The Glycemic Index(GI) is the measure of how quickly a food(which has 50 grams of carbohydrates) can raise your blood sugar levels. It is measured on a scale of 0 to 100 and is proportional to the amount of carbohydrates that the food has. A GI of 0 means the food has a negligible amount of carbohydrates, while a value of 100 is assigned to pure glucose.
Typically, food sources with a high amount of carbohydrates, such as cereals like rice (GI 90), wheat (GI 53), and corn(55-79) have a high GI, while legumes, pulses(lentils), and animal products like chicken (GI 0) and fish (GI 0) have a low GI.
This index should be used with a Glycemic Load chart, which takes the amount of carbohydrates in food as well to calculate a more comprehensive way of categorizing foods.
You can check out the list of foods with their GI values.
How is the Glycemic Index Calculated?
The Glycemic Index is calculated as the integral area under the glucose rise curve after eating approximately 50 grams of carbohydrates. The diet must have taken place after a 12-hour fasting period, and the person should be non-diabetic.
This area is then divided by the area under the curve obtained under similar conditions (12-hour fast) but after having glucose equivalent to 50 grams of carbohydrates.
Understanding High, Moderate, and Low GI Values
Typically, the following values are used everywhere for dividing foods as per the glycemic index.
- High – 70 to 100
- Moderate – 55 to 70
- Low – 0 to 55
However, I use a slightly modified classification to compensate for higher meal portions. This is because, unlike Western countries, in which the previous classifications have arisen, Asian countries generally consume much more food. Hence, if the above classification is used in an Asian context, we might increase our blood glucose.
The new modification relies on the assumption that a low-GI food from this list will not significantly increase blood sugar levels even if the person eating it has high levels of blood sugar (PPBS: 300-350).
High Glycemic Index Foods
These are the foods that will quickly raise your blood sugar levels, and diabetics without medication can land them in serious trouble.
Though there is a convention of keeping those foods with a higher GI than 70 in this category, our classification categorizes high-GI foods as those with GI values higher than 55. This is because, below 55, the foods are much healthier and relatively safer for all kinds of diabetics.
Moderate Glycemic Index
Foods with a Glycemic Index value of 55-70 are categorized as moderate GI foods.
However, in our classification, we put them between GI values of 30-55.
Low Glycemic Index
Foods with GI values of 55 or lower are called low GI foods.
At Health Tips on Cloud, we categorize foods with GI values lower than 30 as low GI foods.
Glycemic Index and Glycemic Load Charts
GI Values Change With Ripeness, Cooking, and Processing
The Glycemic index of foods varies with the time of cooking, the degree of processing that the food goes through, and the ripeness of that fruit.
With cooking, the complex fibers and molecules break down into more simpler fibers and carbohydrates. This makes digestion easier and hence, the blood glucose is raised quickly.
Further, with the degree of processing, there is an increase in the time it needs to break down the food, and hence processing leads to a higher GI value, For example, whole wheat flour, which is a more processed form of wheat has a GI value of 53-60 while bulgur or broken wheat has a lower GI of 46.
Further, the third thing that increases the GI value is the degree of ripeness. More ripe fruits and vegetables have a higher GI compared to the raw ones. This is true for both vegetables and fruits. Therefore, for diabetics, it is always advised that we eat less ripe fruits and vegetables.
A rule of thumb for this could be, that the more chewy the food, the lower will be its GI.
How to Estimate the GI of Processed Foods
You might not get an exact value while testing at home, but you will get a brief idea that is enough for awareness.
To estimate the GI of processed foods:
- Check ingredients: Foods with refined carbs (e.g., white flour, sugar) typically have a higher GI.
- Fiber content: High-fiber foods usually lower GI.
- Fat and protein: These slow digestion and lower GI.
- Cooking method: More processed/cooked foods usually have higher GI.
- Compare with known GI values: Use online GI databases for similar foods.
Which GI Value is Good For Diabetes?
Diabetics should keep their diet restricted to low GI foods irrespective of whether they are on medication or not.
The first reason is that low GI foods will help them lose body weight which is one of the key contributors to high blood sugar levels.
Secondly, low-GI food will prevent them from gaining weight. This is because medicines for diabetics help you digest more food. Since you are digesting more food, more carbs are getting absorbed in your blood. This then increases your body weight.
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Using Glycemic Index with Glycemic Load
When assessing the impact of foods on blood sugar levels, it is essential to consider both the Glycemic Index (GI) and Glycemic Load (GL). While GI measures how quickly a food raises blood sugar, GL provides more comprehensive insight by taking into account both the speed and the quantity of carbohydrates released into the bloodstream.
Why Glycemic Load Matters
Complete Picture: GL values offer a fuller understanding of how much your blood sugar levels will rise and how long they will remain elevated after consuming a particular food.
Hidden Risks: Foods with a moderate GI but a high GL can be just as harmful for diabetics as foods with a high GI alone.
High GI, Low GL Foods
These foods tend to release carbohydrates into the bloodstream quickly, but only for a short period of time, causing a brief spike in blood sugar.
Some foods have a high GI but a low GL because they contain lower amounts of carbohydrates.
