Understanding the Glycemic Index

Understanding The Glycemic Index

Are you left feeling hungry soon after finishing a meal? Are you frustrated with high blood glucose numbers hours after a meal? If you answered “yes” to either question, read on to learn more about how using the glycemic index and glycemic load may help.

Many people with diabetes count carbohydrates at meals as a way to control blood sugar numbers, however, certain carbohydrates seem to have more impact on blood sugar numbers than other carbohydrate foods. This is when understanding the glycemic index and glycemic load can be helpful.

The glycemic index is a ranking system of how quickly a carbohydrate food raises the blood glucose level. Foods are ranked on a scale of 0 to 100. The higher the number, the greater the blood glucose response will be. The glycemic index of a food is determined by plotting blood glucose levels for two hours after subjects eat a food containing 50 grams of carbohydrate, which is then compared to a reference food such as pure glucose.

The usefulness of the glycemic index in managing blood glucose levels has been debated. Additional research suggests that the glycemic load of a food may be more useful in management of blood glucose levels. The glycemic impact (also known as the glycemic load) takes into consideration both the glycemic index of a food as well as the grams of carbohydrate in one serving. Glycemic load = glycemic index x grams of carbohydrate per serving.

Ranking Scale for Glycemic Index and Glycemic Load:

Glycemic Index ScaleGlycemic Load Scale
Low< 55Low<10

What are some of the potential health benefits of following a low glycemic index diet?

  • Less glycemic variability (which has been shown to reduce the risk of microvascular complications)
  • Improved insulin sensitivity
  • Improved glycemic control (The Standards of Medical Care in Diabetes from 2014 reported: Substituting low-glycemic load foods for higher-glycemic load foods may modestly improve glycemic control)
  • Raise HDL (good cholesterol)
  • May facilitate weight loss by increasing feeling of fullness after a meal

What factors affect the glycemic index?

  • Fiber: higher fiber typically will be lower in the glycemic index
  • Cook time: longer cook times increase the glycemic index
  • Processing: in general the more processed a food is, the higher the glycemic index will be
  • Acidity: the more acidic a food is, the lower it will be in the glycemic index
  • Protein and fat: both nutrients slow down the absorption of carbohydrates thereby lowering the glycemic impact
  • Ripeness: the more ripe a fruit, the higher the glycemic index

How do some common foods rank?

  • Low glycemic impact:
    • Sourdough bread, All-Bran cereal, steel cut oats/oatmeal, milk, yogurt, lentils, dried beans, strawberries, blueberries, apples
  • Moderate glycemic impact:
    • Whole wheat bread, Raisin Bran, tortillas, pasta, bananas, sweet potato, corn
  • High glycemic impact
    • Bagel, white bread, Cornflakes, instant oatmeal, instant rice, potato, soft drinks

A weeks worth of tips:

Monday: Avoid “instant” products. Instead of having an instant oatmeal packet for breakfast try making steel cut oats. Add some cinnamon and fresh berries for a little extra flavor.

Tuesday: Improve your afternoon snack. Try an apple with peanut butter.

Wednesday: Think whole grain. Swap out white pasta for whole-wheat pasta.

Thursday: Hot potato. Try a baked sweet potato instead of a white potato with your dinner meal.

Friday: Choose unprocessed foods. Processed foods are more commonly found in the aisles of the grocery store and typically do not require refrigeration.

Saturday: Try a new cereal. Replace Cornflakes with All-Bran cereal.

Sunday: Don’t overcook your food. Boil pasta until it is al-dente.

How will I know this is making a difference?

Check your blood glucose 1.5 to 2 hours after eating a lower glycemic index meal. The American Diabetes Association recommends blood glucose readings be < 180 mg/dL 1.5 to 2 hours after the start of a meal.

Check in with yourself! Did your meal keep you satisfied longer?

Bottom Line:

Look at the big picture. Choose foods that are fresh and unprocessed as much as you can and remember: just because a food is ranked as “low” on the glycemic index scale does not mean it is always the healthier choice. Choosing foods that are lower on the glycemic index, in addition to counting carbohydrates at meals, may be the extra step that helps you reach your glycemic goals!

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