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 protein and fat. For most active people, consuming 55 percent to 65 percent carbohydrates, plus 15-20 percent protein and 20-25 fat are ideal ranges. Some individuals feel better eating a bit more protein and less fat, but sports nutritionists don’t recommend cutting corners on the carbs.
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?
Time was, in the 1970s, carbohydrates were divided into “simple” or “complex” groups. Nutritionists suggested eating mostly complex carbs, which are plentiful in whole plant foods such as produce and beans, while avoiding the simple sugars in table sugar and sweets.
Then in the early 1980s, a 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’ research intention was to discover the best foods for people with diabetes.
A carborhydrate catalog
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.
The concept caught the attention of other researchers, nutritionists and media reporters during the next decade. More than 300 foods have been cataloged on glycemic indexes.
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.
Using the index
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 blood sugar effect by combining it with low-glycemic foods. For example, Rankin said drinking a glass of non-fat 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. What’s confusing, he said, is “how to apply it” to our everyday meals and snacks.
“The glycemic index itself is an abstraction,” said Benardot, who has worked with many Olympic athletes. “The better approach is to look at the total volume of calories in your day.”
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. Each small meal should be about two to three hours apart.
This matches up best with the typical blood-glucose cycle of rise, level out and fall.
“The goal is not to eat more frequently but to reduce total caloric load at any one time,” Benardot said. “When you eat a meal or snack, blood sugar, or glucose, increases, then levels off, then decreases. You want to eat frequently enough to catch the blood sugar before it drops outside the normal range.”
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.
This hypersensitivity to insulin production upon eating is virtually constant in obese individuals. Eating foods lower on the glycemic index will help, but the wise strategy is not skipping meals or snacks. You feel less edgy or irritable, plus become stronger and leaner.
“It looks to me like Americans are eating about twice as much as optimal,” Benardot said. “You can begin to change the pattern by splitting breakfast and lunch into four smaller meals [say, at 7 a.m., 10 a.m., 12:30 p.m. and 3:30 p.m.]. If you bring a sandwich to work, eat half at lunchtime and the other half during midafternoon.”
A global view of eating
Benardot said he recently attended a meeting in Australia. At exactly 10 a.m., a school bell sounded and the conference meeting was adjourned for coffee, tea, cakes and cookies. The same bell sounded for a break at 3:30 in the afternoon. Lectures were suspended to stay faithful to eating something every three hours.
As for dinner, Benardot said, we need look no further than Paris cafes, where portions are much smaller than the typical American nighttime meal.
“France has the lowest obesity and overweight rate among industrialized countries at 7 percent [the U.S., by comparison, is 55 percent],” said Benardot. “But no one can convince them they are eating all foods low on the glycemic index or low in fat.”
The glycemic value of some food items
The glycemic index serves as a guide to how rapidly carbohydrate foods increase your blood sugar. Foods lower on the index will release glucose more evenly into your bloodstream. Consuming food items high on the index can make you feel a bit edgy or irritable if you don’t combine them with foods lower on the index (or foods with significant protein or fat that naturally take longer to digest).
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.
The index has some surprises in its values, such as similar values for both white and whole wheat breads. But that doesn’t mean the two slices are interchangeable. Whole-wheat bread has more fiber, which helps protect against heart disease and cancer while promoting digestive well-being.
In fact, the value for whole-wheat bread is similar to orange soda pop.
Values also can vary among the same foods. For instance, long-grain rice is lower on the index than short-grain rice, and brown rice is lower than white rice. Though Idaho potatoes (best for baking) are sky-high on the glycemic index, new potatoes (low starch because they are picked before they mature) are low glycemic.
Be careful about processed foods–even soy milks–they contain too many sugars. Those sugars (listed on nutrition labels; compare carbohydrates and sugars) can significantly boost the glycemic value.
Here are some sample glycemic values, using glucose as the 100-point comparison value. (For one of the most complete listings, check out www.mendosa.com/gilists.htm.)
— B.C.
Breakfast
Cornflakes 83
Rice Krispies 82
Doughnuts 76
Waffles 76
Total 76
Cheerios 74
Bagel 72
Shredded Wheat 69
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
