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Enhancement of Cu Bioavailability in the Rat by Phytic Acid^1,2,

Department of Food Science and Nutrition, University of Missouri, Columbia, MO 65211

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 (<1.0 µg/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 µg Cu/g (CuCO₃) and 0, 0.4 or 0.8% phytic acid as sodium phytate at each Cu level. All diets contained 30 µg 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 µg 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.

KEY WORDS: • copper bioavailability • phytic acid • serum copper • liver copper • liver superoxide dismutase • ceruloplasmin

¹ This work was supported by the Agricultural Experiment Station, University of Missouri, Columbia. Contribution from the University of Missouri Experiment Station, Journal Series No. 9775.

² Presented in part at the meeting of the American Institute of Nutrition, St. Louis, MO, April, 1984 [Lee, D.-Y., Schroeder, J., III & Gordon, D. T. (1984) The effect of phytic acid on copper bioavailability. Fed. Proc. 43: 616 (abs.)].

³ Present address: USDA RS, Human Nutrition Research Center, University Station, Grand Forks, ND 58202.

⁴ Present address: Food Science and Human Nutrition Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.

⁵ To whom correspondence should be addressed.

Manuscript received 13 August 1987. Revision accepted 20 January 1988.