Effects of oral contraceptives on vitamin A metabolism in the human and the rat

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Abstract
In this study, the effects of oral contraceptives (OC) on vitamin A metabolism in the human and rat were examined. Data obtained from the human study showed that the mean plasma vitamin A levels and basal body temperature of females taking OC were significantly higher than control subjects. However, there was no statistical correlation between the vitamin A levels and basal body temperature. The elevation of plasma vitamin A levels in the OC subjects was found not to be due to variation in dietary vitamin A intake or blood hematocrit values. The physiologic implication of the higher plasma vitamin A levels in the OC subjects is not clear. In the rat, Ovral, an OC agent, given as a saline suspension by stomach intubation daily for 4 weeks did not have any effect on plasma vitamin A. However, it markedly raised the liver vitamin A depletion rate and the rate of utilization of the vitamin. This indicated that rats given OC had a higher vitamin A requirement level. Whether oral contraceptives do alter vitamin A requirement in the human remains to be investigated.