Higher Than Recommended Folic Acid Intakes is Associated with High Folate Status Throughout Pregnancy in a Prospective French-Canadian Cohort

Abstract

Background: Folate and vitamin B12 status during pregnancy are important for maternal and neonatal health. Maternal intake and prepregnancy body mass index (ppBMI) can influence biomarker status.

Objectives: This study aimed to, throughout pregnancy; 1) assess folate and B12 status including serum total folate, plasma total vitamin B12, and homocysteine (tHcy); 2) examine how these biomarkers are associated with intakes of folate and B12 and with ppBMI; and 3) determine predictors of serum total folate and plasma total vitamin B12.

Methods: In each trimester (T1, T2, and T3), food and supplement intakes of 79 French-Canadian pregnant individuals were assessed by 3 dietary recalls (R24W) and a supplement use questionnaire. Fasting blood samples were collected. Serum total folate and plasma total vitamin B12 and tHcy were assessed by immunoassay (Siemens ADVIA Centaur XP).

Results: Participants were 32.1 ± 3.7 y and had a mean ppBMI of 25.7 ± 5.8 kg/m². Serum total folate concentrations were high (>45.3 nmol/L, T1: 75.4 ± 55.1, T2: 69.1 ± 44.8, T3: 72.1 ± 52.1, P = 0.48). Mean plasma total vitamin B12 concentrations were >220 pmol/L (T1: 428 ± 175, T2: 321 ± 116, T3: 336 ± 128, P < 0.0001). Mean tHcy concentrations were <11 μmol/L across trimesters. Most participants (79.6%-86.1%) had a total folic acid intake above the Tolerable Upper Intake Level (UL, >1000 μg/d). Supplement use accounted for 71.9%-76.1% and 35.3%-41.8% of total folic acid and vitamin B12 intakes, respectively. The ppBMI was not correlated with serum total folate (P > 0.1) but was weakly correlated with and predicted lower plasma total vitamin B12 in T3 (r = -0.23, P = 0.04; r² = 0.08, standardized beta [sβ] = -0.24, P = 0.01). Higher folic acid intakes from supplements predicted higher serum total folate (T1: r² = 0.05, sβ = 0.15, P = 0.04, T2: r² = 0.28, sβ = 0.56, P = 0.01, T3: r² = 0.19, sβ = 0.44, P < 0.0001).

Conclusions: Most pregnant individuals had elevated serum total folate concentrations, reflecting total folic acid intakes above the UL driven by supplement use. Vitamin B12 concentrations were generally adequate and differed by ppBMI and pregnancy stage.

Keywords: folate; folic acid; homocysteine; pregnancy; prepregnancy body mass index; vitamin B12.