Rothman, cautioned that many commercial multivitamins contain 10, IU of Vitamin A, enough to push women into the dangerous range, and that some contain as much as 25, IU. He emphasized, however, that there are no known adverse effects of Vitamin A at the maximum recommended levels--about 8, IU per day for pregnant women--and that moderate amounts of the vitamin are crucial for normal development of the fetus. But among the children of women who took more than 10, IU per day, he said, one in every 57 suffered defects ranging from cleft lips and palates to severe heart defects, about twice the rate among mothers who consumed less than 10, IU.
The council, he noted, has recommended since that pregnant women consume no more than 8, IU per day. But biochemist James A. Olson of Iowa State University warned that publicity about the study may do more harm than good if women reduce their Vitamin A intake too much.
They make up for [essential nutrients] that are not gotten from the diet. But virtually everyone agreed that there may be an easy way out of the dilemma: switching from supplements containing Vitamin A to those containing beta carotene, an antioxidant vitamin that is beneficial to the heart and that is converted to Vitamin A in the body.
It is also present in a variety of vegetables. Beta carotene has not been shown to have any adverse effects in either adults or fetuses, and the body only converts as much of it to Vitamin A as it actually needs. The great vessels, the aorta, and the pulmonary artery arise from the growth of a septum in the truncus arteriosis. This septum arises from conotruncal swellings, which receive a contribution from the neural crest. Thus, the distinction in this study may be between neural crest-related and neural crest-unrelated cardiac outflow tract abnormalities.
Vitamin A intake in the Baltimore-Washington Heart Study was evaluated by reported maternal food preferences for the year prior to conception. Supplement use also was recorded. There was no significant association between vitamin A intake and outflow tract defects with normal great vessels. The lack of relationship of high intake of vitamin A from food is curious, and may have been due to errors from the use of food preference recall for the year prior to pregnancy. After all, dietary preferences may change during pregnancy, a fact acknowledged by the authors.
Vitamin A from food may be less bioavailable than vitamin A from supplements; serum retinol levels have been shown to be increased more by ingestion of a supplement than by ingestion of liver with comparable vitamin A content.
So how much vitamin A is safe? The evidence for an adverse effect of supplemental vitamin A in doses less than 10, IU is weak, but there is no reason to use high-dose supplementation during pregnancy.
Some nutritional advice, however, may be warranted too. Department of Health has recommended that liver consumption be avoided entirely in early pregnancy. There is concern that the U. Alternative sources of retinol are full-fat dairy foods, egg yolks, and fatty fish including herring, sardines, anchovies, salmon, mackerel, and bluefish. Other strategies include deriving most nutritional vitamin A from carotenoids in vegetables, and avoiding vitamin A supplements altogether.
Conflict of Interest Statement: In the year after the Rothman study appeared, I was recruited by Hoffman-LaRoche, a manufacturer of vitamin A, to serve on a panel charged with considering the experimental and epidemiology data on the developmental effects of supplements.
The meeting was held in Boston and included tickets to an absolutely superb performance by the Boston Symphony. Although this experience may be interpreted as having produced a biased point of view, as of this writing, Hoffman-LaRoche has not paid the honorarium that was promised, producing at least as strong a potential bias in the opposite direction, the Boston Symphony notwithstanding.
Cohlan SQ. Congenital anomalies in the rat produced by the excessive intake of vitamin A during pregnancy. Pediatrics ; Geelen JA. Hypervitaminosis A induced teratogenesis. Fantel AG, et al. Teratogenic effects of retinoic acid in pigtail monkeys Macaca nemestrina. General features. Teratology ; Kamm JJ. Toxicology, carcinogenicity, and teratogenicity of some orally administered retinoids. J Am Acad Dermatol ; DiGiacomo RF, et al. Hypervitaminosis A and reproductive disorders in rabbits.
Lab Anim Sci ; Saillenfait AM, Vannier B. Methodological proposal in behavioural teratologenicity testing: Assessment of propoxyphene, chlorpromazine, and vitamin A as positive controls. Hendrickx AG, et al. Vitamin A teratogenicity and risk assessment in the cynomolgus monkey. Hypervitaminosis A and congenital renal anomalies in a human infant. Obstet Gynecol ; Pilotti G, Scorta A. Hypervitaminosis A in pregnancy and neonatal malformations of the urinary tract [in Italian].
Hutchings, D. Gibbon, and M. Kauffman Maternal vitamin A excess during the early fetal period: effect on learning and development in the offspring. Irving, D. Willhite, and D. Burk Morphogenesis of isotretinoin-induced microcephaly and micrognathia studied by scanning electron microscopy.
Kamm, J. Ashenfelter, and C. Ehmann Preclinical and clinical toxicology of selected retinoids. In: The Retinoids. Roberts, and D. Academic Press, New York, vol. Kochhar, D. Acta Pathol. I Analysis of teratogenic effects of retinoic acid. McBride Isotretinoin metabolism and its role in teratogenesis in mice and marmosets.
Teratology, C. Kwarta, R. Kimmel, G. Kimmel, and W. Kwasigrouch, T. Kochhar Locomotory behavior of limb bud cells. Effects of excess vitamin A in vivo and in vitro. Cell Res. Lammer E. Opitz The DiGeorge anomaly as a developmental field defect. Lammer, E. Chen, R. Hoar, N. Agnish, P. Benke, J. Braun, C. Curry, P.
Fernhoff, A. Crix, LT. Lott, J. Richard, and S. Sun Retinoic acid embryopathy. Maden, M. Summerbell Retinoic acid-binding protein in the chick limb bud: Identification at developmental stages and binding affinities of various retinoids. Marin-Padilla, M. Ferm Somite necrosis and developmental malformations induced by vitamin A in the golden hamster. J Embryol. Mooney, M. Hoyenga K. Hoyenga, and J. Morton Prenatal hypovitaminosis A and postnatal behavioral development in the rat.
Morriss, G. Neubert and H. Merker, eds. Thieme, Stuttgart, pp. Olsen, J. Bridges, L. Packer, F. Chytil, and G. Wolfe The function of Vitamin A. Pauling, L. Freeman and Co. New York. Roche Laboratories July, Letter to physicians. Rosa, F. Wilk, and F. Kelsey Vitamin A congeners. Russell-Briefel, R.
Caggiula, and L. Kuller A comparison of three dietray methods for estimating vitamin A intake. Shenefelt, R;E.
Relation to dose and stage at treatment. Shepard, T. Edition 1. Sporn, M. Roberts Role of retinoids in differentiation and carcinogenesis. Cancer Res. I and II. Academic Press, New York. Stein, Z. Kline, and M.
Kharrazi What is a teratogen? Thorogood, P. Smith, A. Nicot, R. McGinty, and D. Garrod Effects of vitamin A on the behavior of migratory neural crest cells in vitro. Cell Sci. Underwood B. In: The Retinoids, Vol. B Sporn, A. Academic press, New York, pp. Underwood, B. Vorhees, C.
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