Zinc status and vitamin A transport in cystic fibrosis.

Zinc status and the retinol transport system were examined in 18 retinol supplemented cystic fibrosis (CF) patients and 40 age-matched controls. Plasma vitamin A was significantly lower in the CF group as compared to the controls and correlated positively with plasma retinol-binding protein (RBP) in both the CF and control groups. Plasma zinc of the CF group was not significantly lower than controls whereas hair zinc was. Plasma zinc was positively correlated with plasma RBP, vitamin A, and albumin in the CF group but not in the controls. Plasma concentrations of vitamin A, RBP, albumin, and zinc decreased with age in the CF group but not in the controls. The data support previous suggestions that low plasma vitamin A levels in CF are due to defects in the retinol transport system. The zinc status of the CF groups as a whole was judged to be low-normal however a subgroup of CF patients were in the marginal to deficient category. This subgroup also had lower levels of plasma vitamin A and RBP. The data suggest that zinc may be a contributing factor in the low plasma vitamin A/RBP levels of CF patients with marginal or deficient zinc status.