Most studies indicate that 30% to 70% of RS is metabolized
(Ranhotra and others 1991a; Behall and Howe 1995; Behall and
Howe 1996; Cummings and others 1996; Ranhotra and others
1996), while the balance is excreted in the feces. The variability is largely due to effects caused by the malabsorption of the ingested
starch. In human subjects, replacement of 27 g of digestible starch
by RS (raw potato starch) in a single meal lowered diet-induced
thermogenesis by an average of 90 KJ/5 h (Heijnen and others
1995). A study was designed to compare the metabolizable energy
of 2 starch sources, standard cornstarch and high amylose
cornstarch (Behall and Howe 1996). Based on energy intake and
fecal excretion from all subjects, the partial digestible energy value
for the RS averaged 11.7 KJ/g RS, which was 67.3% of the energy
of standard cornstarch. Control and hyperinsulinemic subjects
differed in their ability to digest RS, averaging 81.8% and 53.2%,
respectively. RS averaged 2.8 kcal/g for all subjects but only 2.2
kcal/g in the hyperinsulinemic subjects. This enables the use of RS
in reducing the energy value of foods.