A study of Hassawi rice (Oryza sativa L.) in terms of its carbohydrate hydrolysis (in vitro) and glycaemic and insulinaemic indices (in vivo).

Background/objectives: A high prevalence of Type 2 diabetes exists in Saudi Arabia. Epidemiological evidence suggests that low glycaemic index (GI) diets reduce diabetes risk. Yet, little is known about the GI of traditional Saudi Arabian staples such as Hassawi rice (HR). HR was evaluated in terms of its GI and insulinaemic index (II). Comparisons were made in vitro assessing glucose released enzymatically. A long-grain rice variety available in both United Kingdom and Saudi Arabia was studied as a comparison.
Subjects/methods: For GI and II measurements, HR, Uncle Ben's rice (UBR) and a standard glucose solution were consumed by healthy subjects (n=13) on seven randomised occasions. Capillary bloods were collected at specific times over 2 h after food intake. Food and Agriculture Organization/World Health Organization protocols were used to determine GI and II. For the in vitro studies, cooked rice was incubated with hydrolytic enzymes under standardised conditions. Samples were taken at t=20 and t=120  min and rapidly available glucose (RAG) and slowly available glucose (SAG) were computed.
Results: Values of RAG and SAG were lower for HR compared with their respective values for UBR (P<0.001 and P=0.011, respectively). However, no significant difference was observed for GI (P>0.05) despite a lower insulin response noted for HR (P=0.007).
Conclusions: HR had a similar GI to UBR, although a lower insulin response was evident. RAG and SAG values were different for the two rice varieties despite similar GI values. These differences may be important in terms of their metabolic impact and outcome on diabetes.