Advanced GI testing and food physiological services
The glycaemic index testing service has been in operation since 2004 since then we have carried out testing numerous food products. There is a hard working team lead by Dr Shelagh Hampton.
The University of Surrey
The Nutritional Sciences Department located within the Faculty of Health and Medical Sciences(FHMS) at the University of Surrey is ranked within the top three UK Universities for teaching and research in the field of Dietetics, Nutrition and Food Science. Our Henry Wellcome Nutritional Sciences Research Laboratories provide all the up to date technologies for the assessment of nutritional status at the macro and micronutrient level including a fully support mass spectrometry suite housing five mass spectrometry for measurement of stable isotopes. Nutritional Sciences Laboratories also house a state of the art iLAB, cell culture facilities as well a fully equipped freezer storage. Within FHMS, our facilities include functional genomics, proteomics and metabonomics suites. The University of Surrey Glycaemic Index testing service is embedded within this department and can draw upon a substantial amount of the experience.
Types of Testing:
Protocol and Methods
- The WHO/FAO protocol is used.
- The Ethics committee at the university has approved the procedure.
- Testing is carried out in our special clinical unit.
- Ten healthy subjects are recruited.
- Each subject is studies 5 times for one product.
- The test food/beverage has to be investigated twice and the reference food has to be investigated three times. It has been shown that it is necessary to repeat the reference food greater than twice to reduce the variation of the mean GI value since the reference data is used to calculate the test food/beverages GI.
- Subjects are studied for 2h each time with seven finger prick samples.
- Glucose analysis is carried out on the YSI glucose analyser. Three reference values are run per set of three subjects to ensure no drift in results.
- Insulin can also be measured on samples which will enable the insulineamic index of the food/beverage to be calculated.
- When large numbers of food products are tested glucose references are carried out every five food items.
- The carbohydrate content on the package is used to calculate the amount of carbohydrate to use unless the client would like the food composition assessed which we can do if requested. We have successfully assessed a number of meals previously in this way
- Lipids such as cholesterol, triacylglycerol and non-esterified fatty acid can also be measured.
- Satiety can be monitored using an electronic diary. We have validated these diaries and utilise them in many projects. These diaries reduce inaccuracies associated with paper diaries such as transposition errors. The diaries randomise the order so no order effects are present.
Continuous Glucose Monitoring System
- Glucose monitors are available that display interstitial blood glucose every 5 minutes via a glucose sensor.
- Can be worn for 5 days continuously
- Enable continuous glucose profiles to be obtained throughout the day even during exercise and sleep
University of Surrey is pleased to provide its clients with a report which states the clinical testing has been carried out by University of Surrey Glyceamic Index testing service .
Al-Mssallem MQ, Hampton SM, Frost GS and Brown JS (2011) A study of Hassawi rice (Oryza sativa L.) in terms of its carbohydrate hydrolysis (in vitro) and glycaemic and insulinaemic indices (in vivo)." Eur J Clin Nutr 65(5): 627-34.
Morgan LM, Shi JW, Hampton SM, Frost G (2011) Effect of meal timing and glycaemic index on glucose control and insulin secretion in healthy volunteers. Br J Nutr. 2012 108(7):1286-91.
Gibbs M, Harrington D, and Hampton SM(2009) Diurnal variation in glycaemic response to a low and high glycaemic index mixed meal. Proceeding of the Nutrition Society 68: E101
Wolever et al (2008) Measuring the glycemic index of foods: interlaboratory study. Am J of Clin Nut 87(1) 247S-257S
Gibbs M, Jetha A, Mellor D, Hampton SM, (2006) Diurnal variation in glycaemic index, comparison of a low and high glycaemic index mixed meal. Proceedings of the Nutrition Society 65: 82A
Al-Naimi S, Hampton SM, Richard P, Tzung C, Morgan LM.(2004) Postprandial metabolic profiles following meals and snacks eaten during simulated night and day shift work Chronobiol Int 21 (6): 937-947
The time scale depends on how many food products are required to be tested. One food product takes approximately three weeks from receiving the food/beverage but we can reduce that time if the food product results are required faster. If large numbers of food products are GI tested then we will report results every five products. This will take approximately 8 weeks from receiving the food/beverage.
If other analysis is required this may result in a longer time scale.
Results are reported to the client as soon as they are available we will keep the client informed of progress on a regular basis. For large numbers of foods/beverages the client will be informed when every five products are tested.
Results are reported as GI value plus a graph of the glucose (insulin) postprandial responses. This will show how quickly the glucose levels rises and how long glucose levels remain elevated.
Contact Dr S Hampton for any more information 01483 689732 or e-mail firstname.lastname@example.org
What is the difference between glycemic index (GI) and glycemic load (GL)?
Your blood glucose rises and falls when you eat a meal containing carbohydrate. How high it rises and how long it remains high depends on the type of the carbohydrate and the quantity you consume being the major factors. However there are factors which have a role . Glycaemic load or GL combines both the quality and quantity of carbohydrate in one 'number'. It's the best way to predict blood glucose values of different types and amounts of food. The formula is:
GL = (GI x the amount of carbohydrate) divided by 100.
Let's take a single apple as an example. It has a GI of 40 and it contains 15 grams of carbohydrate.
GL = 40 x 15/100 = 6 g
What about a small baked potato? Its GI is 80 and it contains 15 g of carbohydrate.
GL = 80 x 15/100 = 12 g
So we can predict that our potato will have twice the metabolic effect of an apple. You can think of GL as the amount of carbohydrate in a food 'adjusted' for its glycaemic potency.
How much food is required to measure GI values?
This will depend on the amount of available carbohydrate present in the food product that is being tested.
3 Delivery of products?
The product delivery need to be discussed with the team.