Glycemic Index (GI) Definition
The Glycemic Index (GI) is a numerical ranking system that measures how quickly carbohydrate-containing foods raise blood glucose levels compared to pure glucose or white bread as a reference food.
Understanding GI Values
Foods are ranked on a scale from 0 to 100:
- High GI foods: 70 or above
- Medium GI foods: 56-69
- Low GI foods: 55 or below
Pure glucose is given a reference value of 100, and all other foods are measured relative to this standard.
How GI Works
When you consume carbohydrates, your body breaks them down into glucose, which enters your bloodstream. The GI tells us:
- How quickly this process happens
- How dramatically it affects your blood sugar levels
If you eat white bread (high GI ≈ 75), your blood glucose levels will rise quickly and sharply. If you eat lentils (low GI ≈ 32), your blood glucose levels will rise more slowly and steadily.
Think of GI like a speed indicator - high GI foods are like sprinters (fast spike in blood sugar), while low GI foods are like marathon runners (steady, sustained energy release).
Factors Affecting GI
The GI value of a food can be influenced by several factors:
- Physical form (liquid vs solid)
- Ripeness (especially in fruits)
- Processing method
- Fiber content
- Fat content
- Protein content
Many people assume that all sugary foods have a high GI and all complex carbohydrates have a low GI. This isn't always true - some fruits have lower GI values than certain whole grain products.
When studying GI, remember that it's just one aspect of a food's nutritional value. A food with a low GI isn't necessarily more nutritious than a food with a high GI.
[A diagram showing a graph with two lines: one showing the sharp spike in blood glucose after consuming a high GI food, and another showing the gradual rise and fall with a low GI food. X-axis shows time, Y-axis shows blood glucose levels.]
