A Perfect Score
Use the glycemic index to convert carbohydrates into healthful eating
By Chris O'Brien
The glycemic index—a glycemic rating of hundreds of foods, long used by diabetics to help control blood sugar levels—is a great way to monitor carbohydrates and their effect on your body. In a nutshell, the index assigns ratings to different products, telling how fast vegetables, grains, or other foods will convert to blood sugar. According to Jennie Brand-Miller, PhD, co-author of The Glucose Revolution: The Authoritative Guide to the Glycemic Index (Marlowe & Co., 1999), eating foods that score low on the index is a key to better health, including lowering your risk for diabetes and heart disease, controlling weight, and even improving athletic performance.
Sound like a new wonder cure? Not exactly. The benefits of this scoring system are simply a recent interpretation of information that's been around for a while. "The glycemic index is not a new concept," says Ann Louise Gittleman, MS, CNS, author of The Fat Flush Plan (McGraw-Hill, 2001). "It was created years ago, but it has only recently gained notoriety in the wake of low-carb diets." Developed in 1981 by David Jenkins, PhD, professor of nutrition at the University of Toronto, the index quantified food-conversion rates, which Jenkins proposed might help diabetics manage their diet.
Reading The Index
Here's how the glycemic index works: Each food's assigned number indicates how fast that food converts to sugar in the body, how high the blood sugar level is raised, and how long it stays elevated. The most common indexes measure the increase in blood sugar level over a fixed time period—usually two hours—after eating a certain food, compared with the average increase after eating 50 grams of white bread. (Because white bread raises blood sugar similarly to pure glucose, it is the standard baseline food.) For example, eating a mango (80 glycemic index rating) will raise your blood sugar 80 percent as high as 50 grams of white bread would over a two-hour period.
This knowledge puts better health in your hands because persistently high blood sugar is linked to myriad health problems, including heart disease, diabetes, and free radical stress from the oxidation of glucose. In fact, glucose oxidizes much more readily than fats, leading some experts to believe that too much sugar is more damaging to the body than too much fat.
Why Go Low
The bottom line? A low-glycemic diet may benefit your body—and it's not just for diabetics. While researchers who studied Type II diabetics found that a low-glycemic diet lowered blood sugar levels, enhanced insulin response, improved cholesterol levels, and benefited vascular health (Diabetes Care, 1999, vol. 22, no. 1), researchers of another study of nondiabetics found that eating a low-to-moderate index-based meal 45 minutes before exercise provided more sustained energy and better performance than a high-scoring index meal (Metabolism, 2001, vol. 50, no. 7). In addition, low-glycemic foods may help children and adults who suffer from obesity because unused sugar in the bloodstream gets converted to fat for storage (Archives of Pediatrics & Adolescent Medicine, 2000, vol. 154, no. 9; American Journal of Clinical Nutrition, 1994, vol. 59, suppl. 3).
However, while low is good, you needn't completely avoid high-scoring items. "It's wrong to think that because one food has a high glycemic index it's bad and another with a low glycemic index is good," says Jonny Bowden, MA, CNS, author of Jonny Bowden's Shape Up! The 8-Week Plan to Transform Your Body, Your Health, and Your Life (Perseus Books Group, 2001). "Nobody ever became diabetic from eating peas or carrots, and there are plenty of junk foods with low glycemic indexes."
So don't neglect a balance of nutrients. Fats, proteins, and fiber, although exerting less effect on blood sugar than carbs, do affect how fast sugar gets absorbed into the bloodstream because their digestion slows the carbohydrate-to-sugar conversion. "Fat is the best blood sugar-stabilizing material," Gittleman says. "But it's important to eat the right kinds of fats, like avocado, olive oil, and nuts, rather than hydrogenated oils." Bowden agrees that fats and soluble fibers will decrease the glycemic index, but adds, "that doesn't mean they're always healthy—a McDonald's burger has a low glycemic index [rating]."
How to find the glycemic index
To find out more and to get complete GI tables, try these sources: The Glucose Revolution: The Authoritative Guide to the Glycemic Index
by Jennie Brand-Miller, PhD, et al. (Marlowe & Co., 1999)
Pocket guide also available.
Harvard Health Publications Web site
Rick Mendosa, diabetes specialist
www.mendosa.com/gilists.htm The basic approach: Choose high-fiber, whole foods in as natural a state as possible. Avoid processed grains such as pasta, bread, and cereal, which tend to be higher on the index and are often void of phytonutrients, fiber, vitamins, and minerals. Whole fruits and vegetables are a little higher on the index but still provide the body with essential vitamins, minerals, and antioxidants. Organic meat is another low-scoring food because it's made up primarily of protein and fat. "The whole point of the glycemic index is to give you a tool to make healthier carbohydrate substitutions in your diet," says Rick Mendosa, an Aptos, California, freelance medical writer and glycemic index and diabetes specialist. Whether you are at risk for diabetes or just trying to stay healthy and keep fit, the glycemic index can help you choose foods for better health.
Chris O'Brien is a freelance writer specializing in health, nutrition, and supplements.