CONTRIBUTION OF FIBER AND RESISTANT STARCH TO METABOLIZABLE ENERGY

Recommendations made to increase complex carbohydrate and fiber intake in the United States may result in energy loss from increased fecal l osses of starch, protein, and fat. The type of fiber or starch and the amount consumed affect digestion of the carbohydrate and interactions with other nutrients. On average, 8.4 kJ (2 kcal) digestible energy/g is available from up to 70 g poorly digested carbohydrate/d. Undigest ed fiber and starch are important substrates for colon bacteria and ar e fermented to short-chain fatty acids, hydrogen, and methane. Hydroge n and methane excreted through the lungs have been used as indicators of colonic fermentation. Fermentation appears to contribute significan t digestible energy when > 20 g poorly digested carbohydrate/d is cons umed.