Nutrition and the pill
Apart from their gynecologic influence as birth control agents, oral contraceptives (OCs) have been shown to affect a number of metabolic and nutritional processes, some insignificantly and others beneficially. The use of contraceptive pills has been shown to decrease the physiologic levels of six nutrients--riboflavin, pyridoxine, folacin, vitamin B12, ascorbic acid and zinc--and to increase the levels of four others--vitamin C, iron, copper and vitamin A. Women who take OCs and have adequate diets need little or no supplemental vitamins. Vitamin and mineral increases caused by OCs do not require treatment.
J Reprod Med. 1984 Jul;29(7 Suppl):547-50. PMID: 6481708