Zinc homeostasis in 1–4 year olds consuming diets typical of US children

Abstract

Few data have evaluated Zn balance in young children after the first year of life. The objective of the present study was to study the relationships among Zn intake, absorption, endogenous faecal excretion, and retention in a group of healthy children. Thirty children, aged 15-48 months, were studied on a diet representative of their usual daily mineral intake. Zn absorption was assessed using a dual-tracer stable-isotope technique. Endogenous Zn faecal excretion and Cu absorption were determined in a subset of children. We found that Zn intake from the in-patient weighed dietary record (5·0 (SD 2·1) mg/d) was significantly greater than the current estimated average requirement (EAR; 2·5 mg/d; P,0·0001). Neither fractional Zn absorption, urinary Zn excretion, nor endogenous faecal Zn excretion was significantly related to Zn intake (r 2 ,0·1; P. 0·4, for all). Absolute Zn absorption was significantly related to Zn intake (r 2 0·696; P, 0·0001), as was Zn retention (r 2 0·506; P,0·0001). Cu absorption was relatively high (75·1 (SD 10·8) %) despite the high Zn intake. The EAR for Zn based on this dataset would appear to be between 4·2 and 4·7 mg/d to allow for a net average retention of 120 mg/d consistent with growth needs. We concluded that at relatively high Zn intakes there was little evidence of down regulation of absorption or up regulation of urinary or endogenous faecal Zn excretion across the intake range studied. Zn retention was positively correlated with intake. A Zn intake between 4·2 and 4·7 mg/d should meet the requirement for normal growth for this age group. Children: Copper absorption: Mineral homeostasis: Nutrient requirements: Zinc absorptionThe dietary recommendations for mineral intakes by the Institute of Medicine were revised in the late 1990s. Intake recommendations for Zn in children aged 1-4 years changed dramatically from an RDA of 10 mg/d in 1989 1 to an estimated average requirement (EAR) of 2·5 mg/d, and an RDA of 3 mg/d 2 . These were based on a factorial approach assuming obligatory urinary losses of 7·5 mg/kg per d, integumental losses of 6·5 mg/kg per d, endogenous faecal losses of 34 mg/ kg per d and a requirement for growth of 120 mg/d 2 . Most of these assumptions were based on data in older subjects, due to the lack of suitable data from young children 2 .The principal reason for the absence of data in this age group is the impracticality of prolonged dietary regulation and complete urine and faecal collections that are required for traditional balance studies, especially in active children who are often not toilet-trained. Studies in this age group are now more feasible with modern stable-isotope methods in which Zn absorption can be directly assessed with a single timed urine sample 3,4 . Thus, our goal in the present study was to utilize stable isotopes to evaluate the relationships among Zn intake, absorption, endogenous faecal excretion, and retention in healthy small children on diets common in the USA.Zn intakes in children 1 to 4 years in the USA (median intake 5·81 m...

Perturbed Zinc Homeostasis in Rural 3–5-y-Old Malawian Children Is Associated With Abnormalities in Intestinal Permeability Attributed to Tropical Enteropathy

“…Urine and fecal specimens for total zinc and isotopic zinc ratios were analyzed as previously described (3,6). Samples were first diluted with weak acid to obtain a consistent Zn signal intensity.…”

“…The dual zinc stable isotope test involves administration of different zinc stable isotopes orally and i.v. and has been used to quantify the primary parameters that determine zinc homeostasis (3). Measurements of total dietary absorbed zinc (TAZ), endogenous fecal zinc (EFZ), and net zinc retention (NZR) have been made using this technique (3)(4)(5)(6).…”

Scientific Opinion on Dietary Reference Values for zinc

“…The IOM (2001) used a figure of 0.30 for the FAZ for older infants and children based on the literature available at that time. The Panel considers that subsequent data (Manary et al, 2000;Griffin et al, 2004;Lopez de Romana et al, 2005;Mazariegos et al, 2006;Sheng et al, 2006;Griffin et al, 2007) provide no reason to modify this figure. As this figure is based on mixed diets that probably contain variable quantities of phytate, no adjustment for phytate intake has been made.…”

Zinc and copper requirements in preterm infants: An examination of the current literature

“…The increasing availability of stable isotope methods to study mineral absorption may have resulted in a decrease in interest in more time-consuming and difficult metabolic balance studies [16]. Although stable isotopes are powerful tools to understand mineral absorption in vulnerable populations [36], they have limitations in estimating nutrient requirements unless urinary and fecal losses are either well described or can be estimated [37].…”