The resistant starch level of heat moisture-treated high amylose cornstarch is much lower when measured in the human terminal ileum than when estimated in vitro

Abstract

According to the definition of resistant starch (RS), the true value of foodstuff-derived RS can be assessed only from that found in the contents of the terminal ileum. To date, a few methods exist for in vivo measurement of RS in the terminal ileum, but their accuracy is questionable. The aim of this study was to quantify the level of RS in the terminal ileum to determine its true value as dietary fiber (DF). Volunteers (n = 7 men) were given a test meal containing 10 g of heat moisture-treated high amylose cornstarch (HMT-HAS) containing 8.8 g of RS as measured by Englyst's method. A double-lumen tube was positioned in the terminal ileum using the endoscopic retrograde bowel insertion method (ERBI). Intestinal contents were aspirated, and the amount of RS was measured as the glucose concentration (Englyst's method), and compared with the values for RS administrated orally using the same method. The mean amount of HMT-HAS-derived RS collected in the terminal ileum was 3.37 ± 0.95 g (mean ± SD), which was 34.5 ± 9.7% of the in vitro RS value. Furthermore, there were large individual differences in recoveries, ranging from 22.2 to 47.5%. The measured amount of HMT-HAS-derived RS was much smaller in our in vivo study than that measured in vitro, suggesting that in vitro measurement may inaccurately estimate the RS and DF levels of foodstuffs. The problem is further compounded by the large individual in vivo variations in RS values from subjects consuming identical diets.