After 30 Years, Glycemic Index Still Fights for Acceptance
In Australia, if you pick up a box of Lean Cuisine's chicken pomodoro you'll find a small blue and white symbol on the label that lists the product's glycemic index in addition to the usual facts about calories, carbohydrates, fat, protein and sodium. Some 150 other product carry the symbol, too.
Developed nearly 30 years ago at the University of Toronto, the glycemic index (GI) is becoming part of the nutritional landscape Down Under. And it's attracted attention here, too, among nutrition researchers and writers like me interested in understanding more about how our bodies process food.
The glycemic index tries to gauge how much your blood sugar is likely to rise after eating a particular food. The higher GI score of a food, the more it raises blood sugar -- something people, especially those with diabetes, need to avoid. Foods with scores of 70 to 100 are considered high-glycemic; those with scores of 55 or below are labeled low-glycemic.
In recent years, the glycemic index has been popularized by Jennie Brand-Miller, a professor of nutrition at the University of Sydney and the best-selling author of "The New Glucose Revolution" and 15 other books that collectively have sold more than 3 million copies. Brand-Miller says that eating according to the GI has numerous health benefits and is important both for those who have diabetes and for those who want to avoid it.
The widespread concept of the GI often gets boiled down to this: Skip foods with added sugar or processed white flour. But it's not that simple.
Take a potato. A hot baked potato has a glycemic index of nearly 90. But cool it in the refrigerator for a few hours and the starch is altered to a chemical form more resistant to digestion. That lowers the potato's GI score to about 56 when you reheat it or use it in potato salad.
or re-heat it. for other meals.
Food preparation also affects a food's GI score, as does ripeness. So a soft banana has a GI score of about 80, while a firm, slightly green banana has one of about 60.
"All of these issues makes the glycemic index sound too absurd and too complex and too variable to put into practice," Brand-Miller says. "But I don't think it is as hard as people imagine."
To help guide consumers, she has teamed with Diabetes Australia and the Juvenile Diabetes Foundation to form a nonprofit group that gives foods GI numbers and labels. Under the program, foods are tested and given a score. Lean Cuisine's chicken pomodoro gets a 47, Wonder's white low-GI bread, 54; and Nestle's all-natural 99 percent fat-free mango yogurt, 55.
In the United States, it's a different story: Only one food -- a sugar substitute extracted from cactus and marketed by Sweet Cactus Farms -- has undergone testing to get the blue GI symbol. And while a growing number of weight-loss books and cookbooks pay homage to the GI approach, neither the American Diabetes Association nor many U.S. nutrition experts have embraced its widespread use.
The glycemic index is "very useful in research," says Walter Willett, chairman of the Harvard School of Public Health's nutrition department, which developed the concept of the glycemic load, a companion measure based on the GI. "But I'm not in favor of putting it on food labels or of having people shop on the basis of GI numbers."