Glycemic Load Vs. Glycemic Index

"The Glycemic Index of a food is a numerical unit describing how far eating a food will raise one’s blood sugar level; effectively, it represents how ‘sugary’ the food is. The Glycemic Index uses a scale from 0 to 100, where 100 is pure glucose. A food which has a high GI will cause a large increase in blood sugar, while a food with a lower GI will not have much impact at all. As a rough basis, mid-50s to mid-60s in a food’s GI is considered average, while 70 and above is considered high. Foods with a GI of less than 55 are considered to have a low glycemic index, and thus will have smaller impact on blood sugar levels.

The main problem with the Glycemic Index is that it does not factor in typical portion sizes. In fact, it standardizes each food to include 50 grams of carbohydrates. This leads to some peculiar distortions. For example, to obtain 50 grams of carbohydrates you would need either 2.8 ounces of a Snickers bar or 35 ounces of pumpkin. It hardly seems fair to compare the two when these portion sizes are so unrealistic!

In 1997, researchers at Harvard University introduced the concept of Glycemic Load with the aim of solving this problem. The Glycemic Load seeks to balance the Glycemic Index by accounting for serving size. Let’s take a watermelon as an example. It has a high GI, as the carbohydrate will increase blood sugar levels rapidly, but it contains a relatively small amount of the carbohydrate, meaning that it has a low glycemic load.

A food’s Glycemic Load is calculated directly from its Glycemic Index. We simply take the food’s Glycemic Index, divide it by 100, and multiply it by the grams of carbohydrate (excluding fiber) in a typical serving size. A GL of above 20 is considered high, the 11-19 range is considered average, and below 11 is low.

Let’s look again at watermelon. It has a Glycemic Index of 72, which is relatively high. However, a typical serving size only has 5 grams of carbohydrate. This means we can calculate the Glycemic Load like this: 72/100*5 = 3.6. Although the Glycemic Index is high, the Glycemic Load is relatively low. Which one is more useful to us? The Glycemic Load."

To find out which fruits have the lowest glycemic load, continue reading the above article here