Should Diabetics Use the Glycemic Index?

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U.S. News & World Report
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How the GI can help you with carb-containing foods, plus a look at its limitations.

By Vanessa Caceres

If you have diabetes, you may have heard about something called the glycemic index and wonder if it can help you manage your blood sugar.

The glycemic index is a number between 0 and 100 given to a food with carbohydrates to determine how fast it will raise your blood sugar level once you eat it. The higher the number, the more likely that food is to raise your blood sugar quickly.

“We like to steer patients, especially those with diabetes, away from foods high on the glycemic index,” says Dr. Rahil Bandukwala, an endocrinologist at Saddleback Medical Center in Laguna Hills, California. That way, you can help avoid the complications associated with high blood sugar levels.

Some examples of foods considered low on the glycemic index (55 or less) include sweet potatoes, rolled or steel-cut oatmeal and most fruits and nonstarchy vegetables, according to the American Diabetes Association. Medium-ranked foods (56 to 69) include brown rice and certain kinds of whole wheat bread. Foods high on the glycemic index include white bread, instant oatmeal and, perhaps surprisingly, melons and pineapple.

Although melons and pineapple are high on the glycemic index because of their high content of natural sugar, they also contain fiber, which makes them healthier choices than, say, a piece of white bread.

One downside of the glycemic index is that it doesn’t assign a number to food combinations, Bandukwala says. When you eat a food high on the glycemic index, the American Diabetes Association says you can combine it with other low glycemic index foods to balance out the effect on blood glucose levels. For example, a cookie may be high on the glycemic index, but combining it with a glass of milk (which ranks only 31 on the index) helps to lower that effect – not that you want to spend too much time eating cookies.

Several things can affect where a food ranks on the glycemic index, including how ripe a fruit or vegetable is (when it’s more ripe, it has a higher number), processing (more processed foods usually have higher numbers), variety and cooking method. “For example, pasta cooked for 20 minutes will have a higher glycemic index of 58 than pasta cooked al dente,” says registered dietitian and certified diabetes educator Lorena Drago, a senior associate director of Ambulatory Care Nutrition Programs at Lincoln Hospital in Bronx, New York, and owner of Hispanic Foodways. Pasta that is al dente – not overcooked – is just 46.

There’s also a concept called the glycemic load. “The glycemic load is a ranking system that measures how much a food will raise blood glucose levels based on the food’s glycemic index and the amount of food eaten,” Drago says. “A glycemic load under 10 is considered low, 11 to 19 is considered medium and 20 and higher is considered high.”

The glycemic load can more accurately show a food’s impact on your blood sugar, according to a website from Harvard Medical School in Boston. To find out a food’s glycemic load, you multiply the grams of carbohydrate in a food serving by the food’s glycemic index, and then divide that total by 100. Or, you can use the various charts available online that have already done the math for you, like the one on the Harvard Medical School site that demontrates glycemic index and load numbers for 100 foods.

Remember that earlier example with melon? Watermelon has a glycemic index of 80 but it only has six grams of carbohydrates. So, its glycemic load is only 5, which is considered low.

Another example is the popular snack of microwave popcorn. A plain serving is high at 65 on the index. But its glycemic load is low, at only 7. That’s in contrast to cornflakes, which are actually high both on the glycemic index (81) and glycemic load (20).

Unsweetened orange juice, which is often recommended when someone has low blood sugar, is 50 on the glycemic index but only 12 on the glycemic load. That’s lower than a number of other juices and soda.

When you have diabetes, you usually have a lot on your mind regarding your diabetes care. So are the glycemic index and glycemic load concepts you should be using?

It depends.

On one hand, Sandra Arévalo, a registered dietitian and certified diabetes educator and director of nutrition services for Montefiore Health System’s Community Programs in Bronx, New York, does not discuss it with her patients.

“People with diabetes have so many things to worry about. This puts another burden on them,” says Arévalo, who is also a U.S. News contributor. That burden includes carrying around and possibly memorizing the glycemic index and glycemic load numbers for certain foods.

“It can get very complicated to translate the glycemic index into practice,” Bandukwala says. He brings it up if patients seem to desire more detailed dietary information, and he finds that patients with Type 1 diabetes usually get the concept quicker because they’ve seen firsthand how their blood sugar can rapidly change by eating certain foods. “For Type 2 patients on two or three oral medications, it can be hard to conceptualize,” he says.

On the other hand, “studies have shown that choosing low glycemic index/glycemic load foods confer an additional benefit to managing blood glucose,” Drago says.

Glycemic index/load numbers can be an additional tool in helping you to identify quality carbohydrates. However, if it’s not a concept that you plan to use, then continue to focus on eating healthy carbohydrates with balanced meals that include protein, healthy fats and fiber. One example of such a meal that Arévalo shares is half a plate full of green leafy or vibrant-colored vegetables, one-fourth a plate of lean protein like chicken, fish or turkey; and one-fourth a plate of healthy carbs such as brown rice, garbanzo beans or quinoa.

If you’ve eaten a meal with foods that may be high on the glycemic index/glycemic load, don’t worry. “One meal is seldom going to have a deleterious effect on diabetes management,” Drago says. “However, it is important to best blood glucose levels one to two hours after a meal.” If you use fast-acting insulin, adjust your dosing as needed.