Metabolizable Energy of Diets Low or High in Dietary Fiber from Cereals when Eaten by Humans

Abstract

The metabolizable energy (ME) of two diets that differed in their content of dietary fiber (DF) from cereal products was measured in balance experiments in six human subjects. DF intake was 19.7 g/d with the low fiber diet and 48.3 g/d with the high fiber diet. Daily gross energy intakes were 2114 kcal (8845 kJ) and 2341 kcal (9795 kJ)/d with the low and the high fiber diets, respectively. DF contributed 83 kcal (347 kJ) and 203 kcal (849 kJ) to daily gross energy intake with the low and the high fiber diets, respectively, when heat of combustion of DF of 4.2 kcal (17.6 kJ)/g was assumed. Increasing the intake of DF resulted in an increase in stool weight and a greater fecal energy loss. Total energy losses were 253 kcal (1056 kJ) and 409 kcal (1711 kJ)/d with the low and the high fiber diets, respectively. ME provided by the low and the high fiber diet were 1861 kcal (7786 kJ) and 1932 kcal (8083 kJ)/d. The total increase in energy losses due to the increase in DF consumption exceeded the gross energy provided by additional DF. Compared with the low fiber diet, ME provided by protein and fat was decreased during the high fiber diet. Calculation of the apparent digestibility of DF indicated that fiber may have provided ME in the form of short-chain fatty acids during the low as well as during the high fiber intake. However, estimation of the amount of fecal gross energy indicated that available components of the diet, such as starch, must have been utilized incompletely during both experimental periods.