EFFECT OF INFANT FORMULA ZINC AND IRON LEVEL ON ZINC-ABSORPTION, ZINCSTATUS, AND IMMUNE FUNCTION IN INFANT RHESUS-MONKEYS

To evaluate the effects of marginal zinc (Zn) deficiency on Zn absorpt ion and metabolism, three groups of infant rhesus monkeys (n = 4/group ) were fed from birth to 5 months of age either a regular infant formu la (5 mg Zn/L) or a low-Zn formula (1 mg Zn/L). Since iron (Fe) intake may affect Zn absorption, the low-Zn formula was given without (1 mg Fe/L) or with Fe fortification (12 mg/L). At monthly intervals, Zn abs orption and retention were assessed by gavage feeding with Zn-65 and w hole-body counting immediately after and on days 4, 7, and 11 after in tubation. Blood samples were drawn before dosing for analyses of vario us potential markers of Zn status. Infants fed low-Zn formula had slow er weight gain than controls; however, length growth was similar in al l groups. Zn-65 retention was considerably higher in both groups fed l ow-Zn formula (40%) than in the control group (20%), whereas plasma Zn levels were normal in all infants. Plasma metallothionein levels were generally very low and detectable in only 5 samples of 48; however, 4 of these were found in control infants. Neutrophil chemotaxis assesse d at the end of the study was impaired in low-Zn infants compared to c ontrols. In addition, low-Zn infants had increased levels of interleuk in-2 at the end of the study. No differences were seen between the gro ups in hemoglobin levels, total white blood cells/absolute neutrophil counts, or plasma activities of 5'-nucleotidase or angiotensin convert ing enzyme. In conclusion, marginal Zn intake in infant rhesus monkeys resulted in increased Zn retention, which was not enough to completel y compensate for the lower Zn intake. The higher level of iron fortifi cation studied did not affect Zn retention significantly.