Maternal Iron and Vitamin D Status during the Second Trimester Is Associated with Third Trimester Depression Symptoms among Pregnant Participants in the APrON Cohort.

BACKGROUND: The maternal status of multiple micronutrients during pregnancy and postpartum and their potential associations with maternal health outcomes are largely undescribed. OBJECTIVES: This study aimed to examine associations between maternal iron and vitamin D status, individually and in combination, on depression symptoms in pregnant individuals. METHODS: The Alberta Pregnancy Outcomes and Nutrition cohort study included pregnant participants and their children from Calgary and Edmonton, Canada. Iron biomarkers (serum ferritin [SF], soluble transferrin receptor, and hepcidin) were measured via immunoassays and vitamin D [25-hydroxyvitamin D3 (25(OH)D3) and 3-epi-25-hydoxyvitamin D3 (3-epi-25(OH)D3)] metabolites were quantifed using liquid chromatography with tandem mass spectroscopy. Four categories of maternal iron and vitamin D status during the second trimester were conceptualized using concentrations of SF and total 25-hydoxyvitamin D [25(OH)D], respectively. Maternal Edinburgh Postnatal Depression Scale (EPDS) scores during the third trimester (n = 1920) and 3 mo postpartum (n = 1822) were obtained. RESULTS: Concentrations of maternal 25(OH)D3, 3-epi-25(OH)D3, and the ratio of both metabolites were significantly higher during the second trimester compared with their status at 3 mo postpartum. Higher second trimester maternal concentrations of SF (ß: -0.8; 95% confidence interval [CI]: -1.5, -0.01), hepcidin (ß: -0.5; 95% CI: -0.9, -0.2), and 25(OH)D3 (ß: -0.01; 95% CI: -0.02, -0.004) predicted lower maternal EPDS scores during the third trimester. Pregnant individuals with a low iron (SF <15 µg/L) and replete vitamin D (25(OH)D ≥75 nmol/L) (ß: 1.1; 95% CI: 0.03, 2.1) or low iron (SF <15 µg/L) and vitamin D (25(OH)D <75 nmol/L) (ß: 2.2; 95% CI: 0.3, 4.2) status during midpregnancy had higher third trimester EPDS scores compared with those that were replete in both micronutrients. CONCLUSIONS: A higher midpregnancy maternal iron and vitamin D status, independently or in combination, predicted fewer maternal depression symptoms in the third trimester. Concentrations of maternal 25(OH)D3 and 3-epi-25(OH)D3 may be lower in the postpartum period compared with midpregnancy.

Knowledge gaps in understanding the metabolic and clinical effects of excess folates/folic acid: a summary, and perspectives, from an NIH workshop.

Folate, an essential nutrient found naturally in foods in a reduced form, is present in dietary supplements and fortified foods in an oxidized synthetic form (folic acid). There is widespread agreement that maintaining adequate folate status is critical to prevent diseases due to folate inadequacy (e.g., anemia, birth defects, and cancer). However, there are concerns of potential adverse effects of excess folic acid intake and/or elevated folate status, with the original concern focused on exacerbation of clinical effects of vitamin B-12 deficiency and its role in neurocognitive health. More recently, animal and observational studies have suggested potential adverse effects on cancer risk, birth outcomes, and other diseases. Observations indicating adverse effects from excess folic acid intake, elevated folate status, and unmetabolized folic acid (UMFA) remain inconclusive; the data do not provide the evidence needed to affect public health recommendations. Moreover, strong biological and mechanistic premises connecting elevated folic acid intake, UMFA, and/or high folate status to adverse health outcomes are lacking. However, the body of evidence on potential adverse health outcomes indicates the need for comprehensive research to clarify these issues and bridge knowledge gaps. Three key research questions encompass the additional research needed to establish whether high folic acid or total folate intake contributes to disease risk. 1) Does UMFA affect biological pathways leading to adverse health effects? 2) Does elevated folate status resulting from any form of folate intake affect vitamin B-12 function and its roles in sustaining health? 3) Does elevated folate intake, regardless of form, affect biological pathways leading to adverse health effects other than those linked to vitamin B-12 function? This article summarizes the proceedings of an August 2019 NIH expert workshop focused on addressing these research areas.

