GI Update

Professor Jennie Brand-Miller answers your questions

Does the carbohydrate content on a food’s nutrition label have any relationship to its blood glucose-raising capacity?
Yes, but only to some extent. We can make a few generalisations. If a food has less than 5 grams of carbohydrate per serving, then it won’t have a marked effect on your blood glucose levels. If it has 10 or more grams it’s likely to have a substantial effect, depending on the food’s GI value. So all the label can tell you is whether the food is high or low in carbohydrate. If the food is high in carbohydrate, then its GI is much more relevant. A food that’s both high in carbohydrate and has a high GI could be contributing to high blood glucose readings.

    Studies tell us that diets based on frequent consumption of high GI value carbohydrates will put us at greater risk of developing type 2 diabetes, heart disease and some forms of cancer. It’s not the amount of carbohydrate that matters, it’s the source. High carbohydrate diets from high GI sources spell trouble, especially for people with insulin resistance, which is one of the underlying causes of type 2 diabetes. That’s why we believe that any changes to front-of-pack food labelling schemes must move beyond the current focus on added sugars and include the glycemic impact of the food’s carbohydrates if our government health departments are really concerned about reducing the risk of type 2 diabetes.

    In our most recent paper published in the American Journal of Clinical Nutrition, we showed that the glycemic load of food may be more effective than the available carbohydrate content in calibrating how much insulin patients with type 1 diabetes should take before meals. In two studies, glycemic load repeatedly outperformed carb content in predicting the increase in blood glucose and insulin levels up to two hours after eating in 10 healthy young people who consumed 121 types of single foods (study 1) and 13 mixed meals (study 2).

    GI testing by an accredited laboratory
    North America

    Dr Alexandra Jenkins
    Glycemic Index Laboratories
    20 Victoria Street, Suite 300
    Toronto, Ontario M5C 298 Canada
    Phone +1 416 861 0506

    Fiona Atkinson


    Research Manager, Sydney University Glycemic Index Research Service (SUGiRS)
    Human Nutrition Unit, School of Molecular and Microbial Biosciences
    Sydney University
    NSW 2006 Australia
    Phone + 61 2 9351 6018
    Fax: + 61 2 9351 6022

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