Women Taking a Folic Acid Supplement in Countries with Mandatory Food Fortification Programs May Be Exceeding the Upper Tolerable Limit of Folic Acid: A Systematic Review

Red blood cell folate and benign prostatic hyperplasia: results from the NHANES 2001-2008

BACKGROUND

Benign prostatic hyperplasia (BPH) affects 30% of men worldwide, folate is essential for life. However, few studies have investigated the relationship between folate levels and BPH. The present study aims to explore the relationship between red blood cell (RBC) folate, a better indicator of long-term folate intake, and BPH in United States (US) men.

METHODS

We used statistics from four cycles of the "National Health and Nutrition Examination Survey" (NHANES2001-2008), RBC folate data come from laboratory data and BPH date come from questionnaire data. A multivariate conditional logistic regression model and subgroup analysis were using to assess the association between RBC folate and BPH.

RESULTS

647 males from four survey cycles in the NHANES2001-2008, of which, 574 men (88.7%) had BPH. After adjusting for potential confounders, a considerable correlation was observed between RBC folate and BPH; With the first quintiles of RBC folate as the reference, multivariable-adjusted odds ratios (ORs) and confidence intervals (95% CIs) of the second, third, fourth, and the highest quintiles were 1.19 (0.58 ∼ 2.44), 1.39 (0.65 ∼ 2.97), 2.27 (0.96 ∼ 5.39), 2.26 (1.35 ∼ 3.76) and 5.37 (1.85 ∼ 15.59), respectively.

CONCLUSIONS

Individuals with high levels of RBC folate were associated with an increased risk of self-reported benign prostatic hyperplasia of US men.

Gestational diabetes mellitus is associated with distinct folate-related metabolites in early and mid-pregnancy: A prospective cohort study

AIMS

This study aimed to evaluate the association between gestational diabetes mellitus (GDM) and circulating folate metabolites, folic acid (FA) intake, and the methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) genotype.

MATERIALS AND METHODS

A prospective pregnancy cohort study was conducted in Beijing, China, from 2022 to 2023. Circulating folate metabolites, including red blood cell (RBC) 5-methyltetrahydrofolate (5-MTHF), 5, 10-methylene-tetrahydrofolate (5,10-CH2-THF), 5- formyltetrahydrofolate (5-CHO-THF), and unmetabolised folic acid (UMFA), and plasma homocysteine (HCY), 5-MTHF, and methylmalonic acid (MMA), were determined at 6-17 weeks and 20-26 weeks of gestation. FA intake and the MTHFR and MTRR genotype were also examined. GDM was diagnosed between 24 and 28 weeks of pregnancy by a 75-g oral glucose tolerance test (OGTT). The association between the folate status and GDM was ascertained using multivariate generalised linear models, logistic regression models, and restricted cubic spline regression, adjusting for potential confounders.

RESULTS

The study included 2032 pregnant women, of whom 392 (19.29%) developed GDM. UMFA above the 75th percentile (≥P75) [adjusted OR (aOR) (95% confidence interval [CI]) = 1.36 (1.01-1.84)], UMFA ≥ P90 [aOR (95% CI) = 1.82 (1.23-2.69)], and HCY ≥ P75 [aOR (95% CI) = 1.40 (1.04-1.88)] in early pregnancy, and RBC 5-MTHF [aOR (95% CI) = 1.48 (1.10-2.00)], RBC 5,10-CH2-THF [aOR (95% CI) = 1.55 (1.15-2.10)], and plasma 5-MTHF [aOR (95% CI) = 1.36 (1.00-1.86)] in mid-pregnancy ≥ P75 are associated with GDM. Higher UMFA levels in early pregnancy show positive associations with the 1-h and 2-h glucose levels during the OGTT, and higher HCY levels are associated with increased fasting glucose levels during the OGTT. In comparison, RBC 5- MTHF and 5,10-CH2-THF, and plasma 5- MTHF in mid-pregnancy are positively associated with the 1-h glucose level (p < 0.05). The MTHFR and MTRR genotype and FA intake are not associated with GDM.

CONCLUSIONS

Elevated levels of UMFA and HCY during early pregnancy, along with elevated RBC 5-MTHF and 5,10-CH2-THF and plasma 5-MTHF during mid-pregnancy, are associated with GDM. These findings indicate distinct connections between different folate metabolites and the occurrence of GDM.