Serum Betaine and Dimethylglycine Are Higher in South Asian Compared with European Pregnant Women in Canada, with Betaine and Total Homocysteine Inversely Associated in Early and Midpregnancy, Independent of Ethnicity.

BACKGROUND: As a methyl donor required in the folate-vitamin B-12 independent remethylation of total homocysteine (tHcy) to methionine, betaine is critical for fetal development. Pregnant South Asian women living in Canada had a higher reported prevalence of low vitamin B-12 status compared with Europeans; betaine concentrations in this population are unknown. OBJECTIVES: We aimed to compare serum betaine concentrations between South Asian and European pregnant women, and to determine the relation between betaine and tHcy concentrations in early pregnancy. METHODS: A retrospective cohort study was conducted using biobanked serum samples of 723 apparently healthy pregnant women of South Asian (50%) and European ethnicity residing in British Columbia, Canada. Betaine, dimethylglycine (DMG), tHcy, and related metabolites were quantified in samples collected in the first (8-13 weeks of gestation) and second (14-20 weeks of gestation) trimesters. The relation between betaine and tHcy concentrations was assessed using a generalized regression model adjusted for weeks of gestation, ethnicity, prepregnancy BMI, maternal age, neonatal sex, parity, total vitamin B-12, folate, pyridoxal 5'-phosphate, and methionine concentrations. RESULTS: Median serum concentrations of betaine and its metabolite DMG were higher in South Asian women in the first (19.8 [IQR: 16.3-25.0] and 1.55 [IQR: 1.30-1.96] $\mu {\rm mol/L} $, respectively) and second trimesters (16.1 [IQR: 12.9-19.8] and 1.42 [IQR: 1.14-1.81] $\mu {\rm mol/L} $, respectively) compared with European women (17.6 [IQR: 13.7-22.6] and 1.38 [IQR: 1.12-1.77] $\mu {\rm mol/L} $, respectively) and (12.9 [IQR: 10.6-16.7] and 1.19 [IQR: 0.97-1.52] $\mu {\rm mol/L} $, respectively; all P values < 0.0001). Betaine was inversely associated with tHcy concentration (ß = -0.0208; 95% CI: -0.0341, -0.00742; P = 0.002). Additionally, total vitamin B-12 was associated with tHcy concentration (ß = -0.0312; 95% CI: -0.0401, -0.0224), after adjusting for confounding factors. CONCLUSIONS: Pregnant South Asian women residing in Canada had higher betaine and DMG concentrations, compared with women of European ethnicity, while betaine and total vitamin B-12 predicted tHcy independent of ethnicity. Our results emphasize the role of betaine, as methyl donor, in the remethylation of tHcy in a folate-replete population.

Maternal Plasma Pyridoxal 5'-Phosphate Concentration Is Inversely Associated with Plasma Cystathionine Concentration across All Trimesters in Healthy Pregnant Women.

