A study published in the American Journal of Clinical Nutrition (November 2004 80(5):1299-1307) shows in women who are pregnant, both zinc and B-carotene are necessary for proper levels of Vitamin A. Furthermore, supplementation of these nutrients during pregnancy can affect vitamin A status in the infant. Vitamin A supplementation during pregnancy in higher doses is contraindicated because of the possibility of birth defects. However, B-carotene is a precursor to vitamin A and can be converted to vitamin A in the body and is safe during pregnancy. Recent evidence has shown that B-carotene on its own is not well absorbed and is not converted to vitamin A. In this study, researchers have determined that zinc supplementation, along with B-carotene provides improved levels of vitamin A.
Researchers conducted a double-blind, placebo-controlled study of 170 mothers and their infants. The mothers were divided into groups, all given 30mg of iron and 0.4mg of folic acid supplements. One group was also given 4.5mg of B-carotene, a second given 30mg of zinc sulfate, a third given 4.5mg of B-carotene and 30mg of zinc, and the fourth no additional supplements. They were followed up at 1 month and 6 months post-delivery.
The results showed plasma retinol (vitamin A) concentrations at 6 months (postpartum) were significantly higher in the women who received zinc during pregnancy than in the women who did not receive zinc. As well, the plasma retinol concentrations of infants of mothers supplemented during pregnancy with B-carotene and zinc were significantly higher than those of infants from all other groups and reduced Vitamin A deficiency by >30%. Supplementation with B-carotene alone did not significantly affect retinol levels. In breast-milk, retinol concentrations were higher only in women who received B-carotene and zinc. There was no adverse effect on iron status.
The authors conclude that supplementation with B-carotene is only effective in improving vitamin A status when given in combination with zinc, which is the first time this effect has been recorded. Zinc may improve absorption of B-carotene and can impact transport and storage of both B-carotene and vitamin A. This study points out the importance of using high quality pre-natal vitamins that have adequate amounts of zinc, especially in mothers at risk for nutrient deficiencies.
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