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
Haskell, M.J.; Pandey, P.; Graham, J.M.; Peerson, J.M.; Shrestha, R.K.; Brown, K.H.
American Journal of Clinical Nutrition 81(2): 461-471
2005
ISSN/ISBN: 0002-9165 PMID: 15699236 DOI: 10.1093/ajcn.81.2.461Document Number: 556809
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 microgram retinol equivalents/d as retinyl palmitate, vitamin A-fortified rice, goat liver, amaranth leaves, or carrots or 2000 microgram 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 +/- 0.04 to -1.42 +/- 0.02 log cd/m2, and the final mean PT did not differ significantly from that in the nonnightblind women (-1.43 +/- 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 +/- 0.05 to 1.07 +/- 0.05 micromol/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.