Vitamin B-6 Status in Unsupplemented Pregnant Women Is Associated Positively with Serum Docosahexaenoic Acid and Inversely with the n-6-to-n-3 Fatty Acid Ratio.

BACKGROUND

Vitamin B-6-deficient diets decrease plasma docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (AA) concentrations in healthy adults. These fatty acids (FAs) are important for fetal neurodevelopment, but the relation between vitamin B-6 status and circulating polyunsaturated FAs (PUFAs) during pregnancy is unknown.

OBJECTIVE

We sought to assess the relation between plasma pyridoxal 5' phosphate (PLP; the active form of vitamin B-6) and serum DHA, EPA, AA, linoleic acid, eicosadienoic, and α-linolenic acid concentrations during pregnancy.

METHODS

A prospective cohort study in 186 healthy pregnant Brazilian women (aged 20-40 y) who were not using supplements was conducted in Rio de Janeiro, Brazil. Participants were enrolled in the first trimester of pregnancy (5-13 gestational weeks) and were followed up twice between 20-26 and 30-36 wk of gestation. Longitudinal linear mixed-effects regression models were used to evaluate the associations between 1) first-trimester PLP and PUFA concentrations across pregnancy and 2) ΔPLP (i.e., difference between third- and first-trimester plasma PLP concentrations) and PUFA concentrations across pregnancy. Models were adjusted for gestational week, first-trimester body mass index, smoking habit, and dietary intakes of vitamin B-6, fish, total fat, and PUFAs.

RESULTS

Plasma PLP concentrations (median, IQR) substantially declined during pregnancy from 35.8 nmol/L (28.6-44.3 nmol/L) in the first trimester to 21.0 nmol/L (15.8-26.3 nmol/L) in the second trimester, and 16.8 nmol/L (12.9-20.3 nmol/L) in the third trimester (both P < 0.0001). Changes in plasma PLP concentrations across trimesters were positively associated with serum DHA concentrations (β = 0.252, P = 0.012) and inversely associated with serum n-6-to-n-3 (ω-6-to-ω-3) FA ratio (β = -0.010; P = 0.015), after adjustments for confounders.

CONCLUSIONS

Maternal vitamin B-6 status during pregnancy was positively associated with the circulating concentration of DHA and inversely associated with n-6:n-3 FAs in Brazilian women who were not taking vitamin supplements. Further study is required to determine the impact of poor vitamin B-6 status on fetal neurodevelopment.