Effects of Type 2 Resistant Starch Consumption on Insulin Sensitivity in Men and Women

This study evaluated the effects of two levels of intake of a natural type 2 resistant starch (RS; Hi‐maize 260, National Starch, LLC) on insulin sensitivity in subjects with waist circumference ≥89 cm (women) or ≥102 (men). Participants received 0 (control starch), 15 or 30 g/d (double‐blind) of RS in random order for 4‐wk periods, separated by 3‐wk washouts. Insulin sensitivity index (SI) was assessed at the end of each period using the insulin‐modified intravenous glucose tolerance test (minimal model). The efficacy evaluable sample included 11 men, 11 post‐ and 10 pre‐menopausal women with mean±SEM age 49.5±1.6 y, body mass index 30.6±0.5 kg/m2 and waist 105.3±1.3 cm. The analysis showed a significant treatment main effect (p=0.008) and a treatment by sex category interaction (p=0.05). Median SI during control was 3.14 × 10‐4 × min‐1 × (μU/mL)‐1. Median changes compared to control during the 15 g/d RS condition were 42.1%, 18.4%, and −0.4% in men, postmenopausal and premenopausal women, respectively. Corresponding changes during the 30 g/d RS condition were 59.8%, 7.3%, and −3.1%. Responses in premenopausal women may have been confounded by changes in insulin sensitivity during the menstrual cycle. These results suggest that consumption of 15–30 g/d of RS increases insulin sensitivity and that future studies in premenopausal women should control for menstrual cycle phase.