Glycaemic index testing

We measure glycaemic index (GI) according to the agreed international convention (WHO/FAO 1998) on foods, beverages, food components and specialised food formulations. We have nearly 10 years’ experience and practice in GI measurement and offer a flexible and user-orientated service.

We will measure the GI of single components, single foodstuffs or whole batches of related components or products.

• Read more about GI and the health benefits of low-GI diets

Our GI measurement service has the following key features:

• Rapid turnaround times, using a panel of calibrated and healthy individuals
• Accurate glucose analysis equipment
• Client access to data and analysis through the secure area of this website
• All reports vetted by our technical experts
• Guaranteed dates and times of testing
• Competitive charges with discounts for large batches of products

We are proud of our service quality and encourage our partner clients to observe any part of the testing process. The secure area of our website allows clients to view results as they emerge and be reassured of adherence to planned schedules of testing. We can usually offer a turnaround time of less than a week for runs of one or two items. We have the necessary food handling, food storage and food preparation facilities to ensure products are tested in their optimum condition.

Use of volunteers
Current convention requires the use of human volunteers to measure the GI of foodstuffs or food components. We have a panel of volunteers from whom we assemble a cohort for a particular series of tests. All our volunteers have been screened for confounding clinical conditions and we are able to respond rapidly to client requirements.

Volunteers have their normal glucose response measured in two separate tests when they join the panel and have confirmatory tests to ensure their baseline response is valid and up-to-date. These baseline measurements use either a standard glucose preparation or an equivalent portion of white bread of known GI. The actual testing protocol can be viewed below.

Client reports
HFR provides the client with two expert reports. The first is a preliminary report that is available within days of the testing. Within a month of completion of testing, a final report will be provided that will detail the test results and have an expert interpretation of the findings. We will document the methodology to provide a full record of the testing service provided.

Our fee structure allows for the production of the final report but any additional presentation of results or further discussion of implications attracts a consultancy fee.

• Read more about our consultancy service

For clients wishing to demonstrate their GI testing was carried out by HFR we can provide a mark that may be added to product packaging and labelling. This shows that the testing has been carried out by HFR and according to standard testing protocols. Please enquire if you require this service.

Testing protocol for calibration
The volunteer is required to be in a fasting state, having had no food or drink other than water for the eight hours prior to testing. We measure their blood glucose level twice, once 15 minutes prior to asking the volunteer to consume the standard glucose dose and once again just before they do so. The mean of the two readings is the natural level of blood glucose.

After the volunteer has consumed the standardised glucose preparation, we then measure blood glucose levels every 15 minutes for the next hour and twice in the following hour.

With this data we can construct a dose response pattern for the volunteer and this is their calibration.

Testing protocol for GI measurement
A panel of between ten and 12 volunteers with valid calibration measurements is assembled at an agreed time. Each panel member is in a fasting state, having consumed no food or drink in the preceding eight hours. We measure their blood glucose levels 15 minutes prior to consuming the product under test and again just before consumption.

The volunteers consume the test product, in the formulation specified by the client. They are asked to consume it as quickly as possible.

We measure their blood glucose levels every 15 minutes for the first hour and every 30 minutes for the next hour. We construct a plot of glucose levels against time and estimate the enclosed area. The ratio of this area to that under the calibration plot yields a comparison for each individual. The average of ten individuals’ ratios is the measurement of glycaemic index.