Take Very Good
Care of YouselvesDeuteronomy 4:15


The Glycemic Index
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 is about foods high in carbohydrates. 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 this disease 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). Now, however, Jennie Brand-Miller and her associates at the University of Sydney have calculated the GL of all 750 foods for which GI numbers have been calculated. This table was published originally in the July 2002 issue of the American Journal of Clinical Nutrition, and I publish an extract of that table on a Web page on this site as authorized by Professor Brand-Miller. She also published the table in the new version of her book, The New Glucose Revolution, (Marlowe, January 2003). That table is also a part of What Makes My Blood Glucose Level Go Up...And Down, which I wrote with Professor Brand-Miller and Kaye Foster Powell (Marlowe, August 2003)
Des Buchhorn similarly developed the adjusted carbohydrate exchange, which refines carbohydrate exchange lists by multiplying the glycemic index of a food by its carbohydrate content to indicate the likely effect of a food on blood glucose

J.A. Monro, a scientist at the New Zealand Institute for Crop & Food Research, developed the concept of relative glycemic potency, which compares equal weights of foods

Derek Paice, an engineer who has type 2 diabetes, similarly developed the concept of the substance glycemic index based on a fixed weight of foods. Derek published his experiments and findings in a 32-page booklet, "Diabetes and Diet: A Type 2 Patient's Successful Efforts at Control." He has authorized me to make the book freely available (in PDF format) at http://www.mendosa.com/DiabetesAndDiet.pdf

Rich Price developed the Glycemic Matrix to utilize the principle of glycemic density. This is a measurement of the glycemic load in a gram of food. Some researchers think that we tend to eat by food weight and not by calories. Selecting foods low in glycemic density allows us to naturally lower our blood sugar level. The URL isÃÜ
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 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 surprises. 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, which is the subject of a separate Web page that I maintain at http://www.mendosa.com/chanadal.html

Hulless barley almost certainly has an even lower glycemic index than pearl barley, because pearling removes some of the fiber. A great source of hulless barley that I have used for years is Bob's Red Mill Natural Foods Inc. in Milwaukie, Oregon, phone (503) 654-3215, e-mail jodi@bobsredmill.com

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 another Web page that I maintain. That page at http://www.mendosa.com/gilists.htm summarizes the academic research on this important dietary concept

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

Other Resources

Listings of thousands of foods for their glycemic index and glycemic load follow on a separate Web page. That is so this page won't be so long. Please click on the link at http://www.mendosa.com/gilists.htm for these listings

New editions of the ultimate book about the glycemic index appeared in the UK and Australia in 1998. It has now been published in the U.K. and the U.S

The first North American edition of the book appeared in July 1999, and third edition came out in 2007. Now titled The New Glucose Revolution: The Authoritative Guide to the Glycemic Index, this 347-page book lists for $16.95 and is published by Marlowe & Company in New York. The North American co-author with Jennie Brand-Miller and her team at the University of Sydney is Thomas M.S. Wolever, M.D., Ph.D., of the University of Toronto, the world's other leading active glycemic index researcher

The book includes more than 50 recipes and the glycemic index and glycemic load for many foods and beverages. The authors explain the benefits of a diet that emphasizes foods that are low on the glycemic index. These are foods that as they are digested produce a low, slow blood-sugar response

The book has some very positive endorsements. Here's one example. "Forget Sugar Busters. Forget The Zone," writes Jean Carper, best-selling author of Miracle Cures, Stop Aging Now!, and Food: Your Miracle Medicine. "If you want the real scoop on how carbohydrates and sugar affect your body, read this book by the world's leading researchers on the subject. It's the authoritative, last word on choosing foods to control your blood sugar

If you are trying to lose weight—something of great interest to many people with type 2 diabetes—you may also want to study my Satiety Index page at http://www.mendosa.com/satiety.htm. 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, has come out strongly for the utility of the glycemic index. See "What's Up with The Zone?" at http://cgi.pathfinder.com/drweil/. He writes that "we should pay attention to the glycemic index of carbohydrate foods—that is, the ease with which the body converts them to blood sugar. High-glycemic foods like rice cakes, bread, and potatoes stress the body's insulin system and probably are chief culprits in obesity

What about Portion Size? And how is GI Determined

The glycemic index is about the quality of the carbohydrates, not the quantity. Obviously, quantity matters too—and that is the reason for the glycemic load values—but the measurement of the glycemic index of a food is not related to portion size. It remains the same whether you eat 10 grams of it or 1000 grams. That's because to make a fair comparison tests of the glycemic indexes of food usually use 50 grams of available carbohydrate in each food. You can eat twice as many carbohydrates in a food that, for example, has a glycemic index of 50 than one that has a glycemic index of 100 and have the same blood glucose response

Basically, test foods are fed to various people, some with diabetes, others without, in portions that contain 50 grams of available carbohydrates. The 50 gram carbohydrate portion is specified in Dr. Wolever's methodology paper (see bibliography below) as 50 grams of available carbohydrates. "That means it excludes the fiber," Professor Brand-Miller writes me. "We have always used a 50 gram available carbohydrate portion and often relied on manufacturers to give us the composition data. I am aware of only one instance where we been given incorrect information and therefore inadvertently included the fiber in the 50 gram carbohydrate portion…but there may be some papers from developing countries where the data is not reliable

For example, to test boiled spaghetti, the scientists give their subjects 200 grams of spaghetti, which according to standard food composition tables provide 50 grams of available carbohydrate. The scientists compare this response with the volunteer's response to a reference food, which may be either glucose or white bread. Both for the test and for the reference foods the volunteer's response over the next two or three hours is calculated. Rather than measuring a single point, they make the more precise measurement of the area under the curve. Then, they repeat the whole process on different days to reduce the effect of day-to-day variations

Next, the area under the response curve for the test food is expressed as a percent of the mean value for the reference food for the same subject. Finally, these percentages from each subject are averaged together to obtain the GI for that food. For more information, see Wolever, Thomas M.S. et al. "The Glycemic Index: Methodology and Clinical Implications," listed in the bibliography below

What Daily Maximums Should We Set

Here is what Jennie Brand-Miller told me about daily maximums

"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 article 2