Resistant Starches (RS2 and RS3) have Variable Effects on Bone Mineral Status in Rats

Nondigestible oligosaccharides may increase mineral absorption by changing the intestinal environment. The effect of feeding a diet containing 5% resistant starch, RS2 (uncooked native) or RS3, (cooked and retrograded) on calcium absorption and bone mineral status was studied in growing male rats for 4 weeks. Almost 100g more feed was consumed with resistant starch compared to control in four weeks. Mineral status improved as determined by femur concentration, but not through absorption. Mineral content of femurs increased 12, 10 and 9% for Ca, Mg and Zn respectively, while Fe decreased 23% after feeding RS3, but not RS2, compared with the control group. There was no increase in the percent retention for any of the tested minerals. 45 Ca absorption capacity was not affected by either resistant starch. We conclude that resistant starches improve mineral status possibly through increased food consumption, but not through increased absorption efficiency.