Chitosan and resistant starch restore zinc bioavailability, suppressed by dietary phytate, through different mechanisms in marginally zinc-deficient rats

Abstract

The contribution of cecal fermentation of polysaccharides to the restoration of zinc bioavailability suppressed by phytic acid was assessed through the simultaneous evaluation of changes in zinc and magnesium absorption. Three weeks old rats were fed Fiber-free, 1% Chitosan, 2% Chitosan, 7% RS (raw potato starch), 14% RS, 2.5% Alginic acid or 5% Alginic acid diets, all containing phytic-acid, for three weeks. Feeding RS or chitosan significantly decreased cecal pH. Feeding chitosan decreased cecal SCFA, but increased cecal succinic acid concentration, while RS did not affect cecal SCFA, but increased succinic acid concentration. Cecal succinic acid concentration was strongly correlated with pH. Chitosan and RS restored zinc status; however, only RS increased magnesium absorption. RS restores zinc bioavailability by cecal fermentation, increasing SCFA and succinic acid concentrations, reducing cecal pH and probably increasing mineral solubility. The enhancement of zinc bioavailability by chitosan, however, appears to be related to its chelating properties. Abbreviations: CG, gas chromatography; GC-MS, gas chromatography–mass spectrometry; RS, resistant starch (from raw potato starch); SCFA, short chain fatty acids