Supplementation with iron and riboflavin enhances dark adaptation response to vitamin A–fortified rice in iron-deficient, pregnant, nightblind Nepali women

Abstract

Background: Nightblindness affects 16–52% of pregnant women in areas of Nepal and in some cases persists after vitamin A treatment. Iron and riboflavin affect vitamin A utilization and photoreceptor function, respectively, and pilot data in the study population showed a high prevalence of iron and riboflavin deficiencies.Objective: The objective was to assess the effect of supplemental iron and riboflavin on pupillary threshold (PT) and plasma retinol in nightblind, pregnant Nepali women given vitamin A–fortified rice.Design: Nightblind pregnant women were randomly assigned to receive, 6 d/wk under supervision for 6 wk, a vitamin A–fortified rice curry dish providing 850 μg retinal activity equivalents/d with either a 30-mg Fe and 6-mg riboflavin (FeR + VA) capsule or a placebo control (VA only) capsule. Hemoglobin, erythrocyte riboflavin, and plasma ferritin and retinol were measured before and after the intervention. Dark adaptation was assessed by PT score.Results: Women who were iron deficient at baseline (n = 38) had significantly greater improvement in PT score with iron and riboflavin supplementation than without (P = 0.05). Iron and riboflavin supplements significantly reduced the prevalences of riboflavin deficiency (from 60% to 6%; P < 0.0001), iron deficiency anemia (from 35% to 15%; P < 0.007), and abnormal PT (from 87% to 30%; P < 0.05) from baseline. Mean increases in erythrocyte riboflavin (P < 0.0001) and plasma ferritin (P = 0.01) were greater in the FeR + VA group than in the VA only group.Conclusions: Iron deficiency may limit the efficacy of vitamin A to normalize dark adaptation in pregnant Nepali women. Further studies are needed to assess the effect of simultaneous delivery of iron and vitamin A for the treatment of nightblindness.