Interaction between zinc and iron in rats - Experimental results and mathematical analysis of blood parameters

The importance of interactive effects, of minerals in general, on nutrient requirements is becoming increasingly recognized. The interaction between i ron and zinc has not been as widely investigated. The metabolic interrelati onships between dietary iron and zinc have been known for years, but some s ubtle relationships may have gone unrecognized. Because nutrient interactio ns are not necessarily linear in nature, it may be inadequate to apply line ar statistical models to study the interaction between zinc and iron. In th is study, we used traditional as well as a nonlinear approach in analyzing experimental results from groups of rats fed a wide range of dietary zinc a nd iron. Male weanling Sprague-Dawley rats were used in a 5 x 4 factorially arranged experiment. Dietary variables were iron (as ferric citrate) at 4, 12, 24, 48, or 96 mug Fe/g diet and zinc (as zinc carbonate) at 5, 10, 20, or 40 mug Zn/g diet. After 7 wk, hematological parameters were measured an d plasma ceruloplasmin and cholesterol were determined. In addition to inte ractive effects as shown by analysis of variance, the application of log-li near analysis to the experimental data revealed a far broader range of inte ractions between dietary iron and zinc. As a result of our experiment and i ts quantitative analysis, we conclude that the interaction between iron and zinc is nutritionally important and that dietary iron affected the respons e of many blood parameters to dietary zinc. The complete dataset can be fou nd at http://www.gfhnrc.ars.usda.gov/fezn.