Serum zinc reference intervals and its relationship with dietary, functional, and biochemical indicators in 6- to 9-year-old healthy children

BACKGROUND: Zinc is an important cause of morbidity, particularly among young children. The dietary, functional, and biochemical indicators should be used to assess zinc status and to indicate the need for zinc interventions. OBJECTIVE: The purpose of this study was to determine the zinc status and reference intervals for serum zinc concentration considering dietary, functional, and biochemical indicators in apparently healthy children in the Northeast Region of Brazil. DESIGN: The cross-sectional study included 131 healthy children: 72 girls and 59 boys, aged between 6 and 9 years. Anthropometric assessment was made by body mass index (BMI) and age; dietary assessment by prospective 3-day food register, and an evaluation of total proteins was performed. Zinc in the serum samples was analyzed in triplicate in the same assay flame, using atomic absorption spectrophotometry. RESULTS: With respect to dietary assessment, only the intake of fiber and calcium was below the recommendations by age and gender. All subjects were eutrophic according to BMI and age classification. Zinc intake correlated with energy (p=0.0019), protein (p=0.0054), fat (p<0.0001), carbohydrate (p=0.0305), fiber (p=0.0465), calcium (p=0.0006), and iron (p=0.0003) intakes. Serum zinc correlated with protein intake (p=0.0145) and serum albumin (p=0.0141), globulin (p=0.0041), and albumin/globulin ratio (p=0.0043). Biochemical parameters were all within the normal reference range. Reference intervals for basal serum zinc concentration were 0.70–1.14 µg/mL in boys, 0.73–1.17 µg/mL in girls, and 0.72–1.15 µg/mL in the total population. CONCLUSIONS: This study presents pediatric reference intervals for serum zinc concentration, considering dietary, functional, and biochemical indicators, which are useful to establish the zinc status in specific groups. In this regard, there are few studies in the literature conducted under these conditions, which make it an innovative methodology.