BACKGROUND: Vitamin B-6 (B-6), in the form of pyridoxal 5'phosphate (PLP), is critical for one-carbon metabolism reactions and cellular function. Plasma PLP concentration decreases throughout pregnancy, but the functional consequences of this have not been studied. Plasma cystathionine is a sensitive indicator of suboptimal B-6 status in healthy adults. OBJECTIVES: The aim of this study was to determine the relation between plasma PLP and cystathionine concentrations, and to assess longitudinal changes in plasma concentrations of metabolites of one-carbon metabolism, including total homocysteine (tHcy), cysteine, methionine, glycine, serine, and glutathione, over the course of pregnancy. DESIGN: This was a prospective cohort study of 186 healthy Brazilian pregnant women (20-40 y). Plasma PLP and metabolite concentrations were quantified in fasting maternal blood samples collected between 5-13, 20-26, and 30-36 weeks of gestation. Linear mixed regression models were used to determine the association of 1) first-trimester PLP tertiles, and 2) the variation of PLP concentration throughout pregnancy, with related metabolite concentrations across weeks of gestation. RESULTS: Median (IQR) PLP concentration decreased from 36.2 (29.2-44.5) to 21.0 (15.9-26.0) to 16.8 (12.9-21.4) nmol/L in the first, second, and third trimester, respectively, whereas cystathionine concentration increased from 63.2 (49.7-78.9) to 122 (98.0-167) to 143 (114-193) nmol/L, respectively (both P < 0.001). The variation of PLP throughout pregnancy was inversely associated with cystathionine concentration across weeks of gestation, after adjusting for confounding factors; ß (95% CI) = -0.387 (-0.752, -0.219), P = 0.04. This association significantly differed by trimester and was strongest in the third trimester. Plasma concentrations of glycine, serine, methionine, cysteine, and tHcy decreased, and that of glutathione increased, between the first and second trimesters (all P < 0.05). CONCLUSIONS: The variation of PLP concentration predicted cystathionine concentration throughout pregnancy. Increases in plasma cystathionine across trimesters may reflect maternal intracellular B-6 deficiency.

Periconceptional intake of folic acid among low-risk women in Canada: summary of a workshop aiming to align prenatal folic acid supplement composition with current expert guidelines.

The Government of Canada and the Society of Obstetricians and Gynaecologists of Canada both recommend a daily multivitamin supplement containing 400 µg folic acid (FA) for the primary prevention of neural tube defects among low-risk women from before conception and throughout lactation. Prenatal supplements marketed and prescribed in Canada typically exceed the recommended dose, usually providing ≥1000 µg FA/d. This high daily dose, coupled with staple-food FA fortification, has resulted in the observation of very high blood folate concentrations among reproductive-aged women consuming FA-containing supplements. The long-term consequences of high folate status on fetal development are unknown; however, evidence from animal studies and some human epidemiologic data suggest potential adverse consequences. To address this issue, a workshop was convened with the overall goal to identify challenges and solutions to aligning supplemental FA intakes with current evidence-based recommendations. Thirty-eight stakeholders from academia, industry, government, and health professional groups participated. Group discussions facilitated the identification and prioritization of 5 key challenges for which solutions and implementation strategies were proposed. The 5 themes encompassed clarity and harmonization of evidence-based guidelines, reformulation or relabeling of FA-containing supplements, access to FA for all women, knowledge dissemination strategies and education of the public and health care professionals, and attitude change to overcome the perception of "more is better." A combination of the proposed implementation strategies involving all key stakeholders and directed to health care professionals and the public may enable a sustainable change to align FA intake during the periconceptional period with evidence-based recommendations.

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 (ß = 0.252, P = 0.012) and inversely associated with serum n-6-to-n-3 (ω-6-to-ω-3) FA ratio (ß = -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.

Folic acid fortified milk increases blood folate to concentrations associated with a very low risk of neural tube defects in Singaporean women of childbearing age.

BACKGROUND AND OBJECTIVES: Folic acid (400 µg/d) taken during the periconceptional period reduces neural tube defect (NTD) risk by >75%. Achieving red cell folate (RCF) or plasma folate (PF) >905 nmol/L and >35 nmol/L, respectively, has been associated with a low risk of NTDs. We determined whether daily consumption of folic acid fortified milk increases blood folate concentrations to levels associated with a low risk of NTDs in Singaporean women of childbearing age. METHODS AND STUDY DESIGN: In this double-blind placebo-controlled trial, 70 non-pregnant women (21-35 y) were randomly assigned to receive fortified milk (FM) powder providing 400 µg folic acid per day or unfortified placebo milk (PM) powder for 12 weeks. Blood samples were collected at baseline and at 6 and 12 weeks. RESULTS: At 12 weeks, mean (95% CI) RCF and PF concentrations were 376 (240, 512) and 39 (26, 51) nmol/L higher in the FM group compared with the PM group (p<0.001). Of the women receiving FM, 71% (n=25) and 86% (n=30) achieved a RCF and PF associated with a very low risk of NTDs, respectively. CONCLUSION: Folic acid fortified milk increased blood folate concentrations in women of childbearing age to levels associated with a reduced risk of an NTD-affected pregnancy.

