Oral contraceptives and Vitamins
The oral contraceptives are reported to raise serum levels of vitamin A, and lower levels of ascorbic acid, cyanocobalamin, folic acid and pyridoxine. Ascorbic acid can raise serum ethinyloestradiol levels and pyridoxine may relieve depression in women on oral contraceptives, but the general clinical importance of concurrent treatment with these vitamins is uncertain.
Clinical evidence, mechanism, importance and management
There is evidence that the use of oral contraceptives can cause a biochemical deficiency of several vitamins, but clinical deficiency does not necessarily manifest itself. Serum levels of cyanocobalamin can be lowered, folate deficiency with anaemia can occur, and reduced levels of ascorbic acid and pyridoxine have been described. Treatment of pyridoxine deficiency has been shown to improve the mood of depressed women on oral contraceptives. Raised levels of vitamin A has also been reported. These changes in vitamin requirements induced by the oral contraceptives are reviewed in detail elsewhere.
A study has shown that 1 g ascorbic acid can substantially raise serum ethinyloestradiol levels (+48% measured at 24 h) in women taking oral contraceptives, and a single case report describes a woman on logynon who experienced heavy break-through bleeding within 2-3 days of stopping her self-administered 1 g daily dose of ascorbic acid.
Routine prophylactic treatment with vitamins in women on oral contraceptives has been advised by some, but questioned by others because an increased intake of some vitamins in some circumstances may be harmful. For example, in areas of the world where protein malnutrition is rife, a pyridoxine supplement might lead to an undesirable increase in amino-acid catabolism in those on a low daily intake of protein. One author's comment on the indiscriminate supplementation of the diet with multivitamin preparations in women on oral contraceptives is that it can hardly be justified.