What is the glycemic index?

The glycemic index was proposed by Dr. David Jenkins at the University of Toronto in 1981 as a way of classifying carbohydrates. Very simply, it gives a score as to how quickly and how severely a carbohydrate will raise your blood sugar. It all starts by feeding a group of subjects 50 grams of glucose (which is pure sugar) and measuring their blood sugar response. This is the baseline or reference measure. Next, the researchers feed the same people 50 grams of another type of carbohydrate, say a baked potato, and measure their blood sugar response once again. 

The glycemic index number is the blood sugar response of that particular carbohydrate relative to the pure glucose reading. For example, the glycemic index of a white baked potato is 78. What that really means is when you eat equal amounts of a white baked potato and pure glucose, the potato results in 78% of the blood sugar response of the pure glucose. This test is repeated for all types of carbohydrate containing foods. A glycemic index of less than 55 is considered low.

Examples of high glycemic index foods: white bread, white rice, rice cakes, crackers, bagels, white potatoes and high sugar foods like cookies, cakes and donuts.

Examples of low glycemic index foods: fruits, vegetables, beans and minimally processed whole grains. 

Eating a lot of high glycemic index foods has been associated with risk of weight gain, type 2 diabetes, heart disease and certain cancers. Therefore, it is a really good idea to strictly limit high glycemic index foods and focus on lower glycemic carbs.