Glycaemic Index of Foods in Healthy Volunteers

Overview

The objective of this study is to assess the effect that dietary carbohydrates have on blood sugar by measuring the glycaemic index. The glycaemic index is a comparison between the effect of equal amounts of carbohydrate from a test food compared to a standard (in this case glucose) on blood sugar. Different foods that contain different carbohydrates have different effects on blood sugars. This is of interest as a number of studies have shown that the level of sugar in the blood after a meal relates directly to the risk of developing heart disease and diabetes. The aim of collecting this data is to be able to give advice to people about the carbohydrates they eat to reduce the risk of diabetes and heart disease.

The study is a randomized cross-over controlled trial: the order of the test foods will be randomized by an independent internet-based program; each participant will be asked to consume all the products; the test food will be compared with a control (in this case 50g glucose). Suitable subjects will be invited for a screening visit to check for eligibility criteria. Body weight and height measurements will be taken as well as a standard biochemical and haematological screen. If they are eligible and willing to take part, volunteers will be entered into a database and contacted when a GI test becomes available. Volunteers may take part in more than one GI testing up to a maximum of 40 visits per year. Volunteers may withdraw from the database or the study at any time without giving any reason. Subjects will be asked to come for a set amount of visits for each GI test depending on the number of product that need to be tested (minimum 3 maximum 12 visits for each testing). The volunteers will be informed of the number of visits before they enter the GI testing. For each visit, subjects are tested in the morning after a 10-12h overnight fast. Three fasting blood samples are taken (-5, -3, -1) 2 minutes apart after which subjects consume the test meal or reference food at an even rate over 15 min. All subjects are asked to record the time it takes in minutes to consume the test food/reference. Further blood samples are taken at 15, 30, 31, 32, 45, 60, 90 and 120 min after the beginning of the meal. The test meal and reference food should be consumed with a 250ml drink of water. This remains constant for each of the tests in the series. Blood is obtained by finger-pricking using disposable Unistix needles. In previous studies, capillary blood has yielded less between-subject variation in GI. Instant glucose analysers will be used.