Oral contraceptives: effect of long-term use on liver vitamin A storage assessed by the relative dose response test

Vitamin A status measured by the relative dose response (RDR) test was determined among groups of Northern Thai women who had used estrogen-containing oral contraceptives (OCs) with or without multivitamin supplements through 13 cycles. Mean serum vitamin A values were elevated approximately 40% above those of control subjects (intrauterine contraceptive device (IUCD) users) during OC usage. Daily (one capsule) or periodic (two capsules 7 d/mo) multivitamin supplementation that included 1700 micrograms vitamin A per capsule did not significantly influence vitamin A serum values. The RDR test after 13 cycles was elevated in one individual who had taken OCs and the periodic multivitamin supplement. It reverted to normal after supplementation with vitamin A. A single high-dose vitamin A supplement (68,000 micrograms) did not change circulating levels of the vitamin. Among this population there is little evidence that use of estrogen-containing OCs for greater than 1 y resulted in a physiologically significant deterioration of vitamin A status.