How Sweet It Is: If You’re Eating Carbs, Check an Index
Everyone’s training table needs carbohydrates; there’s no argument about that. Our bodies convert carbohydrates to glycogen, which serves as our main fuel in muscles.
The hottest debate about carbs focuses on how many you need in your diet compared with amounts of protein and fat. For most active people, consuming 55% to 65% carbohydrates, plus 15% to 20% protein and 20% to 25% fat, are ideal ranges.
Nonetheless, more than a few nutritionists say Americans are missing a more fundamental question about carbohydrates: Just which ones are best for feeling good and increasing energy? In the 1970s, carbohydrates were divided into simple or complex groups. Nutritionists suggested eating mostly complex carbs, such as produce and beans, while avoiding the simple sugars in table sugar and sweets.
Then in the early 1980s, University of Toronto researcher David Jenkins discovered some complex carbohydrate foods actually rushed their way into the bloodstream. Foods such as potatoes and rice led to a fast rise in blood sugar or blood glucose, followed by the matching rapid drop in glucose levels. Jenkins’ intention was to discover the best foods for people with diabetes.
He created the glycemic index, which measures how fast carbohydrates in a certain food convert to glucose, which then enters the bloodstream and muscles (as glycogen). The glycemic index basically tracks how fast your blood sugar rises after eating carbohydrate-dense foods, such as fruits, vegetables, grains and processed foods (pasta, bread, cereals, crackers and cookies are measured most often).
In his first study, Jenkins listed values for a variety of foods. The value of glucose (a simple sugar) was 100. All other foods were matched against it and slotted as low-, medium- or high-glycemic foods. More than 300 foods have been cataloged.
Other glycemic indexes were produced, using white bread as the 100 value because it is a common food among Americans. If you are ever confused about why certain foods have different glycemic index values, that’s why. Other times you may see a food higher in one listing than another. Whether the food is cooked or raw can change values; the same goes for ripeness. An unripe banana is about 30 points lower in glycemic effect than a ripe one.
Proponents of the glycemic index recommend eating carbohydrate foods lower on this scale for optimal health. Some champions of the index, including nationally known authors, contend that using the rating system is the best way to lose weight and feel healthy. Janet Rankin, a professor in the human nutrition, foods and exercise department at Virginia Tech, isn’t that enthralled with the glycemic index.
“People tend to overuse the glycemic index,” she said. “It is more valuable at snack time, since that is when we tend to eat single food items.”
In general, Rankin said, Americans consume lots of high glycemic foods, such as white bread and bagels. Recognizing high-glycemic foods can help you make better choices. Or you can alter the food’s sugar effect by combining it with low-glycemic foods. For example, Rankin said drinking a glass of nonfat milk with your bagel “significantly lowers the glycemic value.”
Rankin said high-glycemic foods are most valuable during exercise: “Research shows these foods do their job by getting glucose into the bloodstream quickly when you need it.”
The studies are less clear about consuming high-glycemic foods after a workout, though some nutritionists suggest this is about as good a time as any to munch on a sugary treat because your body needs the carbs for recovery.
Dan Benardot, associate dean of nutrition research at Georgia State University, said the glycemic index is a clearly designed instrument but can be confusing in “how to apply it” to everyday eating.
Benardot said the single best change you can make in your daily diet is reducing the size of meals. He proposes eating six small meals rather than three larger ones. This matches up best with the typical blood-glucose cycle of rise, level out and fall.
If you eat more frequently, your body has a more controlled response to foods. Going too long between meals or snacks causes your body to pump out more insulin when you do eat, Benardot said, a condition that causes too much flux in blood glucose.
Nutritionists generally recommend eating more foods low or moderate on the index (less than 50) and selecting more healthy foods among those high on the index. Here are some sample glycemic values, using glucose as the 100-point comparison value.
Breakfast: Cornflakes, 83; Rice Krispies, 82; doughnuts, 76; waffles, 76; Total, 76; Cheerios, 74; bagel, 72; oatmeal, 49; yogurt, sweetened, 33; soy milk, 30.
Lunch: White bread, 71; whole wheat bread, 69; taco shells, 68; cheese pizza, 60; white pita bread, 57; green peas, 48; baked beans, 43.
Dinner: Instant rice, 91; white rice, 88 (some versions as low as 55); baked potato, 83; spaghetti, 40; black beans, 30.
Snacks: Vanilla wafers, 77; orange soda, 68; angel food cake, 67; raisins, 64; ice cream, 61; grapes, 52; orange, 43; Snickers bar, 41; apple, 38.
For one of the more complete listings, check out www.mendosa.com/gilists.htm.
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Bob Condor is a reporter for the Chicago Tribune, a Tribune company.
