Abstract
Plasma zinc concentrations (PZC) have been shown to significantly increase during zinc supplementation. This study investigated the effects of daily preventive zinc supplementation on hair and nail zinc concentrations compared with a control group. In a randomized controlled trial, 6- to 23-month-old children (n = 3407) in Lao PDR were randomly assigned to one of four groups and followed for ~ 36 weeks: daily preventive zinc dispersible tablet (7 mg/d; PZ), daily micronutrient powder (10 mg zinc/d; MNP), therapeutic zinc supplements for diarrhea treatment (20 mg/d for 10 days; TZ), or daily placebo powder (Control). Plasma, hair, and nail zinc concentrations were assessed in a sub-sample of participants (n = 457) at baseline and endline. At baseline, 75% of children had low PZC (< 65 μg/dL). At endline, geometric mean (95% CI) PZC were greater in the PZ and MNP groups compared with the TZ and control groups (P < 0.01), but hair zinc concentrations did not differ among groups (P = 0.99). Nail zinc concentrations were marginally higher in the PZ (115.8 (111.6, 119.9) μg/g) and the MNP (117.8 (113.3, 122.3) μg/g) groups than in the TZ group (110.4 (106.0, 114.8) μg/g; P = 0.055) at endline. This study does not support the use of hair zinc as a biomarker of zinc exposure in young children. However, it provides some evidence that zinc concentrations in nails may respond to supplemental zinc interventions and supports the need for collecting additional data on this emerging biomarker.
Highlights
Zinc is an essential micronutrient for human health, and infants and young children in low- and middle-income countries are at high risk of zinc deficiency [1, 2]
Recent recommendations from the Biomarkers of Nutrition for Development (BOND) zinc expert panel, the WHO, UNICEF, International Atomic Energy Agency (IAEA), the International Zinc Nutrition Consultative Group (IZiNCG), and the EURopean micronutrient RECommendations Aligned (EURRECA) Network of Excellence [5,6,7] have concluded that plasma zinc concentration is the only valid biochemical indicator currently available to assess the risk of zinc deficiency in populations and measure population-level exposure to zinc supplementation
To help fill the first of the aforementioned data gaps, the primary objective of the present study was to investigate the effects of daily preventive zinc supplementation, provided either as dispersible zinc tablets or low-iron high-zinc containing multiple micronutrient powders (MNP), on changes in hair and nail zinc concentrations compared with a control group
Summary
Zinc is an essential micronutrient for human health, and infants and young children in low- and middle-income countries are at high risk of zinc deficiency [1, 2]. Preventive zinc supplementation has been shown to decrease morbidity from diarrhea and acute lower respiratory infections, reduce all-cause mortality, and increase linear growth and weight gain among infants and young children in vulnerable populations [3]. Therapeutic zinc supplementation administered during episodes of diarrhea has been shown to reduce the duration of diarrheal illness [4]. The measurement of plasma zinc concentration requires invasive blood collection, biohazardous materials, complex preparation, and consideration of downstream processes like transportation and storage of samples, including cold chain control [9]
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