Implications of oral contraceptive use on vitamin nutritional status.
Cross-sectional and longitudinal studies were made to assess vitamin nutritional status of women using oral contraceptives (OCs). In the cross-sectional study, data obtained on 20 women, who had used Ovulen 50 for 6-12 months, were compared with data obtained on matched controls who had never used OCs. In the longitudinal study, 23 women were examined initially (before OC use) and again at 1 or more points during the next 6 months of OC use. Changes were found in several parameters of nutrition tested. 1) OC use produced a highly significant rise in plasma vitamin A within 1 month of treatment. 2) Thiamine activity measurements showed a slight fall, but did not affect the TPP effect, suggesting that OCs did not seriously alter thiamine status. 3) Erythrocyte riboflavin concentration showed a fall, revealing a very high incidence (> 80%) of biochemical riboflavin deficiency in women before starting OCs which was further reduced after treatment. 4) There was a marked rise in urinary excretion of xanthuremic and kynurenic acids after a standard tryptophan load, indicating impaired tryptophan metabolism due to pyridoxine deficiency. 5) Erythrocyte folate levels showed a small but significant fall. These observations on Indian women belonging to low income groups show clearly that OC use does affect the vitamin economy of the body adversely. Biochemical evidence presented argues that OCs alter vitamin economy through rise in levels of some proteins which bind vitamins. Vitamin supplements are recommended not only for patient benefit but for program acceptability.