There are many different diets circulating in the media as well as medicine today. Diets that focus on reduced carbohydrate intake, diets that limit or reduce fat intake, low-caloric diets, combination diets, blood typing diets, genotype diets, and diabetic diets can all be very confusing.
The topic of this discussion is the glycemic index. The glycemic index was first developed by Dr. David Jenkins who was a professor of nutrition at the University of Toronto in Canada. The first glycemic index was developed in 1981 by Dr. Jenkins. The purposes of determining glycemic index of particular foods were to determine which foods were best for people with diabetes. In the early 80s, most dietary programs that focused on diabetics were based on systems of different carbohydrate exchanges. Each exchange or each portion of food one was able to consume contained the same about of carbohydrate. The exchange system assumed that all starchy foods produce the same effect on blood glucose levels. Even though some earlier studies had also proven this was not correct, it was during that time that the phrase "good carbs and bad carbs" was developed and as time went on, we started to understand there were simple carbohydrates and complex carbohydrates and as time continued to go on, we realized that they had different effects on blood sugar levels, so in reality all carbs were not the same.
Dr. Jenkins was one of the first researchers to challenge the use of these exchanges and the first to really study the effect foods have on blood sugar levels as well as blood insulin levels. Dr. Jenkins' approach was very scientific in nature which for the time was very unusual especially when trying to ascertain the effects different foods had on blood sugar level. Dr. Jenkins and his fellow researchers tested a large number of common foods with some very surprising results. For example ice cream which is greatly loaded with sugar content had less effect on blood glucose than ordinary white bread did, so basically the testing of individual food groups revealed surprising results in terms of affecting blood glucose levels, so Dr. Jenkins was actually a pioneer in developing a new means of classifying different types of carbohydrates.
His classification is known as the glycemic index, so what exactly is the glycemic index? The glycemic index is a means of ranking different food groups based on their immediate affect on blood sugar level. The foods that primarily affect blood sugar level are the carbohydrates. Proteins and fats do have an effect on blood glucose levels but not to the same degree that carbohydrates do, so for this reason carbohydrates were the primarily studied classification of food groups. For the comparison to be equal, all foods are compared with the reference food such as pure glucose in equivalent carbohydrate amounts so the basic standard is sugar and sugar is given a value of 100. All foods tested and given a glycemic index number and are compared to sugar. It was believed at that time, if we were aware of the impact of food on glucose levels, we could, by manipulating the foods we intook affect blood glucose levels, thereby normalizing and stabilizing blood sugar levels and in effect controlling diabetes. As a practical example and again glucose having a value of 100, potato chips have a glycemic index of 57, jelly beans which contain a great deal of simple sugar has a glycemic index of 80, peanuts on the other hand have a glycemic index of 7, tortilla chips or corn chips have a glycemic index of 42.
Again, all these are relative to glucose being 100 on the glycemic scale. As with most new discoveries in medicine or in scientific research, when new ideas are presented there is a great deal of controversy surrounding the theories and only over time and pending proven scientific results has the glycemic index now been accepted as the standard for measuring carbohydrate and their influence on blood sugar levels.
Other researchers over the past several years that have been involved in research considering glycemic index, include Dr. Jennie Brand Miller from the University of Sydney as well as Dr. Thomas M.S. Oliver and his colleagues at the University of Toronto. Foods containing carbohydrates that break down quickly during digestion have the highest glycemic index values. In other words, the glucose or sugar in the blood stream increases rapidly. Foods that contain carbohydrates that break down slowly release glucose gradually into the blood stream. These foods have a low glycemic index value. High glycemic index foods cause very wild, erratic elevations in blood glucose level and consequently reducing levels of glucose quickly in the blood stream. On the other hand, low-glycemic index foods are the slow and steady, low GI foods produce a smooth blood glucose curve without wild fluctuations. High glycemic index foods are useful in the treatment of hypoglycemia of short periods of time. Oftentimes after athletic competition or extreme physical exertion, high glycemic index foods are indicated again short term to reduce recovery time in these individuals.
As I previously noted, the glycemic index of pure glucose is set at 100 and the other food is ranked on the scale from 0 to 100 according to the actual effect on blood glucose levels. There are several foods that actually have a glycemic index greater than 100. These would include white flour and jasmine rice as well as a few others. The reason for this is that these types of foods unlike glucose are held in the stomach longer for digestion consequently altering the glycemic index and the effect of the glucose on the blood stream.
In summary, the glycemic index is a measure of the immediate affect of a food on blood sugar level. Glucose is the standard with a glycemic index of 100. All foods are ranked on a scale of 0 to 100.
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About the Author:
Dr. Lewis provides science based nutritional counseling utilizing whole food vitamins, minerals, homeopathics, and herbal remedies. Diagnostic testing is a key component in the evaluation process.
Dr. Keith E. Lewis, B.S.D.C. D.A.B.A.A.H.P., F.A.A.I.M. http://www.freehealthstrategies.com