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How Do Laboratories Measure a Food’s Glycemic Index (GI) or GI Value?

By measuring the GI values of foods, laboratories provide essential information that guides dietary choices, supports diabetes management, and promotes overall health.

by | Jan 15, 2023

Need food laboratory for glycemic index GI testing?

Need a food laboratory for glycemic index GI testing?

The glycemic index (GI) is a ranking system that measures how quickly carbohydrates in foods raise blood glucose levels after consumption. It is an essential tool for understanding how different foods impact blood sugar and can help individuals manage diabetes, maintain healthy blood sugar levels, and make informed dietary choices. As the demand for healthier food options increases, food manufacturers and researchers are turning to food glycemic index testing to accurately determine the GI values of various foods. This article explores how laboratories measure a food’s glycemic index, the importance of GI testing, and its role in nutrition and health.

What is the Glycemic Index (GI)?

The glycemic index (GI) is a numerical scale ranging from 0 to 100, used to rank carbohydrate-containing foods based on their impact on blood glucose levels. Foods with a high GI value (70 or above) cause a rapid spike in blood glucose, while foods with a low GI value (55 or below) result in a slower, more gradual increase. Foods with a moderate GI fall between these two ranges.

Importance of Glycemic Index Testing

1. Managing Diabetes:
For individuals with diabetes, understanding the GI of foods is crucial for managing blood sugar levels and preventing spikes that can lead to complications. Low-GI foods are often recommended as they provide a slower and more stable release of glucose.

2. Weight Management:
Foods with a lower GI value tend to promote satiety and reduce hunger, helping individuals manage their weight more effectively. By incorporating low-GI foods into their diets, people can better control appetite and avoid overeating.

3. Reducing the Risk of Chronic Diseases:
Consuming low-GI foods has been linked to a reduced risk of chronic diseases such as heart disease and type 2 diabetes. By testing and choosing foods based on their GI values, individuals can make dietary choices that support long-term health.

4. Informed Food Choices:
Glycemic index testing provides valuable information to consumers, allowing them to make informed choices about the foods they eat. It also helps food manufacturers develop and market products that cater to health-conscious consumers.

How Laboratories Measure a Food’s Glycemic Index (GI) or GI Value

Glycemic index testing involves both in vivo (human-based) and in vitro (laboratory-based) methods. While in vivo testing is considered the gold standard, in vitro methods are also widely used due to their practicality and efficiency. Here’s how laboratories typically measure a food’s glycemic index:

1. In Vivo Glycemic Index Testing (Human-Based Testing):

In vivo testing involves feeding human subjects a portion of the food being tested and measuring their blood glucose response over a specific period. The process includes the following steps:

  • Subject Selection:
    A group of healthy human subjects, usually between 10 to 12 individuals, is selected for the test. These subjects should have normal blood glucose levels and no metabolic disorders.
  • Fasting and Baseline Measurement:
    Subjects fast for 10-12 hours before the test to ensure baseline blood glucose levels. After fasting, their baseline blood glucose levels are measured.
  • Test Food Consumption:
    Each subject consumes a portion of the test food containing a specific amount of carbohydrates (typically 50 grams). The portion size is adjusted based on the carbohydrate content of the food.
  • Blood Glucose Measurement:
    Blood glucose levels are measured at regular intervals (e.g., every 15, 30, 45, 60, 90, and 120 minutes) after consuming the test food. The area under the curve (AUC) of blood glucose response is calculated over the two-hour period.
  • Reference Food Comparison:
    The test is repeated with a reference food, such as glucose or white bread, which is assigned a GI value of 100. The AUC for the test food is compared to the AUC of the reference food to calculate the GI value of the test food.
  • Calculation of GI Value:
    The GI value is calculated using the formula:

    GI=(AUC for reference food / AUC for test food)×100
    The resulting GI value indicates how the test food affects blood glucose levels relative to the reference food.

2. In Vitro Glycemic Index Testing (Laboratory-Based Testing):

In vitro testing methods simulate the digestive process in a controlled laboratory environment to estimate the GI value of foods. This approach is less expensive and time-consuming compared to in vivo testing. The steps involved in in vitro testing include:

  • Simulated Digestion:
    The test food is subjected to enzymatic digestion using digestive enzymes such as amylase and protease to mimic the breakdown of carbohydrates in the human digestive system. This process releases glucose from the food.
  • Glucose Release Measurement:
    The amount of glucose released from the food is measured over time using biochemical assays. This measurement provides an estimate of the food’s carbohydrate digestion rate.
  • Comparison with Reference Food:
    The glucose release profile of the test food is compared with that of a reference food, such as glucose or white bread, to estimate the GI value.
  • GI Estimation:
    Based on the glucose release profile and comparison with the reference food, an estimated GI value is calculated. While in vitro testing provides useful estimates, it may not fully capture the complexities of human digestion and absorption.

The Role of GI Testing in Nutrition and Health

Glycemic index testing provides valuable insights into how foods affect blood sugar levels and can guide dietary recommendations and product development. Here are some key roles of GI testing:

1. Guiding Dietary Recommendations:
Nutritionists and dietitians use GI values to create dietary plans that help individuals manage blood sugar levels, control weight, and reduce the risk of chronic diseases. GI testing supports the development of evidence-based dietary guidelines.

2. Product Development and Labeling:
Food manufacturers use GI testing to develop products that meet consumer demand for healthier options. Products with low GI values can be marketed as suitable for individuals with diabetes or those seeking to manage their blood sugar levels. Accurate GI labeling helps consumers make informed choices.

3. Enhancing Consumer Awareness:
Glycemic index testing educates consumers about the impact of different foods on blood sugar levels. By providing information on GI values, consumers can make informed choices that align with their health goals.

4. Supporting Research and Innovation:
GI testing contributes to research on the health effects of carbohydrates and helps identify dietary patterns that promote health and well-being. It supports innovation in food science by encouraging the development of foods with lower glycemic responses.

Conclusion

Glycemic index testing is a valuable tool for understanding how foods impact blood glucose levels. By measuring the GI values of foods, laboratories provide essential information that guides dietary choices, supports diabetes management, and promotes overall health. Whether through in vivo or in vitro methods, GI testing helps consumers, healthcare professionals, and food manufacturers make informed decisions that contribute to a healthier future.

For more information on food glycemic index testing and to connect with expert testing laboratories, visit ContractLaboratory.com. Ensure your products meet consumer expectations and health standards with accurate and reliable GI testing services.

NEED FOOD GLYCEMIC INDEX TESTING?

Common food products needing Glycemic Index testing include breads, cereals, cookies, cakes, and bakery products. If you are a food manufacturer, distributor, importer, retailer, or restaurant in need of a food laboratory for glycemic index testing, Submit a Food Request on our website or Contact Us for more information.

Author

  • Trevor Henderson BSc (HK), MSc, PhD (c), is the Creative Services Director for the Laboratory Products Group at LabX Media Group. He has more than three decades of experience in the fields of scientific and technical writing, editing, and creative content creation. With academic training in the areas of human biology, physical anthropology, and community health, he has a broad skill set of both laboratory and analytical skills. Since 2013, he has been working with LabX Media Group developing content solutions that engage and inform scientists and laboratorians.

    View all posts Director, Creative Services - LabX Media Group

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