THE EFFECT OF RAW POTATO STARCH ON ENERGY-EXPENDITURE AND SUBSTRATE OXIDATION

Because resistant starch (RS) is not absorbed as glucose in the small intestine of healthy humans, postprandial thermogenesis should be lowe r after the intake of RS as compared with digestible starch. To evalua te this hypothesis, we measured 5-h postprandial thermogenesis and sub strate oxidation by indirect calorimetry after ingestion of 50 g prege latinized (0% RS) and 50 g raw potato starch (54% type II RS) in 15 he althy, normal-weight young males. The subjects consumed each starch (m ixed in diluted fruit syrup) twice on separate days and in random orde r. RS intake was followed by lower thermogenesis (46.5 +/- 13.1 compar ed with 115.4 +/- 10.4 kJ/5 h; P = 0.008), lower glucose oxidation (P < 0.0005), and greater fat oxidation (P = 0.013) than was pregelatiniz ed starch consumption. Our results suggest that RS has no thermogenic effect and that its presence does not influence the size of the thermi c response to digestible starch.