Genetic hemoglobin disorders rather than iron deficiency are a major predictor of hemoglobin concentration in women of reproductive age in rural prey Veng, Cambodia.

BACKGROUND: Anemia is common in Cambodian women. Potential causes include micronutrient deficiencies, genetic hemoglobin disorders, inflammation, and disease. OBJECTIVES: We aimed to investigate factors associated with anemia (low hemoglobin concentration) in rural Cambodian women (18-45 y) and to investigate the relations between hemoglobin disorders and other iron biomarkers. METHODS: Blood samples were obtained from 450 women. A complete blood count was conducted, and serum and plasma were analyzed for ferritin, soluble transferrin receptor (sTfR), folate, vitamin B-12, retinol binding protein (RBP), C-reactive protein (CRP), and α1 acid glycoprotein (AGP). Hemoglobin electrophoresis and multiplex polymerase chain reaction were used to determine the prevalence and type of genetic hemoglobin disorders. RESULTS: Overall, 54% of women had a genetic hemoglobin disorder, which included 25 different genotypes (most commonly, hemoglobin E variants and α(3.7)-thalassemia). Of the 420 nonpregnant women, 29.5% had anemia (hemoglobin <120 g/L), 2% had depleted iron stores (ferritin <15 µg/L), 19% had tissue iron deficiency (sTfR >8.3 mg/L), <3% had folate deficiency (<3 µg/L), and 1% had vitamin B-12 deficiency (<150 pmol/L). Prevalences of iron deficiency anemia (IDA) were 14.2% and 1.5% in those with and without hemoglobin disorders, respectively. There was no biochemical evidence of vitamin A deficiency (RBP <0.7 µmol/L). Acute and chronic inflammation were prevalent among 8% (CRP >5 mg/L) and 26% (AGP >1 g/L) of nonpregnant women, respectively. By using an adjusted linear regression model, the strongest predictors of hemoglobin concentration were hemoglobin E homozygous disorder and pregnancy status. Other predictors were 2 other heterozygous traits (hemoglobin E and Constant Spring), parity, RBP, log ferritin, and vitamin B-12. CONCLUSIONS: Multiple biomarkers for anemia and iron deficiency were significantly influenced by the presence of hemoglobin disorders, hence reducing their diagnostic sensitivity. Further investigation of the unexpectedly low prevalence of IDA in Cambodian women is warranted.

Metabolite profile analysis reveals functional effects of 28-day vitamin B-6 restriction on one-carbon metabolism and tryptophan catabolic pathways in healthy men and women.

Suboptimal vitamin B-6 status, as reflected by low plasma pyridoxal 5'-phosphate (PLP) concentration, is associated with increased risk of vascular disease. PLP plays many roles, including in one-carbon metabolism for the acquisition and transfer of carbon units and in the transsulfuration pathway. PLP also serves as a coenzyme in the catabolism of tryptophan. We hypothesize that the pattern of these metabolites can provide information reflecting the functional impact of marginal vitamin B-6 deficiency. We report here the concentration of major constituents of one-carbon metabolic processes and the tryptophan catabolic pathway in plasma from 23 healthy men and women before and after a 28-d controlled dietary vitamin B-6 restriction (<0.35 mg/d). liquid chromatography-tandem mass spectrometry analysis of the compounds relevant to one-carbon metabolism showed that vitamin B-6 restriction yielded increased cystathionine (53% pre- and 76% postprandial; P < 0.0001) and serine (12% preprandial; P < 0.05), and lower creatine (40% pre- and postprandial; P < 0.0001), creatinine (9% postprandial; P < 0.05), and dimethylglycine (16% postprandial; P < 0.05) relative to the vitamin B-6-adequate state. In the tryptophan pathway, vitamin B-6 restriction yielded lower kynurenic acid (22% pre- and 20% postprandial; P < 0.01) and higher 3-hydroxykynurenine (39% pre- and 34% postprandial; P < 0.01). Multivariate ANOVA analysis showed a significant global effect of vitamin B-6 restriction and multilevel partial least squares-discriminant analysis supported this conclusion. Thus, plasma concentrations of creatine, cystathionine, kynurenic acid, and 3-hydroxykynurenine jointly reveal effects of vitamin B-6 restriction on the profiles of one-carbon and tryptophan metabolites and serve as biomarkers of functional effects of marginal vitamin B-6 deficiency.

