Effects of oral contraceptives on vitamin metabolism

The chapter reviews the present literature available on the interactions between vitamins and oral contraceptives. The use of oral contraceptive agents (OCAs) is widespread and is being increasingly encouraged in developing countries. Their use has been associated with a number of side effects, in particular, a possible increased risk of thrombotic and embolic vascular disease. There is also evidence that OCAs may affect the metabolism of a number of vitamins. Evidence for deficiency of thiamine, riboflavin, ascorbic acid, pyridoxine, folic acid, and vitamin B₁₂, and for excess accumulation of vitamin A is reported. The normal metabolism of pyridoxine and folic acid is discussed in the chapter. Users of contraceptive steroids may develop megaloblastic anemia due to folic acid deficiency. Depression is associated with women taking oral contraceptives. A contraceptive steroid, especially estrogen, is seen to produce abnormalities in tryptophan metabolism in the great majority of women who use them.