Iron and zinc supplementation improves indicators of vitamin A status of Mexican preschoolers.
Level 2 - randomized trial
Individual double-blind randomized controlled trial
PubMed 10702174 · doi:10.1093/ajcn/71.3.789
What was done
Researchers conducted a 6-month, double-blind, placebo-controlled trial in 219 rural Mexican children aged 18 to 36 months. Participants were randomly assigned to one of four daily intervention groups: 20 mg zinc, 20 mg iron, 20 mg zinc plus 20 mg iron, or a placebo. Outcomes measured were plasma retinol, retinol binding protein (RBP), and transthyretin.
What was found
The abstract does not report exact numerical values, standard deviations, or effect sizes. Directionally, plasma retinol increased across all three supplemented groups compared to placebo after 6 months. Zinc alone significantly increased plasma retinol and transthyretin, but the change in RBP was not statistically significant. Iron alone significantly increased plasma retinol, RBP, and transthyretin. Combined zinc and iron supplementation significantly increased plasma retinol, but did not significantly alter RBP or transthyretin. Children deficient in zinc, iron, or vitamin A at baseline showed a significantly greater increase in retinol than children with adequate baseline status.
Why it matters
This study shows that correcting iron or zinc deficiencies can improve circulating vitamin A markers without adding vitamin A, supporting the existence of metabolic interactions between iron, zinc, and vitamin A transport proteins.
Limits
The abstract reports no numerical values, confidence intervals, or p-values. Findings are restricted to rural Mexican preschoolers aged 18 to 36 months and may not generalize to populations with different nutritional baselines. Functional health outcomes beyond plasma biomarkers were not evaluated.
Cited by
- supports Vitamin A will not work effectively in the body if a person is deficient in zinc.