Effect of zinc protoporphyrin IX on dietary zinc bioavailability

Dietary zinc availability of zinc protoporphyrin IX (ZnPP), which mainly contributes to the color of dry-cured meat products, was examined in rats fed a low-zinc diet (5ppm Zn). Reagent ZnPP (5R) and ZnPP formed in the liver (5L) were used as dietary zinc sources of ZnPP, and zinc sulfate (5S) was used as a dietary inorganic zinc source. Body weight gains in the 5L and 5R groups were significantly lower than those in the 5S group and zinc-sufficiency group (20S ; 20ppm zinc by using zinc sulfate) and were comparable to that in the zinc-deficiency (ZD) group. There were no significant differences in zinc contents in the liver, thymus, skeletal muscle and hair among the groups. However, in the serum, testis, kidney, bone and skin, zinc contents in the 5L and 5R groups were significantly lower or tended to be lower than those in the 20S and 5S groups. Serum alkaline phosphatase activities in the 5L and 5R groups were significantly lower than those in the 20S and 5S groups and were comparable to that in the ZD group. Although there were significant differences in manganese contents in the serum and some tissues, the other mineral contents were not affected by zinc sources or the zinc level. The results suggest that the dietary zinc availability of ZnPP is not higher than that of inorganic zinc.