A transgressive brown rice mediates favourable glycaemic and insulin responses

BACKGROUND: We evaluated glycaemic response of a brown rice variant (BR) developed by cross-breeding. Subjects (n = 9) consumed 50 g carbohydrate equivalents of BR, white rice (WR) and the polished brown rice (PR) in comparison to 50 g glucose reference (GLU) in a cross-over design. Plasma glucose and insulin at 0, 15, 45, 60, 90, 120 and 180 min were measured and incremental area under the curve (IAUC) and indices for glucose (GI) and insulin (II) calculated.
RESULTS: BR compared to PR or WR produced the lowest postprandial glycaemia (GI: 51 vs 79 vs 86) and insulinaemia (II: 39 vs 63 vs 68) irrespective of amylose content (19 vs 23 vs 26.5%). Only BR was significantly different from GLU for both plasma glucose (P = 0.012) and insulin (P = 0.013) as well as IAUC(glu) (P = 0.045) and IAUC(ins) (P = 0.031). Glycaemic and insulinaemic responses correlated positively (r = 0.550, P < 0.001). Linear trends for IAUC(glu) and IAUC(ins) indicated a greater secretion of insulin tied in with a greater glycaemic response for WR (r(2) = 0.848), moderate for PR (r(2) = 0.302) and weakest for BR (r(2) = 0.122).
CONCLUSION: The brown rice variant had the lowest GI and II values but these advantages were lost with polishing.