Zinc supplementation might potentiate the effect of vitamin A in restoring night vision in pregnant Nepalese women

Am J Clin Nutr. 2001 Jun;73(6):1045-51. doi: 10.1093/ajcn/73.6.1045.

Abstract

Background: Zinc deficiency may result in abnormal dark adaptation or night blindness, a symptom primarily of vitamin A deficiency. During a placebo-controlled trial in Nepal, weekly vitamin A supplementation of women reduced but failed to eliminate the incidence of night blindness during pregnancy, suggesting a role for zinc.

Objective: The study examined the efficacy of daily zinc supplementation in restoring night vision of pregnant women who developed night blindness while routinely receiving either vitamin A, beta-carotene, or placebo in a field trial.

Design: Women (n = 202) who reported to be night blind during pregnancy were randomly assigned in a double-blind manner, stratified on vitamin A, beta-carotene, or placebo receipt, to receive 25 mg Zn or placebo daily for 3 wk. Thus, the 6 groups studied were as follows: beta-carotene + zinc, beta-carotene alone, vitamin A + zinc, vitamin A alone (vitamin A + placebo), zinc alone (zinc + placebo), and placebo (2 placebos: one for the vitamin A or beta-carotene study and one for the zinc study). Women underwent a clinic-based assessment that included pupillary threshold testing and phlebotomy before and after supplementation. Supplement use and daily history of night blindness were obtained at home twice every week.

Results: Zinc treatment increased serum zinc concentrations, but alone (zinc alone group), failed to restore night vision or to improve dark adaptation. However, women in the vitamin A + zinc group who had baseline serum zinc concentrations <9.9 micromol/L were 4 times more likely to have their night vision restored (95% CI: 1.1, 17.3) than were women in the placebo group and tended to have a small improvement in pupillary threshold scores (by 0.21 log candela/m2; P = 0.09).

Conclusion: These data suggest that zinc potentiated the effect of vitamin A in restoring night vision among night-blind pregnant women with low initial serum zinc concentrations.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Double-Blind Method
  • Drug Synergism
  • Female
  • Humans
  • Nepal
  • Night Blindness / drug therapy*
  • Pregnancy
  • Pregnancy Complications / drug therapy*
  • Reflex, Pupillary / drug effects*
  • Regression Analysis
  • Treatment Outcome
  • Vitamin A / therapeutic use*
  • Vitamin A Deficiency / complications*
  • Zinc / blood
  • Zinc / deficiency
  • Zinc / therapeutic use*
  • beta Carotene / administration & dosage
  • beta Carotene / therapeutic use

Substances

  • beta Carotene
  • Vitamin A
  • Zinc