Healthy Living
Vitamin A - Safety
By David Perlmutter, MD, FACN
A new study reported in the New England Journal of Medicine (November 23, 1995) entitled Teratogenicity of High Vitamin A Intake indicates that there may be significant risks associated with high dietary intake of preformed vitamin A.
The study evaluated the babies born to women who took more than 10,000 IU of preformed vitamin A per day in the form of supplements. Based upon this study, the authors estimated that the risk of significant fetal malformations was one infant in 57 in the group taking vitamin A. Many animal studies have demonstrated that high levels of preformed vitamin A may be teratogenic (cause birth defects). A synthetic compound similar to vitamin A, used in the treatment of severe acne (Retin-A) is also known to cause congenital fetal anomalies. It has been estimated that the risk of malformation of fetuses exposed to Retin-A is 25 times greater than normal.
It is very important to recognize that there is a profound chemical difference between vitamin A and beta carotene. Beta carotene is a plant synthesized precursor of vitamin A. It becomes chemically transformed into vitamin A after it is absorbed from the gut. No association with teratogenicity or other significant health consequence has been described with typical usage of beta carotene. Indeed, the authors of the study report, "Our findings indicate that vitamin A is potentially teratogenic, but these findings relate solely to the preformed vitamin A and not to beta carotene, a vitamin A precursor." They further state that "... studies in animals indicate that a high intake of beta carotene is neither toxic nor teratogenic." It is estimated in the United States that approximately 25% of adults ingest supplements containing preformed vitamin A and that about 5% take supplements of vitamin A alone. Indeed, preformed vitamin A may play an important role in the actual treatment of certain illnesses, including various skin conditions, and inflammatory diseases of the bowel.
Nevertheless, my recommendation would be that women in the childbearing years avoid taking preformed vitamin A unless it is under the supervision of a physician as part of a treatment program for a specific health problem. On the other hand, there is no reason whatsoever to avoid beta carotene, even for women who are pregnant or who are considering it.
It was quite distressing to watch the evening news when this article was first published, as viewers were no doubt left with the impression that here was an important reason for women in the childbearing years to avoid taking vitamins. Unfortunately, this type of sensationalism very likely caused many women to stop taking their multivitamins altogether. I am sure this will have consequences since over the past five years it has been clearly demonstrated that women taking multivitamins, because they contain folic acid, significantly reduce their risk of having children born with developmental abnormalities of the nervous system.
The take-home message - women in the childbearing years should take a good multivitamin that contains beta carotene (not preformed vitamin A), as well as folic acid (supplying 400 mcg per day).