Effect of gamma irradiation on the 24-h glycemic responses of parboiled brown rice diets in Asian Indian adults: A randomized cross-over study

Background: The nutritional importance of brown rice (BR) is well established. Despite several nutritional benefits of BR, its consumption remains limited due to long cooking time and limited shelf-life. BR can be subjected to processing to improve shelf-life. Gamma irradiation is one such strategy, but it could induce changes in the grain and thus affect its glycemic properties. Aims and objectives: The aim of this study was to look at the 24-h glycemic response of irradiated and non-irradiated BR-based iso-caloric diets in Asian Indians. Methods: Fifteen (mean body mass index: 24 ± 2.6 kg/m2) Asian Indian adults without diabetes, aged 25–39 years, participated in this randomized cross-over study. Iso-caloric diets were prepared with two varieties (ADT 43 and Swarna) of parboiled gamma-irradiated brown rice with 750–820 Gy dosage (IBR) and non-irradiated brown rice (NIBR). After the participants consumed these diets, 24-h glycemic responses were recorded using a continuous glucose monitoring system. The mean positive change from baseline glucose concentration was calculated as the incremental area under the curve (IAUC) for both the diets. Results: The percentage difference in 24-h average IAUC was 10% lower in the IBR diets when compared with NIBR diets, irrespective of the variety of BR (P = 0.56). In the case of ADT 43 rice variety, both IBR and NIBR diets showed similar IAUC (P = 0.68). However, the IBR of Swarna rice variety showed 21% lower IAUC when compared with the NIBR diet (P = 0.21). Comparing the IBR varieties, Swarna showed 21% lower IAUC than ADT 43 (P = 0.21), whereas between NIBR varieties, only 0.79% difference was observed between ADT 43 and Swarna (P = 0.93). Conclusions: Gamma irradiation of parboiled BR did not produce significant differences in the 24-h glycemic responses for BR-based diets. Swarna variety was better than ADT 43 with regard to glycemic response. Judicious application of radiation technology to BR varieties may help in shelf-life extension without affecting the glycemic properties.