Written by Anssi Manninen, MHS
13 March 2007

The glycemic index (GI) is a ranking of carbs on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those that are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Examples of such foods include white bread, potatoes and sugar-loaded snacks. In contrast, low-GI foods, by virtue of their slower digestion and absorption, produce gradual rises in blood sugar and insulin levels. In general, vegetables and legumes have a very low GI. Although there’s evidence that high-GI foods increase the risk of diabetes, obesity and heart disease, traditional nutritionists have pretty much dismissed the whole GI concept. They maintain that the glycemic index doesn’t apply in mixed meals and thus has no practical value. This isn’t the case, however. A recent literature review by Dr. Thomas Wolever (Department of Nutritional Sciences, University of Toronto) discussed common misconceptions about the GI. As pointed out by Wolver, the notion that the glycemic index doesn’t apply in mixed meals is based on flawed methodology. Recent studies show that nearly 90 percent of the variation in glycemic response of realistic mixed meals can be explained by differences in carb content and GI. In other words, the GI concept is real. Stick with the lower GI foods. However, don't become too obsessed. For example, you shouldn’t avoid cooked carrots because of their high GI, so use common sense too!

 

Reference: Wolever TM, Physiological mechanisms and observed health impacts related to the glycemic index: some observations. Int J Obes (Lond), 2006 Dec;30 Suppl 3:S72-8.