Glycemic responses to glucose and rice in people of Chinese and European ethnicity

The Glycaemic Index (GI) provides a measure of a person’s rise in blood glucose following consumption of a test food relative to a reference food. Data from some observational studies suggest that consuming high GI food is a risk factor for obesity and type II diabetes. Although more than 60% of the world’s population with diabetes will come from Asia, studies of GI in Asian people are scarce. White rice is a staple food in Asia and a major determinant of GI in the Asian diet. In the clinical setting in New Zealand, dietitians recommend patients consume varieties of rice shown to have a low GI value. However, published GI values are largely obtained in other countries using non-Asian test subjects. The relevance of GI values determined in Caucasian people for Asian consumers is questionable because we have found ethnic differences in GI. The rice varieties to be tested are generally available in New Zealand supermarkets and are jasmine, parboiled, basmati, brown and Doongara. The sucrose is LoGiCane sugar. Testing will be undertaken over a period of 6 weeks. Test days will be non-consecutive and be undertaken 2 to 3 days per week. The trial is measuring the acute response of blood glucose immediately following a test meal served in portions containing 50g available carbohydrate. Equal numbers of male and female volunteers will be enrolled within age brackets (10 aged 18-30y, 10 aged 31-40y, and 10 aged 41-50y) for each ethnicity. The foods will be tested in sequence but the entry point of a participant into that sequence will be randomized. As such, ethnic-specific diet plans are not required although there are recommendations regarding standardisation of evening meals and exercise prior to each test day and exercise on the morning of the test day. Postprandial glycaemia will be measured using capillary blood and a Hemocue instrument. Extent of chewing will be determined by having the participants chew and expectorate a weighed sample and then rinsing over a laboratory sieve in order to measure the proportion of finely chewed rice. Saliva samples will be collected for the determination os salivary alpha-amylase activity using a proprietary kit.