Effect of zinc supplementation on respiratory tract infections in children with cystic fibrosis.

Zinc (Zn) has significant anti-oxidant and anti-inflammatory activity. Zn deficiency can occur in subsets of patients with cystic fibrosis (CF) especially those with malabsorption and impaired growth. Although supplemental Zn has significantly reduced infections in various disorders, its efficacy has not been thoroughly investigated in CF. We performed a double blind placebo controlled pilot study to investigate the effect of daily 30 mg elemental Zn for 1 year on the rate of respiratory tract infections (RTIs), use of antibiotics and plasma cytokines in 26 children with CF (ages 7-18 years). Plasma Zn, Cu, inflammatory cytokines and ex vivo generation of IL-2 were measured at baseline and at the end of the study. The number of days of oral antibiotics was lower in Zn treated patients compared to placebo (P = 0.05). However, compared to placebo, the effect of Zn was greater in patients who exhibited low plasma Zn at baseline (P = 0.02) than those who had plasma Zn levels identical to normal subjects (P = 0.55). Zn supplementation was marginally effective in reducing percentage increase in plasma IL-6 and IL-8 while increasing the percentage change in ex vivo generation of IL-2 in isolated mononuclear cell. In conclusion, oral intake of 30 mg/day of Zn reduced the number of days of oral antibiotics used to treat RTIs in children with CF. A higher daily Zn dose may be needed to decrease RTIs and modify immune responses.