There are many things that can influence the glycaemic response, and the quantity of ingested carbohydrates, is one of them. Given that the glycaemic index is only calculated for the intake of 50 g of carbohydrates of a specific food, if the quantities of ingested carbohydrates change, the concentration of glucose in blood can vary significantly. To solve this problem, in 1997 the concept of glycaemic load (GL) was defined. This concept calculates the amount of carbohydrates in a normal serving of food and the glycaemic response it will produce.
How to calculate GL
The glycaemic load is calculated by multiplying the glycaemic index by the amount of carbohydrates (in grams) in a serving of food and dividing the result by 100. This way, we obtain a number that is closer to the way a certain serving of food will influence our blood-sugar levels.
Let’s see an example:
Pasta can be cooked in many ways, there are those who like it al dente, with oil, with vegetables, filled with meat… all these different cooking techniques will affect the glycaemic index in a recipe. The glycaemic load takes them into account.
1 serving of pasta = 80 g when raw (54 g of carbohydrates)
GI of white al dente spaghetti = 46
GI of white spaghetti cooked for 10-15 min = 58
The GL of white al dente spaghetti = (46 x 54) / 100 = 25
The GL of white spaghetti cooked for 10-15min = (58 x 54) / 100 = 31
If we combine the al dente pasta with fresh spinach leaves and tomato, we lower the GL because the cooking of the pasta is quick and it gets mixed with foods that are rich in fibre. The serving sizes will also be important in order to control blood-sugar levels.
GL classification
- High GL: equal to or higher than 20 (≥ 20)
- Medium GL: between 11 and 19
- Low GL: equal to or lower than 10 (≤10)
REMEMBER: A certain food can have a very high GI and still present a low GL, because the quantity of the product that is ingested in a serving can be small and not have a big impact on blood-sugar levels. The opposite can also happen.