Serum Vitamin B₁₂Binding Capacity and Oral Contraceptive Hormones

Oral contraceptive use: impact on folate, vitamin B6, and vitamin B12 status

“…For example, in most studies there were no controls for dietary folate intake, vitamin supplement use, smoking, or alcohol use. [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] In addition, other factors not considered by many investigators include differences in the specific type of hormone used in the OCs, 58,59 compliance with the OC regimen, 44,58,59 and duration of OC use. 50,58 Folate status in these earlier studies was, in most cases, based solely on a comparison of serum folate concentration between groups of OC users and non-users.…”

“…It is likely that the inconsistency between these early studies may be due to lack of control of potentially confounding variables. For example, in most studies there were no controls for dietary folate intake, vitamin supplement use, smoking, or alcohol use 39–57 . In addition, other factors not considered by many investigators include differences in the specific type of hormone used in the OCs, 58,59 compliance with the OC regimen, 44,58,59 and duration of OC use 50,58 .…”

Oral contraceptives and the red blood cell

“…In addition, the implications of an elevated serum vitamin B12 binding capacity in OC users is unclear. 2 Further studies on the relationship between vitamin B12 metabolism and oral contraceptives are indicated and may help explain the etiology of this papers' findings.…”

Metabolic effects of combined oral contraceptives

“…Vitamin B l2 concentrations have been reported to be reduced in the serum but not in the erythrocytes of oral contraceptive users [111][112][113][114]. The reason for this is uncertain, but a number of possible causes have been suggested, including malabsorption and increased renal excretion.…”