer to all of the foods according to the standard where glucose equals 100. It is possible to convert the glycemic index from the standard of white bread to glucose by using the factor of 0.7.
When this concept was first released, most dieticians, nutritionists, and physicians were shocked by
the results. For example, simple sugars like table sugar (sucrose) had a glycemic index of 61 and the
sugar found in fruits (fructose) had a glycemic index of 19. This was in contrast to some complex
carbohydrates like white potatoes, which had a glycemic index of 85 or white bread that had a
glycemic index of 70. Even more concerning was the fact that wheat bread had a glycemic index of
77 and breakfast cereals like corn flakes, bran flakes, and Cheerios had a glycemic index which was
very high and some as high as 92. This literally shot the concept that the rise in blood sugar could
be determined solely on whether a carbohydrate was a simple sugar or a complex carbohydrate in
the foot. Obviously, the majority of health care professionals did not accept this new concept with
For years the concept of the glycemic index has been very controversial. There have been many heated discussions at conferences where these two concepts have been discussed. Obviously, it takes time to have a paradigm shift; especially, when it comes to a concept that has been the mainstay of diet counseling for the past century. Studies done in Australia, Canada, United Kingdom, and across Europe have now proven beyond any doubt there is tremendous value in the glycemic index. How- ever, the United States remains opposed to this new concept and continues to recommend teaching the concept of simple sugar and complex carbohydrates to everyone including our diabetics. How- ever, there is no doubt in my mind that after reviewing the medical literature regarding the glycemic index that the US will soon follow and accept the concept of the glycemic index. In fact, in the May 8, 2002 issue of the Journal of the American Medical Association an article was presented that reviewed 311 of these studies dealing with the glycemic index.
Since we are now realizing that simple sugars and complex carbohydrates no longer give us any indica- tion on how fast we will absorb these foods, what really determines our body's ability to absorb a particular food? In a nutshell, it is how a particular carbohydrate has been processed and prepared. Since 90% of the carbohydrates we now consume in the United States and many other parts of the world are processed carbohydrates, you are going to begin to understand why obesity, heart disease, high blood pressure, elevated lipids, and diabetes are epidemic in the Western World today. In fact, you will also begin to realize the main answer in helping solve our present health care crisis---going back to the basics and learning to eat again the "Old Fashioned Way".
We live in an era of the "instant". Instant potatoes, instant rice, instant oatmeal, etc. are simply a way of
life. We rush to work in the morning grabbing a piece of toast (usually made from white flour or wheat
flour), a glass of orange juice, and a 12-ounce cup of coffee on our way out the door. For lunch, we stop
by our favorite fast food restaurant and become impatient when our hamburger fries, and coke (super-
sized) is not ready within two minutes. After a long day at the office for both husband and wife a quick
call is made on their cell phones to decide which one is going to pick up the pizza for dinner that night.
Does this sound all too familiar?
The fast food, instant food, and consumption of highly processed foods is the most dramatic change that has occurred in our society over the past two generations. The health consequences of this change are not just devastating but lethal. When you look at the list of the sources of the top 20 carbohydrates in our diets today compiled by a researcher at the Harvard School of Public Health, you begin to realize that the scenario presented above is right on target.
When you look at the glycemic index of these various foods, you soon begin to realize that the
majority are very high-glycemic. Much of this is due to the fact that these foods are highly
processed and are made with our modern-day flour. Modern flour comes from high-speed rolling
mills, which replaced the traditional millstones of the 18th century. The new mills were much
more efficient; however, because they generated much more heat, the flour would spoil very
quickly. This was primarily due to the oxidation of the embryo of the seed which occurred much
more quickly because of the high heat that was produced.
Well, it did not take them very long to realize that if they would degerminate the grain and also remove the seed coat (called the bran) whose fiber impeded the new milling process so that this oxidation process could be avoided. The result was superfine, pure white flour, which did not spoil. It was an economic coup. Not only was the bread, bread products, and pastries made from this flour light and tasty but it also had an extra-long shelf life. It soon became a delicacy of the rich; while the old, stone-ground flour with its coarse texture and taste was left to the peasants of the world. However, as we are now beginning to realize our body is able to absorb these very superfine particles of white or wheat flour very quickly. This results in a rapid rise of our blood sugar and creates a very high-glycemic index. In fact, as noted earlier, white bread and white flour spikes our blood sugar faster than if we were slapping table sugar on our tongue.
