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

Abstract

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.

PIP: A 3-phase study was conducted to evaluate the Vitamin B6 nutritional requirement of oral contraceptive users. 8 young women (mean age, 20 years; mean body weight, 63.2 kg.) on oral contraceptives (OCs) served as the study group and another 8 (mean age, 21 years; mean body weight, 61.4 kg.) not on OCs served as controls. The 1st 10 days of the study were designated as the predepletion phase: all subjects were given a basal diet with supplement of 1.7 mg/day pyridoxine hydrochloride (PN-HCL). The depletion phase consisted of withdrawing Vitamin B6 supplement of 1.7 mg/day for 32 days; the repletion phase consisted of supplementing the basal diet with specific amounts of PN-HCL (intakes of 0.96, 1.56, and 5.06 mg were taken for 8,9, and 7 days, respectively). Only the study group went through the depletion and repletion phases. Fasting blood samples and continous 24-hour urine samples were obtained for analysis. The Vitamin B6 nutriture was measured by erythrocyte pyridoxal level, erythrocyte alanine aminotransferease and erythrocyte aspartic aminotransferase activity. The results indicated that 0.96 mg Vitamin B6 was insufficient to meet nutritional requirements of OC users. Almost all subjects reached a predepletion level at an intake of 1.5 mg/day. An intake of between 1.5 and 5.0 mg/day of Vitamin B6 was deemed sufficient for OC users, and compares favorably with nonusers' measurement of 1.5 mg/day.