Enhancement of Cu bioavailability in the rat by phytic acid

The objective of this study was to evaluate the effect of phytic acid on copper (Cu) bioavailability. Male weanling rats were fed a Cu-deficient diet (less than 1.0 micrograms/g) for 4 wk and then were divided into 12 groups (n = 8) in a factorial design. Cu-deficient rats were then fed diets containing 1.4, 3.0, 5.2 or 10.5 micrograms Cu/g (CuCO3) and 0, 0.4 or 0.8% phytic acid as sodium phytate at each Cu level. All diets contained 30 micrograms Zn/g. After 3 d of Cu repletion, liver copper (LCu), liver Cu-Zn superoxide dismutase (LSOD) activity, serum Cu (SCu) and serum ceruloplasmin (CP) concentrations were determined. These parameters were used as indexes of Cu bioavailability. The addition of phytic acid to diets fed to Cu-deficient rats significantly enhanced Cu bioavailability compared to that of rats fed diets without phytic acid. Coefficients of determination (r2) were calculated for each response parameter versus dietary Cu concentration. The r2-values for pooled LCu and LSOD values were 0.31 and 0.30, respectively, between 1.4 and 5.2 micrograms Cu/g. At low dietary Cu concentrations, liver Cu parameters (i.e., LCu and LSOD) were more responsive indexes of Cu status than SCu and CP. Each index of Cu status was found to correlate with the other indexes of Cu nutriture. Phytic acid is postulated to enhance Cu utilization by its ability to bind other dietary components, such as Zn, that compete with Cu at the site of intestinal absorption.