Background and objectives: Vitamin A and zinc are interrelated, but the effects of zinc on vitamin A supplementation on morbidity are inconsistent and not well understood. We investigated the effects of zinc and vitamin A supplementation on immune responses in Indonesian pre-schoolers.
Methods and study design: In a twostage study design, 826 children (2-5year old) were randomly assigned to receive daily zinc supplement (10 mg) or placebo for 4 months. At 2 months, both groups received a 200,000 IU vitamin A capsules through national vitamin A program. Data were collected at baseline, two and four months, resulting in 4 groups for comparisons: - no zinc no vitamin A (Placebo), zinc only, vitamin A only, and zinc plus vitamin A. Hair, blood and saliva samples were collected to measure hair zinc and serum retinol (vitamin A) concentration, ex-vivo IFN-γ, serum IgG and salivary IgA from 81 children selected randomly from each group.
Results: At baseline, there were no differences between treatment groups. Zinc supplementation increased ex-vivo IFN-γ production, greatest amongst boys, younger (<3.5 years), normal weight and children with low baseline retinol concentration. Vitamin A supplementation increased IFN-γ only in those with low baseline retinol, with no effect on serum IgG and salivary IgA. After vitamin A supplementation, zinc had an effect on salivary IgA among younger and underweight children.
Conclusions: Zinc supplementation increased IFN-γ (cellular immune responses) and modified the effect of vitamin A supplementation on salivary IgA (mucosal innate immune response) in younger and underweight children.