gen-define-the-glycemic-index-and-give-one-short-worked-example-187e

Define the glycemic index and give one short worked example.

# Glycemic Index (GI) The **glycemic index** is a numerical scale (0-100) that ranks carbohydrate-containing foods based on how quickly they raise blood glucose levels compared to a reference food (pure glucose or white bread). - **High GI (70+)**: Rapidly digested and absorbed → sharp blood sugar spike - **Medium GI (56-69)**: Moderate effect on blood sugar - **Low GI (≤55)**: Slowly digested and absorbed → gradual blood sugar rise ## Worked Example **Food:** White bread (1 slice containing 15g carbohydrate) **Measurement process:** 1. A person fasts overnight, then eats 50g of pure glucose (reference food, GI = 100) 2. Blood glucose is measured over 2 hours and the area under the curve (AUC) is calculated = 300 units 3. On a different day, the same person eats enough white bread to provide 50g of carbohydrate 4. Blood glucose measured again over 2 hours; AUC = 210 units **Calculation:** GI = (AUC for white bread / AUC for glucose) × 100 GI = (210 / 300) × 100 = **70** **Interpretation:** White bread has a GI of 70 (high), meaning it raises blood sugar 70% as much as pure glucose and is rapidly absorbed.