Just think about the amount of processed grains and carbohydrates that are in our diet. White bread, white flour, wheat flour, most rice, cakes, donuts, potato chips, breakfast cereals, fruit juices, sodas, sports drinks, and the list goes on and on.
Now take a look at the glycemic index of whole foods. Whole foods are defined as those foods that are eaten in their natural state. In other words, they are not processed and many of these foods are referred to as live foods. Some examples of whole foods are apples, oranges, grapes, beans, cauliflower, brussels sprouts, oats, and whole wheat grains. These foods are natural and still contain their natural fiber and natural form. When you check out these foods on the glycemic index chart, you will find that they are all low-glycemic foods. Therefore, a general principle, however not an absolute principle, is that the more highly processed a food is the higher its glycemic index.
In general, the higher the fiber content of a particular food the lower the glycemic index. How- ever, according to Thomas Wolever, one of the leading authorities in the glycemic index, although it is helpful to know the type and quantity of fiber in various foods it is not the only factor that determines the glycemic index. For example, the fiber found in processed white or wheat flour does nothing to slow down the absorption of these carbohydrates. However, when you consider the viscous fiber found in legumes and whole oats, it definitely slows down the absorption of the carbohydrates from these foods. In general, Wolever states that in the purified form soluble fibers have a greater affect on the glycemic response when compared with insoluble fibers. However, it is still difficult to determine the glycemic index of a food by simply looking at its fiber content.
There are two types of starches that make up many of our foods. These are called amylose and amylopectin and the ratio with which these two starches occur in our foods has a strong influence on the glycemic index. Amylose is a straight-chain molecule that lines up like a tight set of beads. This configuration makes it hard to gelatinize and therefore much more difficult to digest. On the contrary, amylopectin is made up of linear molecules with many branches. This allows it to be digested quite easily. These two starches occur in various foods at different ratios. Those foods containing a high percentage of amylopectin obviously turn out to be high-glycemic. These are typical of many of the rice dishes available. However, those foods that have a higher level of amylose, such as basmati rice, black beans, lentils, and soy beans are very low-glycemic.
One of the most surprising aspects of the glycemic index is the wide variation in how various
natural sugars are absorbed. For example, the sugar primarily found in fruits (fructose) has a
glycemic index of 19, while glucose has a glycemic index of 100. Most people do not realize that
table sugar (sucrose) is a disaccharide (made up of two molecules), which means that it is a double
sugar made up of one molecule of glucose and a molecule of fructose. This is the reason that table
sugar has a glycemic index of 61, which is basically in the middle between the two sugars that make
up sucrose. Honey has a glycemic index of 55. Lactose (the carbohydrate found in milk) has a
glycemic index of 46 while maltose has a glycemic index of 105.
It doesn't take much to realize that the glycemic index of various foods will be determined in a large part by the type and amount of sugar that is present. However, there is still a wide variation in different types of fruits. The tropical fruits like bananas, mango, and pineapple have a medium- glycemic index, while most of the other fruits (other than watermelon) have a low-glycemic index. Many of the higher processed foods like most yogurts actually have a mixture of natural and added sugars and therefore, tend to have higher glycemic indexes.
Usually the starch in raw foods is stored in hard, compressed granules that make them very difficult
to digest. This is why you will see that almost all raw foods have a lower glycemic index than the
cooked foods of the same type. The reason this happens is because during cooking these hard,
compact starches expand when they are heated and may actually burst. This is a process called
gelatinization. These swollen starches are very easy to digest and be absorbed by the starch
digesting enzymes of the small bowel. This is why you do not want to overcook any of your food.
Heat is not your friend when it comes to the glycemic index of your foods. You will later learn
that it can turn good fats into bad fats and in this situation, turn low-glycemic carbohydrates into
higher-glycemic carbohydrates. For example, you want to basically undercook most of your
pasta so that it remains firm (al dente).
