Quantifying resistant starch using novel, in vivo methodology and the energetic utilization of fermented starch in pigs

Resistant starch (RS) is commonly defined as the amount of starch and products of starch degradation not absorbed in the small intestine in healthy individuals. The proportion of dietary starch escaping enzymatic digestion largely depends on the type of starch. Fermentation of RS is difficult to quantify and all methodologies suffer their own limitations. The objective of this study was to determine the fate of carbon from RS compared with that of enzymatically digestible starch in group-housed pigs and to use these data for improving the estimation of the energetic value of RS. The study focused on quantification of starch fermentation in vivo using a noninvasive technique and on subsequent measurement of the kinetics of starch utilization and energy balance using indirect calorimetry. For this purpose, 10 groups of 14 pigs were assigned to one of two dietary treatments comprising diets containing 45% of either pregelatinized (P) or retrograded (R) corn starch. In both diets, a contrast in natural ¹³C enrichment between the starch and nonstarch components of the diet was created to partition between enzymatic digestion and fermentation of the corn starch. Energy and protein retention were measured using indirect calorimetry after adapting the pigs to the diets for 3 wk.

Fecal ¹³C enrichment was higher in the R-fed pigs (P < 0.001) and 43% of the R resisted enzymatic digestion. Energy retained as protein was unaffected and energy retained as fat was 29% lower than in P-fed pigs (P < 0.01). Digestible energy intake, metabolizable energy intake, and energy retention were reduced (P < 0.05) in R-fed pigs compared with P-fed pigs by 92, 54, and 33 kJ/(kg^0.75 × d), respectively. Therefore, the energy values of fermented RS were 53, 73, and 83% of the digestible, metabolizable, and net energy values of enzymatically degradable starch, respectively.

Creating a contrast in natural ¹³C enrichment between starch and nonstarch dietary components provides a promising, noninvasive, in vivo method for estimating the proportion of dietary starch fermented in the gastrointestinal tract.

WJJ Gerrits, MW Bosch and JJGC van den Borne. Quantifying resistant starch using novel, in vivo methodology and the energetic utilization of fermented starch in pigs. 2012. The Journal of Nutrition, 142: 238-244.