Dietary native resistant starch but not retrograded resistant starch raises magnesium and calcium absorption in rats

The effects on calcium and magnesium absorption of dietary native and retrograded cornstarch were studied in rats. Uncooked high amylose starch granules (35% of total glucose equivalents as enzyme-resistant starch) and cooked and cooled (-20 degrees C) high amylose starch (24% of total glucose equivalents as retrograded resistant starch) were used as test starches, and cooked normal starch (3% of total glucose equivalents as resistant starch) was used as control starch. Native vs. control starch raised the amount of polymerized glucose in ileum, but not in feces. Retrograded starch produced more polymerized glucose than control starch in both ileum and feces. When compared with control starch, ileal pH was significantly lowered by native starch and tended to be raised by retrograded starch. Cecal pH was lowered by the two preparations rich in resistant starch. Apparent absorption of calcium and magnesium was raised by native starch but not by retrograded resistant starch. Calcium concentrations in the liquid phase of the ileum tended to be elevated by native starch but were significantly lowered by retrograded starch relative to control starch. Magnesium and calcium concentrations in liquid cecal contents tended to be raised with native starch; they were unchanged with retrograded starch. It is suggested that native resistant starch raised calcium and magnesium absorption because it tended to enhance the solubility of these minerals in ileal and cecal digesta.