Nutrition News: Glycemic Index
Should you care about a food's glycemic index?
Maybe, maybe not.
The glycemic index, simply put, is a measure of how quickly a food causes blood sugar levels to rise.
The measure ranks food on a scale of 0 to 100. Foods with a high glycemic index, or GI, are quickly digested and absorbed, causing a rapid rise in blood sugar. The foods that rank high on the GI scale are often -- but not always -- high in processed carbohydrates and sugars. Pretzels, for example, have a glycemic index of 83; and a baked potato without the skin clocks in at 98, according to the Academy of Nutrition and Dietetics.
Meanwhile, foods with a low GI are digested and absorbed at a slower rate, and, subsequently, cause a slower rise in blood sugar levels. These are typically rich in fiber, protein and/or fat. Examples of these include apples with a glycemic index of 28, Greek-style yogurt at 11, and peanuts at 7. However, keep in mind that a low GI doesn't mean a food is high in nutrients. You still need to choose healthy foods from all five food groups.
Diets centered on mostly low-GI foods can make it easier to achieve and maintain a healthy weight, since these foods keep us feeling fuller, longer. Low-GI diets also have been shown to improve insulin resistance, and lower glucose, cholesterol and triglyceride levels in people with type 2 diabetes.
One exception to the recommendation of a mostly low-GI diet is after intense or prolonged exercise. Consuming high glycemic foods can actually be more beneficial for muscle recovery, since they're rapidly digested.
But there's a problem putting too much stock in the GI -- A food's GI ranking only applies when a food is consumed on an empty stomach without any other type of food. That isn't always how we eat. We may have a bag of pretzels as a stand-alone snack, but we typically don't eat just a plain potato with nothing else. If we add a lean steak or a piece of salmon, a side of broccoli and a salad with vinaigrette, and the protein, fiber and fat all serve to lower the glycemic index of the meal.
In addition, the glycemic index doesn't take into account how much food is actually consumed. The GI value of a food is determined by giving people a serving of the food that contains 50 grams of carbohydrate minus the fiber, then measuring the effect on their blood glucose levels over the next two hours.