Studies show when considering the effect of carbohydrates on blood glucose, it is not just how many carbohydrates you eat but their source as well.1 Some foods cause a quick rise in blood glucose after a meal, while others cause a smaller peak and more gradual decline in blood glucose levels. The measure of how fast a food causes blood glucose to peak is called its glycemic index, or GI.
What a Glycemic Index (GI) Number Means
High-carbohydrate foods are ranked on a scale of 1 to 100, with 100 representing the effect of pure glucose on the body. The lower the GI of a food, the slower its peak. The way the food is cooked (for example, frying vs. baking) can also determine the GI level of the food. The GI breaks foods into 3 levels:2,3
- Low: less than 55
- Intermediate: between 55 and 70
- High: above 70
A few low-GI foods include:
- Whole-grain breads and cereals
- Brown rice
- Dried beans and lentils
- Old-fashioned oatmeal
- Sweet potatoes
- Dairy products
- Apples and oranges
Meats and fats are low in carbohydrates and do not have a GI ranking.
Used in combination with carbohydrate counting, looking at food GI levels may help you stabilize your blood glucose throughout the day. The rule of thumb is that the higher the GI, the smaller the portion you should have. Conversely, you can eat more of lower-GI foods without overloading your blood glucose.
You can choose foods from the low-GI category more often and see if it helps you maintain closer-to-normal blood glucose levels.
1Archives of Internal Medicine 2006;166:1466-1475 'Comparison of 4 diets of varying glycemic load on weight loss and cardiovascular risk reduction in overweight and obese young adults: a randomised controlled trial.' Available at http://archinte.ama-assn.org/cgi/content/short/166/14/1466. Accessed on November 17, 2008.
2International Diabetes Institute. Glycemic Index. Available at http://www.diabetes.com.au/about.php?regionID=254. Accessed on November 17, 2008.
3Canadian Diabetes Association Glycemic Index