Cross-linked phosphorylated RS4 wheat starch reduces glucose and insulin responses after 3 days of pre-feeding in healthy adults: an acute, double-blind, randomized controlled clinical trial.

When this project was designed, there was no evidence that adding resistant starch to available carbohydrate (avCHO) reduced glycaemic and insulinaemic responses (GIR). We compared GIR elicited by a cookie containing cross-linked phosphorylated RS4 wheat starch (Fibersym®) (RS4) versus an avCHO-matched control-cookie (CC) after  = 15 adults had consumed RS4 or CC daily for 3-days using a double-blind, randomised, cross-over design. The difference in glucose iAUC over 0-2 h (primary endpoint) (mmol × min/L) after RS4, (mean ± SEM) 106 ± 16, versus CC, 124 ± 16, was not significant ( = 0.087). However, RS4 reduced 0-90 min glucose iAUC (72 ± 9 vs 87 ± 9,  = 0.022), peak glucose concentration (6.05 ± 0.36 vs 6.57 ± 0.31 mmol/L,  = 0.017) and 0-2 h insulin iAUC (189 ± 21 vs 246 ± 24 nmol × h/L,  = 0.020). These results show that RS4 reduced postprandial glycaemic and insulinaemic responses when added to avCHO, but do not prove that the products of its colonic fermentation are required for this effect.