Metabolomic analysis reveals extended metabolic consequences of marginal vitamin B-6 deficiency in healthy human subjects.

Marginal deficiency of vitamin B-6 is common among segments of the population worldwide. Because pyridoxal 5'-phosphate (PLP) serves as a coenzyme in the metabolism of amino acids, carbohydrates, organic acids, and neurotransmitters, as well as in aspects of one-carbon metabolism, vitamin B-6 deficiency could have many effects. Healthy men and women (age: 20-40 y; n = 23) were fed a 2-day controlled, nutritionally adequate diet followed by a 28-day low-vitamin B-6 diet (<0.5 mg/d) to induce marginal deficiency, as reflected by a decline of plasma PLP from 52.6±14.1 (mean ± SD) to 21.5±4.6 nmol/L (P<0.0001) and increased cystathionine from 131±65 to 199±56 nmol/L (P<0.001). Fasting plasma samples obtained before and after vitamin B6 restriction were analyzed by (1)H-NMR with and without filtration and by targeted quantitative analysis by mass spectrometry (MS). Multilevel partial least squares-discriminant analysis and S-plots of NMR spectra showed that NMR is effective in classifying samples according to vitamin B-6 status and identified discriminating features. NMR spectral features of selected metabolites indicated that vitamin B-6 restriction significantly increased the ratios of glutamine/glutamate and 2-oxoglutarate/glutamate (P<0.001) and tended to increase concentrations of acetate, pyruvate, and trimethylamine-N-oxide (adjusted P<0.05). Tandem MS showed significantly greater plasma proline after vitamin B-6 restriction (adjusted P<0.05), but there were no effects on the profile of 14 other amino acids and 45 acylcarnitines. These findings demonstrate that marginal vitamin B-6 deficiency has widespread metabolic perturbations and illustrate the utility of metabolomics in evaluating complex effects of altered vitamin B-6 intake.

Moderate vitamin B-6 restriction does not alter postprandial methionine cycle rates of remethylation, transmethylation, and total transsulfuration but increases the fractional synthesis rate of cystathionine in healthy young men and women.

Methionine is the precursor for S-adenosylmethionine (SAM), the major 1-carbon donor involved in >100 transmethylation reactions. Homocysteine produced from SAM must be metabolized either by remethylation for recycling of methionine or transsulfuration to form cystathionine and then cysteine. Pyridoxal 5'-phosphate (PLP) serves as a coenzyme in enzymes involved in transsulfuration as well as for primary acquisition of 1-carbon units used for remethylation and other phases of 1-carbon metabolism. Because the intake of vitamin B-6 is frequently low in humans and metabolic consequences of inadequacy may be amplified in the postprandial state, we aimed to determine the effects of marginal vitamin B-6 deficiency on the postprandial rates of remethylation, transmethylation, overall transsulfuration, and cystathionine synthesis. Healthy, young adults (4 male, 5 female; 20-35 y) received a primed, constant infusion of [1-(13)C]methionine, [methyl-(2)H(3)]methionine, and [5,5,5-(2)H(3)]leucine to quantify in vivo kinetics at normal vitamin B-6 status and after a 28-d dietary vitamin B-6 restriction. Vitamin B-6 restriction lowered the plasma PLP concentration from 49 ± 4 nmol/L (mean ± SEM) to 19 ± 2 nmol/L (P < 0.0001). Mean remethylation, transsulfuration, and transmethylation rates did not change in response to vitamin B-6 restriction; however, the responses to vitamin B-6 restriction varied greatly among individuals. The plasma cystathionine concentration increased from 142 ± 8 to 236 ± 9 nmol/L (P < 0.001), whereas the fractional cystathionine synthesis rate increased by a mean of 12% in 8 of 9 participants. Interrelationships among plasma concentrations of glycine and cystathionine and kinetic results suggest that individual variability occurs in normal postprandial 1-carbon metabolism and in the response to vitamin B-6 restriction.

