The effect of oral zinc supplementation on plasma levels of vitamin A and retinol-binding protein in cystic fibrosis.

Oral zinc supplementation with 100 mg zinc sulfate over an 8-week period in 36 patients with cystic fibrosis and 17 siblings did not affect the vitamin A transport system, as evidenced by an absence of consistent and significant quantitative changes in plasma levels of vitamin A, retinol-binding protein, and zinc, nor did the exogenous zinc appear to stimulate growth or exert any clinical benefit to the cystic fibrosis patients. The lack of response to zinc supplementation might be explained by the fact that the group of cystic fibrosis subjects studied was fairly healthy in regard to clinical status and certain blood parameters, including zinc.