Researchers continue studies on usefulness of glycemic index in diet

If you pick up a box of Lean Cuisine Chicken Pomodoro in Australia, 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. About 150 other products carry the symbol, too.

Developed nearly 30 years ago at the University of Toronto, the glycemic index, or GI, is becoming part of the nutritional landscape Down Under. And it has attracted attention here and in Canada, too, among nutrition researchers and writers 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 the number, the more likely your blood sugar will be elevated after eating — something people, especially those with diabetes, need to avoid. Foods with scores 70 to 100 are considered high glycemic; 55 and lower are low glycemic.

In recent years, the glycemic index has been popularized by Jennie Brand-Miller, professor of nutrition at the University of Sydney and author of “The New Glucose Revolution” and 15 other books that have sold more than 3 million copies.

Many people think that eating according to the glycemic index simply means skipping 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 score to about 56, taking it from a high glycemic food to much lower one.

While preparation can affect a food’s glycemic index score, so does ripeness: A soft banana has a GI of about 80, while a firm, slightly green banana has one of about 60.

“All of these issues make the glycemic index sound too absurd and too complex and too variable to put into practice,” notes Brand-Miller. “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 Research Foundation to form a nonprofit group that gives foods glycemic index numbers and labels. Under this program, foods are tested three times and given a score. Chicken Pomodoro gets a 47, Wonder White Low GI Bread, 54; Nestle All-Natural 99 Percent Fat-Free Mango yogurt, 55; and Bulla 98 Percent Fat-Free Vanilla Ice Cream, 36.

In the United States, it’s a different story: Only one food — a naturally occurring sugar substitute extracted from cactus and marketed by Sweet Cactus Farms — has undergone testing to earn the GI symbol. And while a growing number of weight-loss books and cookbooks pay homage to the glycemic index 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,” notes Walter Willett, chair of the Harvard School of Public Health’s nutrition department. “It’s useful for consumers to have a conceptual idea of the glycemic index, but I’m not in favor of putting it on food labels or of having people shop on the basis of GI numbers.”

Now, two new reports published in this month’s American Journal of Clinical Nutrition — and two editorials commenting on the findings — probably will add to the debate. Neither found benefits in using the GI approach to control blood sugar or to cut the risk of heart disease and Type 2 diabetes.

The findings suggest “that there is relatively little role for the glycemic index in preventing or controlling Type 2 diabetes or in weight loss,” says David M. Nathan, director of the Massachusetts General Hospital’s Diabetes Center.

At the Mayo Clinic, endocrinologist John Miles counsels his patients with — and without — diabetes to cut calories and fat to lose weight, rather than worrying about the glycemic index.

“I see a lot of patients eating sugar-free diets, who also avoid starch, but end up on high-fat diets. This does not make sense,” he says. “I am all for eating whole-grain bread, but if we allow our patients to put butter or a slice of cheddar cheese on it, they’d be better off eating Wonder Bread (with a relatively high GI).”

So where does this leave you while scientists sort it all out? Whether you count the GI numbers or not, everyone agrees you can’t go wrong by eating plenty of fruits and vegetables, some whole grains and a few healthy fats.

Join Sally Squires online from 10 to 11 a.m. Tuesdays at www.leanplateclub.com, where you also can subscribe to the free Lean Plate Club weekly e-mail newsletter.

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