Vitamin B-6 restriction tends to reduce the red blood cell glutathione synthesis rate without affecting red blood cell or plasma glutathione concentrations in healthy men and women.

BACKGROUND: Glutathione plays various protective roles in the human body. Vitamin B-6 as pyridoxal-5'-phosphate (PLP) is required as the coenzyme in the formation of glutathione precursors. Despite this obligatory role of PLP, previous studies from this laboratory showed that vitamin B-6 deficiency caused elevated glutathione concentrations in rat liver and human plasma. OBJECTIVE: Our aim was to determine the effect of marginal vitamin B-6 deficiency (plasma PLP 20-30 nmol/L) on the rate of red blood cell (RBC) glutathione synthesis. DESIGN: We measured plasma and RBC glutathione concentrations and the fractional and absolute synthesis rates of RBC glutathione using the stable-isotope-labeled glutathione precursor [1,2-(13)C(2)]glycine in 13 healthy volunteers aged 21-39 y. RESULTS: Dietary vitamin B-6 restriction did not significantly affect the glutathione concentration in plasma (6.9 +/- 1.9 compared with 6.7 +/- 1.1 micromol/L) or RBCs (2068 +/- 50 compared with 2117 +/- 48 micromol/L). For RBC glutathione, the mean fractional synthesis rates were 54 +/- 5%/d and 43 +/- 4%/d (P = 0.10), and the absolute synthesis rates were 1116 +/- 100 and 916 +/- 92 micromol . L(-1) . d(-1) (P = 0.14) before and after vitamin B-6 restriction, respectively. CONCLUSIONS: Marginal vitamin B-6 deficiency tended to decrease mean RBC glutathione synthesis with no effect on RBC glutathione concentration, but the responses varied widely among individuals. Because the cysteine concentration in plasma and RBC did not change during vitamin B-6 restriction, we conclude that the effects of marginal vitamin B-6 deficiency on glutathione synthesis are not caused by altered precursor concentrations.

Moderate dietary vitamin B-6 restriction raises plasma glycine and cystathionine concentrations while minimally affecting the rates of glycine turnover and glycine cleavage in healthy men and women.