Needless to say, trying to determine the actual glycemic index of foods based on their fiber, sugar, and type of carbohydrates is guess work at best. Although it is safe to say that most whole fruits, whole grains, and whole vegetables are going to be significantly lower in their glycemic index than are the more highly processed foods.
Since the concept of glycemic index is relatively new to most people, there is always some confusion
about how exactly to interpret its practical use as a guide to healthy nutrition. One of the major
reasons that you want to become familiar with the glycemic index of most common foods is because
it is critical to avoid the problem of spiking your blood sugar and subsequently our blood insulin
levels following a meal. In order to better understand its use, you need to learn about the concept of
Glycemic load is defined as the weighted average glycemic index of individual foods multiplied by the percentage of dietary energy as carbohydrates (grams of carbohydrates or calories) that particular food contains. A simple calculation allows you to arrive at the glycemic load of any food. You can usually locate the grams of carbohydrate a particular food contains by looking at the food label or using a food composition table and then multiplying it by the glycemic index found at the back of this book. Then divide this number by 100.
Glycemic Load = (Glycemic Index x Grams of Carbohydrate per serving) divided by 100. Rice: 1 cup of cooked instant rice has a GI value of 87 and contains 37 grams of carbohydrate Glycemic load: (87 X 37) divided by 100 = 32 Apple: Apples on an average have a GI value of 38 and the contain 16 grams of carbohydrate per serving Glycemic load: (38 X 16) divided by 100 = 6
This concept of glycemic load gives you a much better picture of the glycemic response a particular food will have. For example, cooked carrots have a medium glycemic index of 49 while its glycemic load is 3.8 (there are simply very few calories in carrots). This simply means that carrots do not contain enough carbohydrates to spike your blood sugar even though they have a medium glycemic index (GI). However, potatoes have both a high glycemic index and a high glycemic load, which will significantly raise your blood sugar and stimulate your insulin response.
One of the major arguments against using the glycemic index in clinical medicine stems from the
argument that when you mix your carbohydrates, fats, and protein together into a regular meal, all
carbohydrates are still absorbed at the same rate. Initially, there were a few studies that actually
supported this viewpoint. There is no doubt that fat will slow down gastric emptying, which slows
down digestion and therefore lowers the glycemic index of a mixed meal. In fact, this has become
another major concern with the low-fat, high-carbohydrate diet. As individuals began eating more
and more carbohydrates in their diet, they also were eating less and less fat. This caused even
greater spikes in their blood sugars following these meals.
Protein takes much longer to digest than most of your carbohydrates. Following a meal or snack that contains a significant amount of protein there will definitely be a slower rise in your blood sugar. This is the reason that when you eat protein in a meal or snack you are more satisfied for a longer period of time. However, over the years, more and more studies showed that when you looked at the glycemic index of various foods in a particular meal, you were able to accurately predict the glycemic and insulin response to that meal. These studies showed that even the addition of fat and protein to the meal did not significantly change the overall glycemic response expected by the types of carbohydrates the meals contained. Additionally, when two carbohydrates were mixed together in equal proportions in one meal, the blood glucose response was approximately midway between those meals containing each food alone.
The glycemic index is only one consideration in choosing the types of foods you are going to eat. For
example, sugar, some soft drinks, and some sweets are mid-glycemic. However, their poor nutritional
value and glycemic load are not ideal for a healthy diet. It is critical that you learn the greatest enemy
is processed carbohydrates. You will also learn that there are good fats and bad fats as well as good
proteins and bad proteins. However, you hopefully gained an appreciation for the fact that in this
modern, fast paced world, you need to understand the underlying dangers to the instant, fast food
I would encourage you to now spend some time reviewing the recommended carbohydrates, fats, and proteins. This list of foods has been divided into the most desirable, moderately desirable, and least desirable carbohydrates, fats, and proteins. The glycemic index, types of fats and protein a particular food contains was taken into consideration before placing them in these various categories. It is important that about 70% of your food choices come from the desirable list, 20 to 25% of your food choices come from the moderately desirable list, and only 5 to 10% of your food choices come from the least desirable list.