Vitamin A supplementation increases levels of retinoic acid compounds in human plasma: possible implications for teratogenesis.

The concentrations of retinoic acid compounds were monitored by a newly developed highly sensitive HPLC procedure in plasma of six volunteers who received 833 IU vitamin A per kg body weight per day during a 20-day period. There was a significant increase of all-trans-retinoic acid (two-fold), 13-cis-retinoic acid (7-fold) and 13-cis-4-oxoretinoic acid (5-fold) over endogenous plasma levels of these retinoids. The same compounds had previously been found after treatment with the teratogenic drug isotretinoin (Roaccutan, Accutane). Our results raise the possibility that high vitamin A intake may carry a teratogenic risk attributable to increased levels of retinoic acid compounds generated from retinol by metabolic processes.