Glycemic Index: Is it effective for blood sugar control?

picture showing a bread with low GI value

If you or your loved one have diabetes, I believe you have come across a term called “Glycemic Index”. Every time you go grocery shopping, you always look for a food labelled with “low glycemic index”, because you believe it is better for blood sugar control.

However, do you really understand the glycemic index, and is it truly effective in diabetic management? Or is there any more important aspect to consider?

The devil is in the details. This article will reveal the truth. 

What is Glycemic Index(GI)?

Glycemic Index, or GI, is a value used to determine how fast a specific food increases blood sugar level after it is eaten.

GI scoring range from 0 to 100, where white sugar has a score of 100. 

Put in a simple way, the faster the food raises blood sugar, the higher the GI. 


Low GI 

55 or less

Moderate GI

56 - 69

High GI

70 and above

photo shos a GI chart with some fruits beside

What affects a food’s GI value?

1. Fibre content

The higher fibre content in a food, the lower the GI.
Take white rice and brown rice as an example. Brown rice has germ and bran intact with it (high in fibre), which our body needs more effort to break them down and then only digest the rice. 

2. The level of processing

The food we eat is processed to some extent. However, the level of processing can be scaled from minimal to ultra-processed. In general, the more processing occurs in a food, the higher its glycemic index.

For example, instant oat has a higher GI than rolled oat, because it undergoes an extra cutting process which makes it into smaller flakes.  

3. Fat and protein content

Food that contains fat and/or protein tends to have a lower GI overall. Fat and protein have the effect of delaying gastric emptying, thereby reducing the speed of digestion and glucose absorption. (1)

This explains why a roti canai (high in fat) has a lower GI compared to white bread. 

4. Cooking time

Longer cooking time increase the glycemic index of a food. The carbohydrate started to break down when the food is heated.

For example, porridge has a higher GI than rice. 

5. Ripeness

The riper fruits tend to have higher GI value compared to their unripened counterpart.
This is because the amount of resistant starch (starch that “resists” digestion, thus helps in blood sugar monitoring) reduces in the process of ripening.

For example, a green(unripe) banana has a GI score of 30, while the GI of a yellow (ripe) banana is around 60. 

Is high-GI food always bad?

Before answer to this question, let me ask you:
An ice cream has a GI value of 60, and a cut of watermelon’s GI is 80,

Does it means ice cream is healthier than watermelon? Is ice cream a more appropriate choice for people with diabetes?

GI value of watermelon, ice cream and roti canai

Apparently not.

As mentioned above, a food’s glycemic depends on a lot of factors. In this case, ice cream contains a high amount of fat, thus it reduces the GI overall. Moreover, apart from the glycemic index, there is another pivotal factor that affects blood sugar - Glycemic Load(GL). 

What is Glycemic Load?

Besides GI, glycemic load take the amount of carbohydrate into account when measuring how quickly the food raises blood glucose level.

The formula of counting GL = ( GI x amount of carbohydrate) /100

For example, carrot is considered a high GI food with a value of 85. However, the amount of carbohydrates in a carrot is so low, making its glycemic load only equal to 4.3. (2)

Range of Glycemic Load 

Low GL

10 or less

Moderate GL


High GL

20 and above

Is the use of Glycemic Index effective in monitoring blood glucose?

It is not recommended to use GI as a tool in blood glucose monitoring.

First, according to the American Journal of Clinical Nutrition, individual responses of GI toward the same food can be a huge difference. (3) 

For example, by eating the same slice of white bread, one individual might experience a higher sugar rush than another, even if they both of them are healthy and have the same health condition. 

Besides, we usually do not eat just one food at one time. Many factors affect the glycemic index, like comparing eating just white rice, nasi lemak (rice cooked with coconut) or chicken rice - the glycemic index depends on the overall meal instead just solely the rice.
In addition, glycemic index does not truly reflect the quality of food. Like the topic we just discuss, some food might have a high GI (like some fruits) but are nutritious, while some foods that are not so suitable for people with diabetes have a low GI. Instead of focusing on GI, it is recommended to focus more on “nutrition-dense” food.

glycemic load formula

How about GL if GI seems not so effective?

Compared to GI, GL tells more story as it takes the amount of carbohydrates in a serving of food into account. While it can be a better tool than GI, it has the same downside, which is it cannot determine the quality of food.

Besides, it is more complex and is generally less practiced than GI. The GL value of food is harder to find. Thus, it increases the hindrance for people in choosing what to eat.

Bottom line

The concept of the glycemic index is getting more common in Malaysia. This can be shown in more food packaging are labelled with GI value, especially bread.

It cannot be denied that both glycemic index and glycemic load play a part in controlling blood sugar. However, we need to consider beyond that. It is important to pay attention to your own body, and how it reacts to a particular food, instead of just blindly following the numbers. 

a basket full of groceries placed at the centre of aisle


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