When it comes to diabetes management, understanding terms like glycemic index and glycemic load is crucial. The following article discusses these terms in detail and explains their importance in managing diabetes.
Table of Contents
How the Term ‘Glycemic Index’ Came into Existence?
Carbohydrates can be classified as simple or complex based on the number of simple sugars present in a molecule. For example, carbohydrates containing two simple sugars (glucose), such as fructose and sucrose (table sugar), are called simple sugars. On the other hand, carbohydrates containing long chains of glucose, such as starch, are considered complex carbohydrates. In the past, it was advised to consume more complex carbohydrates than simple carbohydrates because it was believed that complex carbohydrates, with their long chains of glucose, would raise blood sugar more slowly than foods containing simple carbohydrates.
However, this assumption is not true for many foods containing complex carbohydrates. It has been found that some foods with complex carbohydrates raise blood sugar rapidly. In other words, the tendency to raise blood glucose varies from one food to another within the complex carbohydrate category. The concept of the glycemic index was developed to classify dietary carbohydrates based on their overall effect on postprandial (after-meal) blood glucose levels compared to a reference carbohydrate, such as glucose.
Carbohydrate-containing foods that are easily digested are more likely to increase blood sugar quickly. Conversely, foods containing carbohydrates that are not easily digested do not raise blood sugar as swiftly. In other words, easily digested and metabolized carbohydrates have a high GI compared to slowly digestible carbohydrates.
What is Glycemic Index
The Glycemic Index (GI) is a method used to rank foods, especially carbohydrates, based on how they impact your blood glucose levels. It was originally created to help people with diabetes select foods for better glycemic control. “Glycemic” refers to glucose (sugar) in the blood, and “index” refers to a numerical scale used for measurement. In other words, the glycemic index indicates how quickly a carbohydrate-containing food raises blood glucose levels. The blood glucose level is compared to pure glucose, which has a GI of 100.
Glycemic Index Chart
| Low Glycemic Index | (≤55) |
| Moderate Glycemic Index | (56-69) |
| High Glycemic Index | (≥70) |
| Glycemic Index of Pure Glucose | 100 |
How to Measure Glycemic Index of Food?
Take 50 grams of pure sugar dissolved in water on an empty stomach (having fasted for at least 12 hours). Measure the blood glucose level every 5 minutes for 2 hours. Below is a graph of the blood glucose levels of a normal person who consumed 50 grams of sugar in water and measured their blood glucose levels for 2 hours.
The graph shows a pretty rapid spike in blood glucose. The blood sugar peaks at around 45 minutes after taking the drink and normalizes back at around 75 minutes.
The next day, a test food is consumed to measure the glycemic index of carbohydrates. In this example, 50 grams of brown wheat bread slices are taken as a source of digestible carbohydrates. Therefore, in this example, a normal individual consumes 3 slices of brown bread. The following graph shows the graphs for both the sugar drink and wheat bread consumption.
It is pretty striking how different the graph curves are over the two hours. The bread causes a much more gradual rise in blood glucose, and the peak is essentially lower than with the sugar drink. The Glycemic Index (GI) is calculated as the area under the glucose curve after the test food is consumed, divided by the area under the glucose curve after the control food (glucose drink) is consumed. The value is then multiplied by 100 to represent a percentage of the control food.
In the above example, the GI of brown bread comes to 34. It means, brown wheat bread elevates only 34% blood sugar level compared to sugar drink. It means, brown wheat flour has a low glycemic index.
What is Glycemic Load (GL)?
It is frequently recommended to eat low-GI foods for health. The glycemic index is a method used to categorize food based on how they impact your blood glucose levels. In other words, if you want to avoid high blood glucose levels, then you should avoid high-GI foods. However, it’s important to note that the GI is calculated based on the consumption of 50 grams of food, which could be much more than what you usually consume.
For example, to calculate the GI of brown bread, you would need to consume 3 full-sized bread slices, which is more than you might typically eat for breakfast. Similarly, watermelon has a high GI of 76, but to calculate its GI, you would need to consume 4 and a half cups of watermelon, which is equivalent to a whole fruit and not practical to consume in one go.
To address this limitation, the concept of glycemic load (GL) was introduced. GL is a ranking system that adjusts the GI for the number of carbohydrates in a typical serving size. To calculate GL, you can use the following formula:
You know that watermelon has a high GI of 76, but it’s mostly water. A typical 100 gram of watermelon has only 7 grams of digestible carbs. So, you can calculate the GL of watermelon as follows:
Low, Intermediate and High Glycemic Load
| High GL value | ≥20 |
| Intermediate GL value | 11 – 19 |
| Low GL value | ≤10 |
Glycemic Load is a better reflection of expected blood glucose responses to foods based on how much you usually eat in a serving. That makes it more useful than the glycemic index. Dietary GL is the sum total of all the GLs for all foods consumed in the diet.
GI and GL Chart of Different Food Items
| Food item | GI | Serving Size | Carbohydrate per serving | GL per serving |
| Doughnut | 76 | Medium | 23 | 17 |
| Watermelon | 76 | 1 cup full | 11 | 8 |
| White boiled Rice | 66 | 1 cup | 53 | 35 |
| Table Sugar | 63 | 2 tsp | 10 | 6 |
| Spaghetti | 58 | 1 cup | 44 | 25 |
| White bread | 71 | 1 slice | 14 | 10 |
| Raw orange | 42 | 1 medium | 11 | 5 |
| Raw apple | 39 | 1 medium | 15 | 6 |
| Raw Pear | 38 | 1 medium | 11 | 4 |
| Boiled carrots | 33 | ½ cup | 4 | 1 |
| Cashew | 25 | 1 oz | 9 | 2 |
| Peanuts | 18 | 1 oz | 6 | 1 |
| Pure Honey | 58 | 1 Tbsp | 17 | 10 |
How to Lower Dietary Glycemic Load?
It is important to consider food with low GI and GL. There are a few strategies that can be used to lower dietary glycemic load:
- Add more nuts, legumes, whole grain, and fruits in your diet
- Lower the consumption of starchy and high GI foods such as white bread, white rice and potatoes, to name only a few.
- Lower the consumption of foods containing sugars such as soft drinks, cookies, etc.
FAQs (Frequently Asked Questions)
Q. What makes blood glucose rise in a diet?
A. In foods, carbohydrates are most specifically responsible for raising the blood glucose level.
Q. What should be the total glycemic load for a day?
A. The daily glycemic load should be less than 100 for optimal health.
Q. What is a good glycemic index for diabetics?
A. The glycemic index should be less than 55.
