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What is glycemic index?

The glycemic index is a scale of measurement used to determine the impact of a certain food on the body’s blood glucose levels. The glycemic index ranges from 0 (low glycemic index) to 100 (high glycemic index). The higher the glycemic index score the more likely blood glucose levels will rise in response to a certain food eaten and absorbed by the body.

How is glycemic index calculated?

The glycemic index concept provides a numerical value to food to represent the effect of the food on blood glucose level. Glycemic index measures the increase in blood glucose level above baseline (fasting) level during a 2-hour period following consumption of the food.

These values are then compared with the increase in blood glucose levels during a 2-hour period following ingestion of the same amount of carbohydrate in a reference food (usually white bread or glucose).

What are the limitations in using glycemic index?

There are several other factors to consider besides glycemic index when assessing how a food will impact blood glucose levels. For instance, the composition of a meal can cause much variation in blood glucose response. Eating a meal high in fiber, protein, and fat can make a high-glycemic index food have a low-glycemic index response. This is because fiber, protein, and fat help slow down the digestion and absorption of glucose into the blood. Other factors such as food form, ripeness, location of growth, and variety can all impact the rate of elevation in blood glucose. While glycemic index can be a good starting place for learning what foods might raise blood sugar quickly, it is important to also consider these other factors when choosing foods.

What fruits have a low glycemic index?

Fruit is considered a nutrient dense food, meaning it offers several nutrients considering the amount of calories. Although fruits are a type of carbohydrate, this doesn’t necessarily mean that eating fruit will greatly increase blood glucose. Most fruits actually have a low glycemic index. Dried fruit, melons, and pineapple are exceptions, as they have a medium glycemic index. Especially when eaten in typical portion sizes, such as a medium apple or ½ cup of blueberries, fruit is an essential part of a healthy diet.

Related Terms

Macronutrients Glucose

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Photo of Kristin Ricklefs-Johnson

Medically reviewed by:

Kristin Ricklefs-Johnson, Ph.D., RD

Kristin is an RDN who also earned her Ph.D. in Nutrition from Arizona State University with an emphasis on insulin resistance, lipid metabolism disorders, and obesity. She completed her post-doctoral fellowship at Mayo Clinic where she focused on nutrition-related proteomic and metabolic research. Her interests include understanding the exact mechanism of action of various genetic variations underlying individual predispositions to nutrition-related health outcomes. Her goal is to help all individuals prevent chronic diseases and achieve long, healthy lives through eating well.

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