Supplementation with (6S)-5-methyltetrahydrofolic acid appears as effective as folic acid in maintaining maternal folate status while reducing unmetabolised folic acid in maternal plasma: a randomised trial of pregnant women in Canada

Folic acid supplementation is recommended during pregnancy to support healthy fetal development; (6S)-5-methyltetrahydrofolic acid ((6S)-5-MTHF) is available in some commercial prenatal vitamins as an alternative to folic acid, but its effect on blood folate status during pregnancy is unknown. To address this, we randomised sixty pregnant individuals at 8-21 weeks' gestation to 0·6 mg/d folic acid or (6S)-5-MTHF × 16 weeks. Fasting blood specimens were collected at baseline and after 16 weeks (endline). Erythrocyte and serum folate were quantified via microbiological assay (as globally recommended) and plasma unmetabolised folic acid (UMFA) via LC-MS/MS. Differences in biochemical folate markers between groups were explored using multivariable linear/quantile regression, adjusting for baseline concentrations, dietary folate intake and gestational weeks. At endline (n 54), the mean values and standard deviations (or median, inter-quartile range) of erythrocyte folate, serum folate and plasma UMFA (nmol/l) in those supplemented with (6S)-5-MTHF v. folic acid, respectively, were 1826 (sd 471) and 1998 (sd 421); 70 (sd 13) and 78 (sd 17); 0·5 (0·4, 0·8) and 1·3 (0·9, 2·1). In regression analyses, erythrocyte and serum folate did not differ by treatment group; however, concentrations of plasma UMFA in pregnancy were 0·6 nmol/l higher (95 % CI 0·2, 1·1) in those supplementing with folic acid as compared with (6S)-5-MTHF. In conclusion, supplementation with (6S)-5-MTHF may reduce plasma UMFA by ∼50 % as compared with supplementation with folic acid, the biological relevance of which is unclear. As folate is currently available for purchase in both forms, the impact of circulating maternal UMFA on perinatal outcomes needs to be determined.

Dietary supplements, guideline alignment and biochemical nutrient status in pregnancy: Findings from the Queensland Family Cohort pilot study

In high-income nations, multiple micronutrient (MMN) supplementation during pregnancy is a common practice. We aimed to describe maternal characteristics associated with supplement use and daily dose of supplemental nutrients consumed in pregnancy, and whether guideline alignment and nutrient status are related to supplement use. The Queensland Family Cohort is a prospective, Australian observational longitudinal study. Maternal characteristics, nutrient intake from food and supplements, and biochemical nutrient status were assessed in the second trimester (n = 127). Supplement use was reported by 89% of participants, of whom 91% reported taking an MMN supplement. Participants who received private obstetric care, had private health insurance and had greater alignment to meat/vegetarian alternatives recommendations were more likely to report MMN supplement use. Private obstetric care and general practitioner shared care were associated with higher daily dose of supplemental nutrients consumed compared with midwifery group practice. There was high reliance on supplements to meet nutrient reference values for folate, iodine and iron, but only plasma folate concentrations were higher in MMN supplement versus nonsupplement users. Exceeding the upper level of intake for folic acid and iron was more likely among combined MMN and individual supplement/s users, and associated with higher plasma concentrations of the respective nutrients. Given the low alignment with food group recommendations and potential risks associated with high MMN supplement use, whole food diets should be emphasized. This study confirms the need to define effective strategies for optimizing nutrient intake in pregnancy, especially among those most vulnerable where MMN supplement use may be appropriate.

Parental folic acid deficiency delays neurobehavioral development in rat offspring by inhibiting the differentiation of neural stem cells into neurons

Maternal folate status during pregnancy is associated with the neurodevelopment of offspring; however, study results on the association between paternal folate status and offspring neurodevelopment are inconsistent. This study aimed to explore whether parental folic acid deficiency affects the neurobehavioral development of offspring by affecting the differentiation of neural stem cells (NSCs) into neurons. In the present study, the offspring were divided into four groups: parental folic acid deficient group (D-D), maternal folic acid deficient and paternal folic acid normal group (D-N), maternal folic acid normal and paternal folic acid deficient group (N-D), and parental folic acid normal group (N-N). For in vivo study, neurobehavioral indexes, and neuron-specific nuclear protein (NeuN) and glial fibrillary acidic protein (GFAP) expression in the brain hippocampus and cerebral cortex of offspring were measured at different time points. For in vitro study, NSCs were cultured from the hippocampus and striatum, and neuronal and astrocytic differentiation were measured. The results demonstrated that parental folic acid deficiency decreased the brain folate level in offspring, delayed early sensory-motor reflex development, impaired spatial learning and memory ability in adolescence and adulthood, decreased differentiation of NSCs into neurons and increased differentiation of NSCs into astrocytes in vivo and in vitro. These impacts on the neurodevelopment of offspring were most pronounced in D-D group, followed by D-N group and N-D group. In conclusion, parental folic acid deficiency inhibits the neurobehavioral development of offspring, possibly by inhibiting the differentiation of NSCs into neurons.

