What is the Glycemic Index?

THE GLYCEMIC INDEX

    Not all carbohydrates raise blood glucose equally. Brown rice may make your levels spike, while milk chocolate containing the same number of carbohydrates may raise it much less. This can be explained by the glycemic index (GI), which ranks foods based on how much they may raise glucose levels. And some people, whether they follow a lower- or higher-carb diet, pay attention to their foods’ GI, too. So, should you?
Here’s one thing experts in both the lower- and higher-carb diet camps agree on: The answer is no.

As you can see from the example above, low-GI foods aren’t always the smartest choice. (Hint: Brown rice is more nutritious than chocolate.) Many healthy foods actually have what the diet calls a medium or high GI. But that doesn’t mean you should swear off fruits and grains.

According to low-carb proponent Richard Bernstein, MD, FACE, FACN, too many factors affect a food’s GI to make the diet worthwhile. Take, for instance, an apple. Its glycemic index differs based on variety, how long it remained on the tree, how long it sat in the bin in the orchard and again in the store, and so on. Trying to calculate GI based on those details is nearly impossible.

William Yancy, Jr., MD, MHS, a researcher at the Center for Health Services Research in Primary Care at Durham (N.C.) VA Medical Center and associate professor of medicine at Duke University Medical Center, conducted a study that compared a low-carb diet and a low-GI diet. He found that the low-carb way of eating better improved blood glucose control.
“When low-GI diets are compared to high-GI diets, some short-term studies showed benefit and some did not. However, two one-year studies reported no benefit in A1C from the low-GI diets in the end,” says Marion J. Franz, MS, RD, CDE, a dietitian in Minneapolis. One study of people with type 2 diabetes found virtually no distinction between a low-GI and high-GI diet when it came to weight loss and glucose control.