The vitamin B6 requirement in oral contraceptive users. I. Assessment by pyridoxal level and transferase activity in erythrocytes.

Eight college-age women using estrogen-containing oral contraceptives (OC) were fed a low vitamin B6 diet (0.36 mg/day) for 42 days. During the first 10 days (adjustment period) the diet was supplemented with 1.7 mg pyridoxine hydrochloride bringing the total intake to 2.06 mg/day. Following depletion, repletion was done in three consecutive steps: intakes of 0.96, 1.56, and 5.06 mg were consumed for 8, 9, and 7 days, respectively. Continuous 24-hr urine collections were made throughout the study and fasting blood samples were drawn periodically. Vitamin B6 nutriture was assessed by erythrocyte pyridoxal level, erythrocyte alanine aminotransferase and erythrocyte aspartic aminotransferase activity; and stimulation of these enzyme systems with pyridoxal phosphate. Results were compared with data obtained from non-OC users who consumed a similar diet. The data obtained suggest that 0.96 mg vitamin B6 was not adequate to meet the needs of OC users. Predepletion levels had been reached in almost all subjects at an intake of 1.5 mg/day. Assessed by the parameters studied, an intake between 1.5 and 5.0 mg/day of vitamin B6 was adequate to meet the needs of OC users; this compares with 1.5 mg/day previously suggested for the nonuser.