Vitamin A (2000, 2005) & Night Blindness
Learn more about night blindness.
Previous research has demonstrated that vitamin A supplementation can reverse the effects of night blindness. In this study researchers wanted to evaluted whether a diet contained small amounts of vitamin A would also have a beneficial effect.
The researchers compared supplementing with vitamin A in food sources versus supplementing with vitamin A, measuring the results by evaluating both dark adaption and plasma (blood) retinol levels in Napali women who suffered from night blindness.
The women were divided into six groups, receiving various forms of vitamin A in vitamin A-fortified rice, retinyl palmitate, amaranth leaves, goat liver, or carrots. They were evaluated weekly via degree of pupil dilation and blood reinol levels. The groups were also compared to women who were not experiencing night blindness.
The researchers found that night blindness diminished most in the group receiving goat liver compared to the vitamin A-fortified rice group. The blood retinol level change was greater in those receiving retinyl palmitate and liver groups than in the vegetable groups, and greater in the group receiving goat liver than in the group receiving vitamin A-fortified rice.
The researchers concluded that all of the methods decreased night blindness, and those methods with better results were not significantly so. Both dietary vitamin A and vitamin A supplementation were effective.
Researchers: M. Haskell, P. Pandey, et al
Published: American Journal of Cliniical Nutrition, February, 2005
Researchers examined the effectiveness of treating Napali women with vitamin A and beta-carotene supplements to counter the effects of night blindness, known to researchers as "dark-adaptation threshold."
298 pregnant women aged 15-45 who experienced varying degrees of night blindness were tested in a placebo-controlled study examining the benefits of supplementation with vitamin A and beta-carotene. Almost half of them were also tested three months after they gave birth. The results were compared to 100 similarly aged American women who were not pregnant. The degree of night blindness was evaluated by looking at the amount of light needed for the pupils of the eyes to constrict after suddenly being exposed to light. The effectiveness was also evaluated by measuring blood retinol concentrations.
The researchers found that the women who were give vitamin A performed better than those receiving a placebo. The American women had better natural night vision than did the Nepali women.
The researchers concluded that successful adaption to changes in light were closely tied to serum (blood) retinol levels and markedly improved with vitamin A supplementation.
Researchers: N. Congdon, M. Dreyfuss, et al
Published: Responsiveness of dark-adaptation threshold to vitamin A and beta-carotene supplementation in pregnant and lactating women in Nepal, American Journal of Clinical Nutrition, October, 2000