Study: Zinc (2001) & Night Blindness



Learn more about night blindness.

It is known that vitamin A deficiency contributes to night blindness. It is especially a problem in developing nations where nutritional deficiencies may be common.

Researchers wanted to assess whether zinc played a role in night blindness or in the functioning of vitamin A. They examined about 200 women who were reporting night blindness during their pregnancies. They were divided, randomly, into six groups to receive specific nutrients for a three week period:

  • Vitamin A and placebo
  • Vitamin A and 25mg zinc
  • Beta-carotene (beta-carotene is a precursor to vitamin A)
  • Beta-carotene and 25mg zinc
  • Zinc and placebo
  • Two placebos

The women were assessed as to how well they could see in dim light, how well they could adapt to changes in light, and blood samples were taken at the beginning and at the conclusion of the study. Their use of the supplements and daily reportings of night blindness were taken at home by visiting medical professionals twice a week during the 3-week period.

They found that supplementing with zinc improved the levels of zinc in the blood, but did not, by itself improve night vision. Women receiving both zinc and vitamin A with previous low levels of zinc reported improvement in their night vision, reported four times as often as reported by the women receiving placebo. They also had a small improvement in how well they could see in dim light.

The researchers concluded that zinc may improve the effect of vitamin A in improving night blindness.

Researchers: P. Christian, S.K. Khatry, et al
Published: Zinc supplementation might potentiate the effect of vitamin A in restoring night vision in pregnant Nepalese women, American Journal of Clinical Nutrition, June, 2001.