Effects of different proteins on the metabolism of Zn, Cu, Fe, and Mn in rats.

Many factors are known to influence trace element metabolism and one of them is dietary protein. The present study examines the effects of casein, soybean protein, and peanut protein on the metabolism of the Zn, Cu, Fe, and Mn in growing rats. The results showed that Zn, Fe, and Mn excretions in the feces of peanut protein-fed rats (PPFRs) were similar to that of casein-fed rats (CPFRs) (p > 0.05), whereas all of the Zn, Cu, Fe, and Mn excretions in the urine of PPFRs were significantly higher than that of CPFRs (p < 0.05), but its apparent absorption rate (AAR) of Cu, Fe and its apparent retention rate (ARR) of Cu were all higher than that of CPFRs (p < 0.05). Hepatic Zn content of soybean protein-fed rats (SPFRs) was higher than that of CPFRs and PPFRs (p < 0.05 respectively) and serum, renal, and femoral Cu contents of SPFRs were significantly lower; however, hepatic Cu, and renal Mn contents were significantly higher than that of CPFRs (p < 0.05, respectively); The hepatic Fe content of SPFRs was significantly higher than that of CPFRs and PPFRs (p < 0.01, respectively). To sum up, compared to casein, soybean protein might be a good dietary source to make up for Zn and Fe deficiency, and also peanut protein to make up for Cu and Fe deficiency.