Effect of a Low Protein Diet on Retention of an Oral Dose of 65Zn and on Tissue Concentrations of Zinc, Iron, and Copper in Rats

Abstract

To assess some effects of protein malnutrition on zinc metabolism, rats were fed diets containing either 5 or 15% casein and either 9 or 33 ppm of zinc. Rats fed the 5% protein diets retained less of a single oral dose of ⁶⁵Zn than did those fed the 15% protein diets at either zinc level. Similarly, rats fed the diets containing 33 ppm of zinc retained less ⁶⁵Zn than did those fed the 9 ppm zinc diets. The retention data could be described by a second-order exponential equation; the results of this analysis indicated that the low protein diet reduced absorption of orally administered ⁶⁵Zn and increased endogenous excretion of zinc. Rats fed the low protein diet also had decreased zinc concentrations in plasma, liver and small intestine. The results of these experiments indicate that one important consequence of protein depletion may be a secondary zinc deficiency.