Bioavailability of copper in isolated soybean protein using the rat as an experimental model

The bioavailability of copper from isolated soybean protein was evaluated with growing rats. Copper depletion and repletion feeding techniques were used to evaluate the biologically available copper. Serum and liver copper contents were used as physiological indication to determine the bioavailability of copper in the diet. Sprague-Dawley male weanling rats were fed a diet low in copper for 21-42 days and then transferred to the test diets containing different levels of copper from copper carbonate or isolated soybean proteins for 7-14 days. Statistical analyses of serum and liver copper by using the slope-ratio bioassay were performed to determine the relative potency of the test products to the copper carbonate standard. The results from four feeding experiments indicate that 1) hypocupremia was produced by feeding a low copper basal diet to weanling rats after 28 days, 2) the time required to replete serum and liver copper was 7 days and 3) copper was available equally from isolated soybean protein and copper carbonate.