Even minimal polishing of an Indian parboiled brown rice variety leads to increased glycemic responses.

BACKGROUND AND OBJECTIVES: To evaluate the effect of polishing on the glycemic properties of Indian parboiled brown rice.

METHODS AND STUDY DESIGN: We evaluated the effect of different degrees of polishing on the glycemic and insulinemic responses of Bapatla (BPT-5204), Indian parboiled Indica rice variety. Brown rice (BR), under milled rice (UMR) and white rice (WR) with 2.3% and 9.7% degree of polishing (DOP), respectively, were prepared and evaluated for the glycemic properties. Incremental Area Under the Curves (IAUC) were estimated for both glycemic index (GI) in 12 healthy participants (6 men, 6 women) and 24 hr glycemic response studies in 13 overweight participants (5 men, 8 women) using continuous glucose monitoring (CGM) system with ≈2000 kcal/day rice diets. Differences in pre and post meal insulin (Δ) were assessed.

RESULTS: The GI of WR (GI=79.6) and UMR (GI=73) were significantly higher than BR (GI=57.6) (p<0.01). Similar results were obtained for 24 hr glycemic responses [IAUC: WR=58.4, UMR=55.5, BR=34.7 mg*5 min/dL, respectively]. The Δ Insulin responses were lower with BR meals compared with UMR and WR (p=0.025; p=0.003).

CONCLUSIONS: Both UMR and WR had a high GI while BR had a medium GI. This could have influenced the 24 h glycaemic and insulinemic responses of BR which had the lowest responses as compared with UMR and WR, and the latter two had similar higher responses. Thus any degree of polishing leads to higher glycaemic responses.