Sub-50 Oral Contraceptives Affect Folate Kinetics

Abstract

The effects of long-term use of oral contraceptives containing less than 50 µg of estrogen (sub-50 OCs) on the kinetics of folic acid monoglutamate, vitamin B₁₂ levels, and iron status have been studied in 29 OC users (Marvelon®) and in 13 women without OC use serving as controls. At 210 min after oral folate loading the median serum folate concentration was significantly lower in OC users when compared to the control group. OC users showed significantly higher total iron binding capacity and significantly lower serum vitamin B₁₂ concentrations. This data demonstrates that sub-50 OCs significantly affect folate kinetics and vitamin B₁₂ levels. However, the folate and vitamin B₁₂ status does not seem to be at risk.

Oral Estradiol Decreases Plasma Homocysteine, Vitamin B6, and Albumin in Postmenopausal Women But Does Not Change the Whole-Body Homocysteine Remethylation and Transmethylation Flux

“…The post hoc analyses suggested that all three might be important here. First, vitamin B 6 levels decreased during treatment, an effect that has also been shown in oral contraceptive users (36). This might seem contradictory because vitamin B 6 is a cofactor in the transsulfuration pathway, which thereby could be impaired as well.…”

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.…”

“…32 More recently conducted studies, designed to evaluate the effect of OC use on folate status, have included measures of RBC folate concentration; however, as with studies measuring only serum folate concentration, the results have been equivocal. [46][47][48]50,51,[60][61][62] In the studies from which it was concluded that OC use negatively affected folate status, none controlled for all potentially confounding variables, including differences in dietary intake and use of folic acid-containing supplements. 46,48,60,62 Of those studies that controlled for dietary intake, with one exception, 62 no difference in RBC folate concentration between OC and non-OC users was detected.…”

“…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 .…”

Serum Folate and Cobalamin Levels in Women Using Combined Contraceptive Vaginal Ring

“…The information that is available in the literature concerning the serum levels of folate (folic acid) in women using oral contraceptive pills is still somewhat conflicting. Some studies have shown diminished serum or plasma concentrations of fo-late in users of oral contraceptives when compared to controls [23,24], whereas others have found similar levels of folate in oral contraceptive users and non-pregnant female volunteers [25][26][27][28][29]. These divergent observations are hard to reconcile.…”