Digestibility of carbohydrate foods in an ileostomate: relationship to dietary fiber, in vitro digestibility, and glycemic response.

The aim of this study was to assess differences between starchy foods in the amount of carbohydrate which escapes small intestinal absorption. One ileostomate volunteer tested in metabolic feeding trials a total of 20 starchy foods (nine of which were repeated on two to seven occasions, mean 3.5 +/- 1.7). This ileostomate volunteer exhibited macronutrient and fiber losses that were within 97.3 +/- 6.6% of the mean, for a range of foods eaten by three other ileostomates and was therefore believed to be representative. Measurement of available carbohydrate in ileal effluent demonstrated a wide range of recoveries from 2.7 to 18% from different starchy foods. The available carbohydrate losses related to the fiber content (r = 0.885, p less than 0.001), in vitro digestibility of the food (r = -0.867, p less than 0.01), and their glycemic responses (r = -0.611, p less than 0.05). Our data support the concept that available carbohydrate losses to the colon may be greater in many foods than the carbohydrate entering the colon as dietary fiber. The food factors responsible are diverse and the possible metabolic consequences of carbohydrate malabsorption may be broad.