Is the Glycemic Index Helpful for People with Diabetes?

Woman with diabetes
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The glycemic index may be helpful for diabetics, or maybe not. Research studies on using the glycemic index as a basis of a diabetic diet have produced mixed results. Probably because there are two different versions of the index, and neither takes serving or portion size into consideration. Another value called the glycemic load may be more helpful, but counting carbohydrates or following a consistent carbohydrate diet are still the best ways to build a diabetic diet.

Glycemic Index

The glycemic index is a method of measuring how high-carbohydrate-containing foods raise blood sugar (glucose) levels after you eat them, using a scale from one to 100. Foods near the top of the index increase blood glucose levels higher than foods closer to the bottom. One glycemic index uses white bread as the standard reference of 100, but another index uses glucose. So you need to know which index you're using -- it's easy to get confused.

Planning a diet based on the glycemic index involves choosing foods that have low to medium index numbers. Low glycemic index foods include legumes, non-starchy vegetables, whole grains and some fruits. Meat, poultry, fish and eggs don't have any carbohydrates, so they're essentially given zeros for calculating indexes. Cooking methods, cooking time, and degree of ripeness can affect the glycemic index of foods, and different brands of the same food can have different values.

For example, mashed potatoes have a higher index number than a baked potato, and both can change depending on what you put on top. Different brands of whole wheat bread can vary as much as 20 points on the index

The glycemic index seems like a good idea, and it can help you get tuned into which foods are higher in carbs than others.

But it doesn't take portion size, calorie counts or nutritional value into consideration, so it isn't sufficient for planning your diet. For example, watermelon has higher index number than ice cream, and potato chips have a lower value than a baked potato. That's because they also contain fat, which lowers the glycemic index number but doesn't make them more nutritious.

Glycemic Load

Since the glycemic index can be a bit awkward to use, something called the glycemic load can be calculated. It's based on the glycemic index but also uses standardized portion sizes so that it's more useful. The formula used for calculating the load is the glycemic index times the amount of carbohydrate, divided by 100. Low glycemic load foods are under 10, medium ranges from 11 - 19 and foods with a score of twenty or more are considered high-glycemic-load foods. If you have diabetes, make sure you speak with your health care provider, diabetes educator, dietitian or nutritionist before making any dietary changes.

Sources:

American Diabetes Association. "Glycemic Index and Diabetes." Accessed April 14, 2016. http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/understanding-carbohydrates/glycemic-index-and-diabetes.html .

Academy of Nutrition and Dietetics Evidence Analysis Library. "Recommendations Summary Diabetes Mellitus (DM): Glycemic Index and Diabetes" Accessed April 14, 2016. http://www.andeal.org/.

Maher AK. "Simplified Diet Menu." Eleventh Edition, Hoboken NJ, USA: Wiley-Blackwell Publishing, October 2011. Accessed April 14, 2016.

Harvard Health Publications, Harvard Medical School. "Glycemic Index and Glycemic Load for 100+ Foods" Accessed April 14, 2016. http://www.health.harvard.edu/diseases-and-conditions/glycemic_index_and_glycemic_load_for_100_foods.

University of Illinois Extension. "What is the Glycemic Load and Glycemic Index? Accessed April 14, 2016. http://extension.illinois.edu/diabetes2/subsection.cfm?SubSectionID=100.

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