Glycine is a precursor of purines, protein, glutathione, and 1-carbon units as 5,10-methylenetetrahydrofolate. Glycine decarboxylation through the glycine cleavage system (GCS) and glycine-serine transformation by serine hydroxymethyltransferase (SHMT) require pyridoxal 5'-phosphate (PLP; active form of vitamin B-6) as a coenzyme. The intake of vitamin B-6 is frequently low in humans. Therefore, we determined the effects of vitamin B-6 restriction on whole-body glycine flux, the rate of glycine decarboxylation, glycine-to-serine conversion, use of glycine carbons in nucleoside synthesis, and other aspects of 1-carbon metabolism. We used a primed, constant infusion of [1,2-(13)C(2)]glycine and [5,5,5-(2)H(3)]leucine to quantify in vivo kinetics in healthy adults (7 males, 6 females; 20-39 y) of normal vitamin B-6 status or marginal vitamin B-6 deficiency. Vitamin B-6 restriction lowered the plasma PLP concentration from 55 +/- 4 nmol/L (mean +/- SEM) to 23 +/- 1 nmol/L (P < 0.0001), which is consistent with marginal deficiency, whereas the plasma glycine concentration increased (P < 0.01). SHMT-mediated conversion of glycine to serine increased from 182 +/- 7 to 205 +/- 9 micromol x kg(-1) x h(-1) (P < 0.05), but serine production using a GCS-derived 1-carbon unit (93 +/- 9 vs. 91 +/- 6 micromol x kg(-1) x h(-1)) and glycine cleavage (163 +/- 11 vs. 151 +/- 8 micromol x kg(-1) x h(-1)) were not changed by vitamin B-6 restriction. The GCS produced 1-carbon units at a rate (approximately 140-170 micromol x kg(-1) x h(-1)) that greatly exceeds the demand for remethylation and transmethylation processes (approximately 4-7 micromol x kg(-1) x h(-1)). We conclude that the in vivo GCS and SHMT reactions are quite resilient to the effects of marginal vitamin B-6 deficiency, presumably through a compensatory effect of increasing substrate concentration.

Supplementation with a multivitamin containing 800 microg of folic acid shortens the time to reach the preventive red blood cell folate concentration in healthy women.

BACKGROUND: The lowest risk of having a child with a neural tube defect (NTD) was related to red blood cell (RBC) folate concentrations of >906 nmol/L. For NTD prevention, it is recommended that women use periconceptional supplementation of 400 microg/day folic acid. Using this dose previous studies indicate that RBC folate >906 nmol/L was not reached within four weeks of supplementation. OBJECTIVE: The effectiveness of a multivitamin/multimineral supplement containing 800 microg folic acid (verum) was evaluated using RBC folate concentration exceeding 906 nmol/L as primary endpoint. In addition, the time frame of achieving the threshold level was established as well as the effect of supplementation of other B vitamins on folate metabolism. SUBJECTS AND METHODS: 46 healthy females received 800 microg/day of folic acid or placebo for 16 weeks. Blood samples were collected in four-week intervals. Plasma and RBC folate were measured with the microbiological method. RESULTS: Mean (+/-SED) RBC folate increased over time to 1430+/-53 nmol/L, but did not reach a steady state after 16 weeks of intervention. Mean time to reach the target level was 4.2 +/- 3.5 weeks in the verum group. Intake of verum also led to an increase over time of plasma folate. CONCLUSIONS: Preventive RBC folate concentration of more than 906 nmol/L can be reached within four weeks of supplementation with daily intake of 800 microg folic acid. With respect to NTD prevention, we suggest the re-evaluation of the current recommendation of folic acid supplementation.

Calculation of red blood cell folate steady state conditions and elimination kinetics after daily supplementation with various folate forms and doses in women of childbearing age.

BACKGROUND: A maternal red blood cell (RBC) folate concentration > 906 nmol/L is thought to be optimal for lowering the risk of neural tube defects (NTDs) in pregnancy. Whereas the appearance of folate in RBCs has been followed during folic acid supplementation, data on elimination kinetics are not yet available. OBJECTIVE: The aim of our investigation was to estimate the steady state conditions and elimination kinetics of folate in RBCs. DESIGN: Data from 2 randomized, placebo-controlled, double-blind intervention trials were used for kinetic modeling. These studies were performed to investigate the appearance of folate in RBCs in healthy women of childbearing age after different supplementation strategies (study 1: n = 69; 400 microg folic acid/d and 416 microg [6S]-5-methyltetrahydrofolate/d for 24 wk; study 2: n = 21; 800 microg folic acid/d for 16 wk). RESULTS: For RBC folate concentrations, steady state conditions were not reached after 24 (study 1) and 16 (study 2) wk of folate supplementation. However, with the use of these data, we calculated the biological half-life (t(1/2)) of RBC folate to be approximately 8 wk. With the application of pharmacokinetic principles, steady state conditions for RBC folate should be reached after 40 wk (t(1/2) x 5). CONCLUSION: With the use of pharmacokinetic principles, the appearance and elimination kinetics of RBC folate can be calculated on the basis of this t(1/2) value.

