The Glycemic Index (GI) is a relative ranking of carbohydrate in foods according to how they affect blood glucose levels. Foods are ranked on a scale of 0 to 100, with pure sugar (Glucose)A given a value of 100. The lower a food’s glycemic index, the slower blood sugar rises after eating that food. The ability of the food item to raise the blood sugar is measured in terms of the Glycemic Index.
The classification of foods depending on the glycemic index is as follows:
Low GI foods: 55 or less
Moderate GI foods: 56 to 69
High GI foods: 70 and above
A number of factors can influence the GI value of a food or meal, including:
- The type of sugar: It’s a misconception that all sugars have a high GI. The GI of sugar actually ranges from as low as 19 for fructose to up to 105 for maltose. Therefore, the GI of a food partly depends on the type of sugar it contains.
- Structure of the starch: Starch is a carbohydrate made up of two molecules, amylose, and amylopectin. Amylose is difficult to digest, whereas amylopectin is easily digested. Foods with a higher amylose content will have a lower GI
- How refined the carbohydrate is: Processing methods such as grinding and rolling disrupt amylose and amylopectin molecules, raising the GI. Generally speaking, the more processed a food is, the higher its GI
- Nutrient composition: Both fat and acid slow down the rate at which a food is digested and absorbed, resulting in a lower GI. Adding fats or acids, such as avocado or lemon juice, will lower the GI of a meal.
- Cooking method: Preparation and cooking techniques can change the GI too. Generally, the longer a food is cooked, the faster its sugars will be digested and absorbed, raising the GI.
- Ripeness: Unripe fruit contains complex carbohydrates that break down into sugars as the fruit ripens. The riper the fruit, the higher its GI. For example, an unripe banana has a GI of 30, whereas an overripe banana has a GI of 48
Some other factors affecting the glycemic response to food include:
- Rate of ingestion
- Food form
- Food components
- Methods of cooking and processing food
- Physiologic response
Choosing low GI foods can particularly help manage glucose levels in people with Type 2 diabetes. Not all low GI foods are healthy choices – chocolate, for example, has a low-GI because of its fat content, which slows down the absorption of carbohydrate.
Combining foods with different GIs alters the overall GI of a meal. You can maximize the benefit of GI by switching to a low GI option with each meal or snack.
Swaps for lowering glycemic index
|Instead of this high glycemic index food||Eat this lower glycemic index food|
|White rice||Brown rice or parboiled rice|
|Instant oatmeal||Steel-cut oats|
|White bread||Whole-grain bread|
|Corn||Peas or leafy greens|
|Fruit roll-up||Whole fruit|
Few healthy low-GI snack ideas:
- A handful of unsalted nuts
- A piece of fruit
- Carrot sticks with hummus
- A cup of berries
- Yogurt with fruit/nuts
- Apple slices with almond butter or peanut butter
- A hard-boiled egg