Prevalence and determinants of suboptimal vitamin B6 status in young adult women in Metro Vancouver

Abstract

BackgroundVitamin B6 (B‐6) adequacy is crucial for life‐long health. The biologically active form of B‐6, pyridoxal 5′‐phosphate (PLP), plays an essential role in the metabolism of amino acids, synthesis of neurotransmitters, regulation of energy homeostasis, and metabolism of heme. Suboptimal B‐6 status – defined as having plasma PLP concentration between 20–30 nmol/L – has been associated with an increased risk of cardiovascular disease and breast, prostate, and colorectal cancer. Maternal B‐6 status has been positively associated with infant birth health determined by the Apgar Score. Low preconceptional B‐6 status has been associated with an increased risk of preterm birth, early pregnancy loss, and reduced probability of conception. Given an estimated 50% of pregnancies are unplanned, it is important for women to maintain an adequate B‐6 status throughout reproductive years. In the US National Health and Nutrition Examination Survey (NHANES 2003–2004), over 40% of B‐6 deficiency – defined as having plasma PLP concentration <20 nmol/L – was reported in childbearing‐aged women (21–44 y). Despite the crucial role of B‐6 in health, there are few data on B‐6 status among Canadian women.ObjectiveTo assess the prevalence of B‐6 deficiency and determinants of B‐6 status in childbearing‐aged women in Metro Vancouver, British Columbia.MethodsData were derived from a descriptive cross‐sectional study using convenience sampling of self‐reported healthy, non‐pregnant women (19–35 y; n= 202) residing in Metro Vancouver. The enrolment was conducted between 2012 and 2013 (Quay et al. 2015 APNM). Vitamin B‐6 status was assessed by determining fasting plasma PLP concentrations. Information on demographic, lifestyle and dietary intake was collected through validated questionnaires.ResultsThe prevalence of B‐6 deficiency (plasma PLP < 20 nmol/L) was 1.5% and that of suboptimal B‐6 status (plasma PLP between 20–30 nmol/L) was 10.9% in these healthy women of European (73%) and South Asian (27%) descent. Mean (± SD) plasma PLP concentration was 61 ± 2.1 nmol/L. Overall, the subjects were highly educated (28% > bachelor's degree; 72% ≤ bachelor's degree) and 23% reported the use of B6 containing vitamin supplements. Body mass index (p value < 0.05), ethnicity (p value < 0.05), dietary B‐6 intake (p value < 0.05) and the use of supplemental B‐6 (p value < 0.001) were significant determinants of plasma PLP concentrations. Mean dietary B‐6 intake was 1.5 ± 0.45 mg/d; and 21% had a dietary B‐6 intake below the estimated average requirement (EAR; 1.1mg/day).ConclusionThe overall 12.4% of low B‐6 status (plasma PLP < 30 nmol/L) indicates a need for investigating B‐6 status in a representative sample of Canadians. Ethnicity, dietary B‐6 intake and the use of supplemental B‐6 should be considered as covariates in future studies.Support or Funding InformationSupported by the ‘Food Nutrition and Health Vitamin Research Fund’, Faculty of Land and Food Systems, The University of British Columbia