The Glycemic Index Still Matters for Diabetes

by David Mendosa Patient Advocate

The glycemic index is about foods that are high in carbohydrates, and the easiest way to manage our diabetes is a very low-carb diet. But low-carbing is basically taking the glycemic index one step further.

A low-carb diet isn't a no-carb diet. In fact, the glycemic index is as important for those of us who eat 50 or fewer grams of carbohydrates a day as for people who use insulin or pills.


At the end of 2007 I switched from relying on pills and the glycemic index when I decided that a very low-carb diet was safer than using medicine, which always has side effects. Before then, my first book was about the glycemic index. I co-authored What Makes My Blood Glucose Go Up...and Down? together with the world's top glycemic index scientist, Professor Jennie Brand Miller of Australia's University of Sydney, and her associate Kaye Foster Powell.

Starting in 1996 I had worked with Dr. Brand Miller, when I wrote the first article in the North American lay press about the glycemic index. My article in the August 1996 issue of Diabetes Interview magazine reviewed her first book, The GI Factor, which she had published in Australia and New Zealand. Later, I introduced her to the publisher of Avalon Publishing Group, which brought out a best-selling series of her books about the glycemic index in North America, including the one that I co-authored with her.

In my 20-year journey with diabetes I tested many diets, including one that was very high carb, The McDougall Plan. While I decisively turned my back on that one, I know that the glycemic index makes scientific sense. I keep it in mind when I choose which carbohydrates to eat.

For example, one of the reasons why I eat blueberries instead of bananas is that blueberries are lower glycemic. You can find an extensive list of those foods that scientists have tested on my website at "Revised International Table of Glycemic Index (GI) and Glycemic Load (GL) Values -- 2008."

But now my concern is that the initial enthusiasm for the glycemic index has waned. Ten or 15 years ago it was the hottest topic on my website, Now, I rarely get any questions about it.

Part of the problem may be confusion as to whether to pay attention to the glycemic index or the glycemic load of foods.

The glycemic index is a numerical system of measuring how much of a rise in circulating blood sugar a carbohydrate triggers -- the higher the number the greater the blood sugar response. So a low GI food will cause a small rise, while a high GI food will trigger a dramatic spike. Pure glucose, the sugar that causes the greatest spike in our blood, is set at 100 and is the basic of the index. We consider a GI of 70 or more to be high, a GI of 56 to 69 to be medium, and a GI of 55 or less to be low.

The glycemic load is a newer way to assess the impact of carbohydrate consumption. It takes the glycemic index into account, but gives a fuller picture than does glycemic index alone. A GI value tells you only how rapidly a particular carbohydrate turns into sugar. It doesn't tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food's effect on blood sugar.

The carbohydrate in watermelon, for example, has a high GI. But there isn't a lot of it, so watermelon's glycemic load is relatively low.

A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low. Still, foods that have a low GL almost always have a low GI. Foods with an intermediate or high GL range from very low to very high GI.

The major problem with the GL is that it's based on a serving size, and a serving size is arbitrary. That's a big reason why, like most people, I pay attention to the GI much more than I do to the GL.

Perhaps the biggest problem for most people with both the GI and GL is that it seems complicated. In large part that's because it has to include so many foods that people around the world eat.

For simplicity I put together a much shorter webpage about "The Glycemic Values of Common American Foods." I'm hoping that many more people who have diabetes can use this table to help manage their blood sugar whether or not they follow a very low-carb diet.

David Mendosa
Meet Our Writer
David Mendosa

David Mendosa was a journalist who learned in 1994 that he had type 2 diabetes, which he wrote about exclusively. He died in May 2017 after a short illness unrelated to diabetes. He wrote thousands of diabetes articles, two books about it, created one of the first diabetes websites, and published a monthly newsletter, “Diabetes Update.” His very low-carbohydrate diet, A1C level of 5.3, and BMI of 19.8 kept his diabetes in remission without any drugs until his death.