Take Very Good
Care of YourselvesDeuteronomy 4:15


 Glycemic Index Part 1

 By David Mendosa 

The glycemic index ranks foods on how they affect our blood glucose levels.

This index measures how much your blood glucose increases in the two or three hours after eating. The glycemic index focuses on the carbohydrates in foods; how quickly they break down and how quickly the glucose from these foods enters the blood stream. Foods high in fat or protein don't cause your blood glucose level to rise much.

The glycemic index is about the quality of the carbohydrates, not the quantity.  A lot of people still think that it is plain table sugar that people with diabetes need to avoid. The experts used to say that, but the glycemic index shows that complex carbohydrates, like baked potatoes, can be even worse.

When you make use of the glycemic index to prepare healthy meals, it helps to keep your blood glucose levels under control. This is especially important for people with diabetes, although athletes and people who are overweight also stand to benefit from knowing about this relatively new concept in good nutrition.

Recent studies of large numbers of people with diabetes show that those who keep their blood glucose under tight control best avoid the complications that uncontrolled diabetes can lead to. Most experts agree that what works best for people with diabetes—and probably the rest of us as well—is regular exercise, little trans fat (partially hydrogenated oils), and a high-fiber diet.

The recommendations to exercise and eat less trans fats is excellent advice—as far as it goes. The real problem is carbohydrates. The official consensus remains that a high-carbohydrate diet is best for people with diabetes. However, some of the experts, led by endocrinologists like Dr. Richard K. Bernstein, recommend a low-carbohydrate diet, because carbohydrates can raise blood glucose to dangerous levels But not all carbohydrates act the same. Some are quickly broken down in the intestine, causing the blood glucose level to rise rapidly. These carbohydrates have a high glycemic index Please note, however, that a GI value tells you only how rapidly a particular carbohydrate turns into glucose. It doesn't tell you how much of that carbohydrate is in a serving of a particular food. 

Four extensions of the glycemic index concept noted in the bibliography below address this limitation.

Advanced Glycemic Load Data: A correspondent named Ralph Brown, who is an Excel expert, took the new table of glycemic index and glycemic load values (at http://www.mendosa.com/gilists.htm) and added new dimensions to it. He calculated the glycemic load of all the foods per gram or ml and per ounce. He also ranked the glycemic load of foods overall and within their categories. Along the way he discovered nine internal inconsistencies in the new glycemic load calculations. Then I studied the data and found six more inconsistencies. I brought this information to the attention of the team at the University of Sydney in Australia that prepared the original table, and they corrected it. Subsequently, Hilary Ross added an index at the start to make it easier to navigate. Ralph's advanced data with Hilary's index is on-line at http://www.mendosa.com/GI_GL_Carb_data.xls.

The most important extension is called the glycemic load, which takes the quantity of available carbohydrates into account. Available carbohydrates are those that provide energy, i.e. starch and sugar, but not fiber. The glycemic load measures the effect of the glycemic index of a food times its available carbohydrate content in grams in a standard serving. 

Harvard School of Public Health professor and researcher Walter Willett, M.D., and his associates developed this concept as long ago as 1997, when they published journal articles on the subject. But it was only in their Harvard Women's Health Watch article and Dr. Willett's new book (see bibliography below) that they have published many of the GL numbers. For example, these resources have nice but very short lists of a few foods for which they have calculated the glycemic load (note in particular the high GI and low GL of watermelon). 

Selecting foods low in glycemic density allows us to naturally lower our blood sugar level. Before the development of the glycemic index beginning in 1981, scientists assumed that our bodies absorbed and digested simple sugars quickly, producing rapid increases in our blood glucose level. This was the basis of the advice to avoid sugar, a proscription recently relaxed by the American Diabetes Association and others.

Now we know that some simple sugars don't make your blood glucose rise any more rapidly than some complex carbohydrates do. Of course, simple sugars are simply empty calories, and still should be minimized for that reason.

Many of the glycemic index results have been surprising. For example, baked potatoes have a glycemic index considerably higher than that of table sugar A more pleasant surprise is the very low glycemic index of a tasty bean called chana dal,and ice cream. Hulless barley almost certainly has an even lower glycemic index than pearl barley, because pearling removes some of the fiber.

Scientists have so far measured the glycemic indexes of about 750 high-carbohydrate foods. The key is to eat little of those foods with a high glycemic index and more of those foods with a low index.

Where can you find what these foods are? The easiest way is to refer to http://www.mendosa.com/gilists.htm.

The GI is especially useful to people with diabetes who want to plan their diets to minimize the incidence of high blood glucose, or spikes. It measures how much of a rise in circulating blood sugar a carbohydrate triggers. The lower the number the less effect it has. The numbers are percentages with respect to a reference food. They are given here with respect to glucose. In other words, on the scale where glucose equals 100 multiply the GI on this scale by 1.4 to convert to the value on the scale where white bread = 100.

The satiety index, along with the glycemic index, are two of the most exciting tools that we have to control our diabetes Dr. Andrew Weil, the noted writer and lecturer on integrative medicine.

High glycemic foods like rice cakes, bread, and potatoes stress the body's insulin system and probably are chief culprits in obesity.

"We have worked out here that we should recommend a total GL of about 60 to 80 grams per day for people on a weight loss diet "Of course, the GI figures can't be added up like that, but we should encourage people to aim for an average GI of around 50 to 55. Continued in Part 2.

©Copyright Jewish Diabetes Association.  Last updated June 2017