The glycemic index, or GI, is a system of ranking carbohydrate foods on a scale of 0 to 100. These numbers quantify the degree to which a food raises blood sugar levels. A food with a high GI is one in which the body quickly digests and absorbs it, resulting in a rapid increase in blood sugar levels. Foods with lower GI values result in more gradual increases in blood sugar. Foods low on the GI also reduce insulin levels and insulin resistance.
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GI of Green Peas
Green peas, which contain 9 grams of carbohydrate per 150-g serving, are relatively low on the glycemic index, with a value of 22.
How to Measure GI
To identify where a food falls on the glycemic index, healthy individuals eat a sample of the particular food after an overnight fast. Researchers take finger-prick blood samples from the individuals every 15 to 30 minutes for two hours after the individual eats the food. The researchers then plot the blood sugar responses on a graph, yielding a blood sugar response curve. The area below the curve that is graphed is used to calculate the total increase in blood sugar levels after eating the food. The area under the curve is then divided by the area under the curve for a sample of the same amount of glucose, and multiplied by 100.
Glycemic Index Versus Glycemic Load
Blood sugar levels increase and then fall after you eat a meal with carbohydrates. The length of time your blood sugar remains elevated and the extent to which your blood sugar increases depends on the glycemic index of the food, and also how much of the food you eat. The glycemic load reflects both the glycemic index and the quantity of the carbohydrate-containing food in one value, and is valued as a tool to predict blood sugar levels after eating varying types and quantities of foods.
While adhering to a low-glycemic index diet may help diabetics control their blood sugar, Eating Well magazine notes that the measure is not foolproof. Different people absorb carbohydrates in different ways, and not all low-GI foods are necessarily healthy. Potato chips, with a GI of 54, qualify as low-GI, for example. The Glycemic Index and Load of a food is also variable depending on its level of fat, because fat facilitates food absorption.