Recovery from impaired dark adaptation in nightblind pregnant Nepali women who receive small daily doses of vitamin A as amaranth leaves, carrots, goat liver, vitamin A-fortified rice, or retinyl palmitate

Background: It is not known whether daily consumption of vitamin A-containing foods is efficacious for treating nightblindness. Objective: We assessed the effect of supplementation with vitamin A from food or synthetic sources on dark adaptation and plasma retinol concentrations in nightblind pregnant Nepali women. Design: Nightblind pregnant women were randomly assigned to 1 of 6 treatment groups to receive 6 d/wk for 6 wk either 850 [micro]g retinol equivalents/d as retinyl palmitate, vitamin A-fortified rice, goat liver, amaranth leaves, or carrots or 2000 [micro]g retinol equivalents/d as retinyl palmitate. Dark adaptation was assessed weekly by using the pupillary threshold (PT) test: plasma retinol concentrations were measured before and after the intervention. These outcomes were also assessed in a comparison group of nonnightblind pregnant women. Results: In the nightblind women, the mean PT improved significantly (P < 0.0001) from -0.71 [+ or -] 0.04 to -1.42 [+ or -] 0.02 log cd/[m.sup.2], and the final mean PT did not differ significantly from that in the nonnightblind women (-1.43 [+ or -] 0.04: P = 0.55). Improvement in dark adaptation was greater in the liver group than in the vitamin A-fortified rice group (P < 0.02). Plasma retinol concentrations increased significantly (P < 0.0001) from 0.95 [+ or -] 0.05 to 1.07 [+ or -] 0.05 [micro]mol/L. The plasma retinol response was greater in the higher-dose capsule and liver groups than in the vegetable groups and significantly greater in the liver group than in the vitamin A-fortified rice group (both: P < 0.05). Conclusion: Improvement in dark adaptation did not differ significantly between women who received vitamin A as liver, amaranth leaves, carrots, or retinyl palmitate. KEY WORDS Nightblindness, pregnancy, vitamin A status, supplementation, pupillary threshold, dark adaptation, Nepal, vitamin A, [beta]-carotene, food-based interventions