• Q&A with Australian Health Practitioners

    What is the difference between Glycemic Index (GI) and Glycemic Load (GL)?

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    The Glycemic Index Foundation (GIF) is a not-for-profit company supported by The University of Sydney and JDRF (Australia). GIF is committed to providing Australians with ... View Profile

    Your blood glucose rises and falls when you eat a meal containing carbohydrates. How high it rises and how long it remains high depends on the quality of the carbohydrates (the GI) and the quantity. Glycemic load or GL combines both the quality and quantity of the carbohydrate.

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    Courtney Bates

    Dietitian, Nutritionist



    Courtney is an Accredited Practising Dietitian (APD), Accredited Nutritionist (AN) and member of the Dietitians Association of Australia (DAA). She runs her own practice on ... View Profile

    In addition to The GIF's great explanation above; a take home message I often tell my clients is that even though a food may be slowly absorbed, or low glycaemic index (GI), if you eat a large quantity it can still cause your blood sugar level to spike as you are eating a high glycaemic load (GL).

    There are 2 principles to consider.
    1. Choose low GI foods (e.g. sweet potato, quinoa, wholegrain bread, fruits)
    2. Keep the glycaemic load in check by watching the portion size of your low GI carbohydrates.

    Remember 1 slice of bread = 1/3 cup cooked quinoa, 1/2 cup sweet potato or 1/2 cup fruit salad. An APD can calculate more accurately how much carbohydrate you should have at each meal or snack. A general rule of thumb is to fill 1/4 of your plate with low GI carbohydrates.

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    Dr Kate Marsh

    Diabetes Educator, Dietitian



    Kate Marsh is an Advanced Accredited Practicing Dietitian and Credentialled Diabetes Educator working in private practice in Sydney. Kate has a PhD, Masters of Nutrition ... View Profile

    The glycemic index of a food is a measure of the rate at which the carbohydrate from food is broken down into glucose in your bloodstream.  While choosing low GI foods has many benefits, the overall effect that a food has on blood glucose levels is dependent on both the nature (GI) of the carbohydrate it contains and the amount (ie grams of carbs).  Glycemic load takes both of these factors into account.. 
    While foods with a high carbohydrate content and those with higher GI values will generally have the highest GL, this also means that small amounts of a high GI food may have only modest effects on blood glucose levels while, as Courtney points out above, large amounts of a low GI food can still raise blood glucose and insulin levels significantly.  What this means in practice, is that there is no need to avoid foods that have a high GI but are low in carbohydrate and nutrient-dense. On the other hand, just because a food is low GI, it doesn’t mean you can eat as much as you like, particularly if you are watching your weight or your blood glucose or insulin levels.

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