El índice glucémico


You’ve probably heard of the glycemic index (GI), but do you know what it is? This is a system for quantifying the glycemic response of a food. That is, measuring how quickly carbohydrates from a portion of food pass into the blood as glucose after eating. The faster this process, the more prominent the blood sugar spike.

The glycemic index of all foods is not usually measured. Typically, only those considered to contain a minimum amount of carbohydrates are taken into account and not all of them work in the same way in our organism. Some have a very high glycemic index, causing a rapid rise in blood sugar, while others act more slowly and prevent high and rapid increases in blood sugar.  


The glycemic index is sometimes confused with the glycemic load, and no, they are not the same thing, although they are related. When we speak of the glycemic index we are indicating the speed with which edible portions pass into the blood, that is, the speed with which a food raises blood glucose after ingestion. By glycemic load, on the other hand, we refer to the total amount of carbohydrates contained in a serving.


The glycemic index scale ranges from 0 to 100. Therefore, we will say that pure glucose has the highest glycemic index and that it is equivalent to a value of 100:

>70 high glycemic index
55-69 medium or low glycemic index
<55 low or very low glycemic index

If a food has a high glycemic index (>70) it means that it is composed mainly of simple carbohydrates or that it has complex carbohydrates but little fiber, protein, and fat. Por lo tanto, la velocidad de absorción de este carbohidrato es alta. 

Foods with a medium glycemic index (55-69) contain mainly complex carbohydrates but are contained within a food matrix that is made up of fiber and protein. It could also be that it is a resistant starch. In any case, this food structure slightly slows down absorption. 

In the case of foods with a low glycemic index, we would refer to those that contain, in addition to carbohydrates, a large amount of fiber or proteins that make absorption very slow, favoring not having blood glucose peaks. 

The Diabetes Foundation of Spain makes available to the public a complete table of foods and their glycemic index.


The glycemic load is calculated by multiplying the glycemic index by the carbohydrates (in grams) contained in a serving of food and dividing the result by 100. If, for example, the glycemic index of watermelon is 72, a 100-gram serving of watermelon has 5 grams of carbohydrates available. How do we calculate it? By multiplying the 5 grams by 72 and dividing by 100:

5x 72 = 360
360 / 100 = 3,6 

We would say that the glycemic load of watermelon is 4. What does this mean? 

Low glycemic load is less than 10.

Medium glycemic load is between 11 and 19.

High glycemic load is greater than or equal to 20.

Thus, a 100-gram serving of watermelon has a low glycemic load. 


Because it helps to have an approximate idea (since the values are indicative) of the glycemic response of some foods. This is useful to avoid hyperglycemia after meals. It should be noted that, in the main meals of the day, we usually mix foods, so it is difficult to know exactly what the glycemic index is. 

Avoiding blood glucose spikes produced by a portion of food that has a very high glycemic index helps prevent diseases such as diabetes, heart disease, and other health conditions. In addition, it improves energy levels and concentration and helps to improve the levels of “good” cholesterol.


Cooking: the heat and hydration of food increase its glycemic index. Choose to cook al dente and try not to let the food cook so much that it becomes mushy.

Fiber: the more fiber a food has, the lower its glycemic index. This happens because the fiber containing a starch provides a barrier to the action of amylases and decreases absorption.

Maturation: remember to choose and consume fruits that are not too ripe because the riper they are, the higher their glycemic index will be.

Temperature: when we cook starch, the glycemic index rises, but if we then cool it, it falls. That is why it is recommended that, for example, rice and potatoes should be allowed to cool after cooking.

Combinations: combining foods with healthy fats and proteins is a way to lower the glycemic index because it causes less starch hydrolyzation.

The final consumption: food in its whole or chunked form, is absorbed more slowly by the body than in its liquid form. Therefore, tubers, fruits, and vegetables are best consumed in pieces or whole, and not in puree or juice.