RESISTANT STARCH AS ENERGY

Objective: This study was designed to compare the metabolizable energy of two starch sources, standard cornstarch and high amylose cornstarc h. Methods: Diets containing 70% amylose (AM) or 70% amylopectin (AP) cornstarches were fed to 10 control and 14 hyperinsulinemic men for 14 weeks. During the last 4 weeks of each period, subjects were fed a co ntrolled diet containing 34% of total energy from fat, 15% from protei n and 51% from carbohydrate (55% of carbohydrate provided AM or AP). D uplicate food and all urine and feces were collected during the second week of the controlled diets for energy, nitrogen, fiber and starch d eterminations. Metabolizable energy (ME) was calculated as [energy int ake minus (fecal plus urinary energy excretion)]. Results: Total fiber uncorrected for resistant starch was 35.2 g and 48.8 g in the AP and AM diets, respectively. The AM dirt contained an average of 29.7 g res istant starch (16% of total starch) while the AP diet averaged 0.8 g ( less than 0.01%). ME was not significantly different between the AM an d AP diets nor between the control and hyperinsulinemic subjects. Feca l energy and nitrogen was significantly higher after the AM compared t o AP diet. Based on energy intake and fecal excretion from ail subject s, the partial digestible energy value for the resistant starch averag ed 11.7 kJ/g resistant starch which was 67.3% of the energy of standar d cornstarch. Control and hyperinsulinemic subjects differed in their ability,ru digest resistant starch, averaging 81.8% anti 53.2%, respec tively. The hyperinsulinemic, but not control, subjects had significan tly higher breath hydrogen expirations (LS means, p > 0.05) in the fas ting, 1-5 hour and 7 hour collections alter consuming the AM when comp ared to the AP tolerance meal. Conclusions: The type of starch consume d in the diet did not statistically affect metabolizable energy, Based on ME and breath hydrogen expiration, amylose and the resistant starc h from amylase appears to be utilized as an energy source. Resistant s tarch averaged 2.8 kcal/g for all 24 subjects but only 2.2 kcal/g in t he hyperinsulinemic subjects.