Glycemic index and blood glucose

Controlling blood glucose using glycemic index.

Glycemic index (GI) is a ranking system that indicates how quickly a carbohydrate food raises blood glucose levels in the body. It compares the response that your body has after eating food to a standard amount of glucose. It is determined by measuring two hours after the test food is consumed and then compared to a similar weight of glucose or bread. Foods are then assigned a number value which is put into a range of low, moderate and high ranking. Foods ranked less than 55 are considered to have low GI, whereas foods measuring 56 through 75 have a moderate GI. Highly processed and refined carbohydrates, such as white bread, rank 76 through 100 on the GI scale.

Another measure called the glycemic load (GL) reflects the usual amounts of carbohydrate portions. This is calculated based on the GI and the portion size of the food eaten. As with the GI, the GL also has a scale of low and high. GL values less than 10 are considered low and greater than 20 are considered high. Glycemic Load indicates the overall impact of the carbohydrate on the body based on the portion size eaten.

Aiming for both the type and the amount of carbohydrates consumed is a key to optimal blood glucose control, keeping in mind that not all carbohydrates are created equal. Research shows that using the GI and meal planning can improve diabetes control slightly, but can be complicated. Michigan State University Extension says that the following factors affect the GI in foods:

  • The more processed the food, the higher the GI
  • Ripeness; the more ripe a food is, the higher the GI
  • Complement a high-GI food with a low-GI food. When carbohydrate foods are eaten as part of a meal, the average of the GI values is factored together.
  • Cooking time; longer cooking times may break down the starch more and allowing it to pass through the body faster.
  • Food acidity; the more acidic a food, the lower the GI.
  • Physical barrier; plant cell walls slow the digestive process, slowing carbohydrate breakdown.
  • Protein/fat-adding protein or fat to a high GI food decreases the GI of that food.
  • Soluble fiber-the higher the food is in soluble fiber, the lower the GI.

There is increasing evidence that choosing foods with low GI and GL shows a positive effect on blood glucose. It is very important to see your physician and/or diabetes educator to receive proper counseling to reach an optimal blood glucose level that works for you in the short term and long term.

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