Red blood cell folate concentrations increase more after supplementation with [6S]-5-methyltetrahydrofolate than with folic acid in women of childbearing age.

BACKGROUND: For the primary prevention of neural tube defects (NTDs), public health authorities recommend women of childbearing age to take 400 mug folic acid/d 4 wk before conception and during the first trimester. The biologically active derivate [6S]-5-methyltetrahydrofolate ([6S]-5-MTHF) could be an alternative to folic acid. OBJECTIVE: We investigated the effect of supplementation with [6S]-5-MTHF compared with that of folic acid on red blood cell folate concentration, an indicator of folate status. DESIGN: The study was designed as a double-blind, randomized, placebo-controlled intervention trial. Healthy women (n = 144) aged 19-33 y received 400 microg folic acid, the equimolar amount of [6S]-5-MTHF (416 microg), 208 microg [6S]-5-MTHF, or placebo as a daily supplement for 24 wk. Red blood cell and plasma folate concentrations were measured at baseline and at 4-wk intervals. RESULTS: The increase in red blood cell folate over time was significantly higher in the group receiving 416 microg [6S]-5-MTHF/d than in the groups receiving 400 microg folic acid/d or 208 microg [6S]-5-MTHF/d (P < 0.001). No plateau was reached in red blood cell folate concentration in the 3 treatment groups during 24 wk of intervention; however, plasma folate plateaued after 12 wk. CONCLUSIONS: We showed that administration of [6S]-5-MTHF is more effective than is folic acid supplementation at improving folate status. In addition, the study indicates that the recommended period for preconceptional folic acid supplementation should be extended to >4 wk for maximal prevention of NTDs based on folate concentrations. [6S]-5-MTHF might be an efficient and safe alternative to folic acid.

Supplementation with [6S]-5-methyltetrahydrofolate or folic acid equally reduces plasma total homocysteine concentrations in healthy women.

BACKGROUND: Increased plasma total homocysteine (tHcy) is a risk factor for vascular disease and adverse pregnancy outcomes. Health authorities recommend periconceptional supplementation with 400 micro g folic acid to prevent neural tube defects. Several countries have implemented food fortification with folic acid. However, excessive intake of folic acid could mask an undiagnosed vitamin B-12 deficiency. The biologically active [6S]-5-methyltetrahydrofolate ([6S]-5-MTHF) may be an alternative to folic acid because it is unlikely to mask vitamin B-12 deficiency symptoms. OBJECTIVE: We compared the tHcy-lowering potential of 2 dosages of [6S]-5-MTHF with that of 400 micro g folic acid during 24 wk of supplementation. DESIGN: In this double-blind, randomized, controlled intervention trial, 144 female participants were supplemented daily with 400 micro g folic acid, 416 micro g [6S]-5-MTHF, 208 micro g [6S]-5-MTHF, or placebo. Concentrations of tHcy and plasma folate were measured at baseline and at 4-wk intervals. RESULTS: After supplementation, there was a significant interaction between time and treatment with respect to changes in tHcy and plasma folate (both P < 0.001 by two-factor repeated-measures analysis of variance). The decrease in tHcy did not differ significantly between the 3 supplemented groups (P > 0.05; Tukey's post hoc test). The increase in plasma folate in the group receiving 208 micro g [6S]-5-MTHF was significantly lower than that in the groups receiving 400 micro g folic acid (P < 0.001) or 416 micro g [6S]-5-MTHF (P < 0.05). CONCLUSIONS: [6S]-5-MTHF was shown to be an adequate alternative to folic acid in reducing tHcy concentrations. Supplementation with 416 micro g [6S]-5-MTHF was no more effective than that with 208 micro g [6S]-5-MTHF.