The Glycemic Index and The Glycemic Load The glycemic index (GI) is a numerical system of measuring how rapidly a particular carbohydrate gets broken down into sugar and absorbed into the blood stream. This process causes varying elevations in blood sugar levels. If blood sugar levels rise to rapidly then the master hormone insulin is released. So, a low GI food will cause a small rise, while a high GI food will trigger a dramatic spike. A list of carbohydrates with their glycemic values is shown below. A GI of 70 or more is high, a GI of 56 to 69 inclusive is medium, and a GI of 55 or less is low. The glycemic load (GL) is a relatively new way to assess the impact of carbohydrate consumption that takes the glycemic index into account, but gives a fuller picture than does glycemic index alone. A GI value tells you only how quickly a particular carbohydrate turns into sugar. It doesn't tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food's effect on blood sugar. That is where glycemic load comes in. The carbohydrate in watermelon, for example, has a high GI. But there isn't a lot of it, so watermelon's glycemic load is relatively low. A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low. Quick reference guide
Rule of thumb Foods that have a low GI almost always have a low GL. Foods with an intermediate or high GI may range from very low to very high GL. Calculating Glycemic Load You will need the following information 1. Food A’s glycemic index value 2. Carbohydrate content of Food A (on food label under the “Serve Size “ column- minus the fibre from the carbohydrate content) in grams. The calculation is as follows 1/100*2=
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Take wholemeal bread for example. It has a GI index value of around 69 (depending on brand) and has approx 15 grams of carbohydrate for two slices. 69/100 = .69 * 15 = 10.35, rounded down = 10. Therefore its role in elevating blood sugar levels is relatively low, especially if combined with a good combination of protein, fat and fibre. There are plenty of web site that can help you understand the GI and GL values of foods, below I have given you but a few. I will also send you an excel sheet with the calculations on how to work out glycemic loads. Rule of Thumb For most foods and portion sizes common sense usually prevails when considering how it affects our insulin. For the foods you like but are unsure of‌check, you might be surprised‌ Please note that I will be expanding and updating this article in the next couple of months.
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