The Glycemic Index is limited tool for managing diabetes.
Some carbohydrates are absorbed or metabolized quickly, causing blood sugar to spike, while others are absorbed more slowly, making it easier to keep blood sugar even.
One guide for evaluating carbohydrates is called the glycemic index. It’s a way of comparing how the carbohydrates in different foods raise blood sugar.
But relying solely on the glycemic index to plan your diet isn’t as straightforward as popular diets and weight loss marketing campaigns may make it sound.
"It isn't that simple,” said Barbara V. Howard, Ph.d, senior scientist at MedStarHealth Research Institute and professor of medicine at Georgetown University School of Medicine. “ Just knowing the glycemic index value is an over simplification.”
Making Sense of the Glycemic Index
While it’s possible to look up the glycemic index for individual foods, “most people never only eat one food at a time,” said Dr. Howard, who is also an AHA volunteer.
“A potato may have a high glycemic index if it’s a baked potato, but a much lower one if it’s in a casserole with green beans, meat or other food,” Dr. Howard said.
How food is cooked can also change the way your body processes the carbohydrates.
“It’s very clear that if a certain amount of fat is ingested , it will retard the absorption of sugar no matter what the glycemic index is,” Dr. Howard said.
Food that gets processed in different ways may not have the same glycemic values. For example, oatmeal made using rolled, or steel-cut oats has a low glycemic index, but the cereal using “instant” oats has a high glycemic index.
Dr. Howard said the glycemic index is most useful as a tool for snacks, when foods are less likely to be combined.
Eat a Balanced Diet
The AHA encourages patients with diabetes to use glycemic index as one consideration in choosing the healthiest carbohydrates, but not the only method for planning your diet.
Complex carbohydrates, such as whole grains, are generally more healthful, but that’s because of the nutrients in those foods, not the glycemic index, Dr. Howard said.
And just because a food has a high glycemic index doesn’t meant it’s not good for you.
“Fruits tend to have higher glycemic indices, but they’re also good for you and a great to eat for a snack,” Dr. Howard said.
And don’t forget: Watch your portions, Dr. Howard warned. “Just because something is high glycemic, doesn’t mean you can eat as much of it as you want.”