Uncovering the Hidden Dangers and Molecular Mechanisms of Excess Folate: A Narrative Review

This review delves into the intricate relationship between excess folate (vitamin B9) intake, especially its synthetic form, namely, folic acid, and its implications on health and disease. While folate plays a pivotal role in the one-carbon cycle, which is essential for DNA synthesis, repair, and methylation, concerns arise about its excessive intake. The literature underscores potential deleterious effects, such as an increased risk of carcinogenesis; disruption in DNA methylation; and impacts on embryogenesis, pregnancy outcomes, neurodevelopment, and disease risk. Notably, these consequences stretch beyond the immediate effects, potentially influencing future generations through epigenetic reprogramming. The molecular mechanisms underlying these effects were examined, including altered one-carbon metabolism, the accumulation of unmetabolized folic acid, vitamin-B12-dependent mechanisms, altered methylation patterns, and interactions with critical receptors and signaling pathways. Furthermore, differences in the effects and mechanisms mediated by folic acid compared with natural folate are highlighted. Given the widespread folic acid supplementation, it is imperative to further research its optimal intake levels and the molecular pathways impacted by its excessive intake, ensuring the health and well-being of the global population.

Vitamins and Human Health: Systematic Reviews and Original Research

Vitamins are a group of organic compounds essential to physiological functions in the body [...].

Does maternal genetic liability to folate deficiency influence the risk of antiseizure medication-associated language impairment and autistic traits in children of women with epilepsy?

BACKGROUND

Prenatal exposure to antiseizure medication (ASM) may lead to low plasma folate concentrations and is associated with impaired neurodevelopment.

OBJECTIVE

To examine whether maternal genetic liability to folate deficiency interacts with ASM-associated risk of language impairment and autistic traits in children of women with epilepsy.

METHODS

We included children of women with and without epilepsy and with available genetic data enrolled in the Norwegian Mother, Father, and Child Cohort Study (MoBa). Information on ASM use, folic acid supplement use and dose, dietary folate intake, child autistic traits, and child language impairment was obtained from parent-reported questionnaires. Using logistic regression, we examined the interaction between prenatal ASM exposure and maternal genetic liability to folate deficiency expressed as polygenic risk score (PRS) of low folate concentrations or maternal rs1801133 genotype (CC or CT/TT) on risk of language impairment or autistic traits.

RESULTS

We included 96 children of women with ASM-treated epilepsy, 131 children of women with ASM-untreated epilepsy, and 37,249 children of women without epilepsy. The PRS of low folate concentrations or the maternal rs1801133 genotype did not interact with the ASM-associated risk of language impairment or autistic traits in ASM-exposed children of women with epilepsy compared to ASM-unexposed children aged 1.5-8 years. ASM-exposed children had increased risk of adverse neurodevelopment regardless of maternal rs1801133 genotype (adjusted odds ratio (aOR) for language impairment age 8 years was 2.88 (95% confidence interval (CI) 1.00-8.26) if CC and aOR 2.88 (CI 1.10-7.53) if CT/TT genotypes). In children of women without epilepsy aged 3 years, those with maternal rs1801133 CT/TT compared to CC genotype had increased risk of language impairment (aOR 1.18, CI 1.05-1.34).

CONCLUSIONS

In this cohort of pregnant women reporting widespread use of folic acid supplements, maternal genetic liability to folate deficiency did not significantly influence the ASM-associated risk of impaired neurodevelopment.

Elevated Maternal Folate Status and Changes in Maternal Prolactin, Placental Lactogen and Placental Growth Hormone Following Folic Acid Food Fortification: Evidence from Two Prospective Pregnancy Cohorts

Folic acid (FA) food fortification in Australia has resulted in a higher-than-expected intake of FA during pregnancy. High FA intake is associated with increased insulin resistance and gestational diabetes. We aimed to establish whether maternal one-carbon metabolism and hormones that regulate glucose homeostasis change in healthy pregnancies post-FA food fortification. Circulating folate, B12, homocysteine, prolactin (PRL), human placental lactogen (hPL) and placental growth hormone (GH2) were measured in early pregnancy maternal blood in women with uncomplicated pregnancies prior to (SCOPE: N = 604) and post (STOP: N = 711)-FA food fortification. FA food fortification resulted in 63% higher maternal folate. STOP women had lower hPL (33%) and GH2 (43%) after 10 weeks of gestation, but they had higher PRL (29%) and hPL (28%) after 16 weeks. FA supplementation during pregnancy increased maternal folate and reduced homocysteine but only in the SCOPE group, and it was associated with 54% higher PRL in SCOPE but 28% lower PRL in STOP. FA food fortification increased maternal folate status, but supplements no longer had an effect, thereby calling into question their utility. An altered secretion of hormones that regulate glucose homeostasis in pregnancy could place women post-fortification at an increased risk of insulin resistance and gestational diabetes, particularly for older women and those with obesity.

Higher Concentrations of Folic Acid Cause Oxidative Stress, Acute Cytotoxicity, and Long-Term Fibrogenic Changes in Kidney Epithelial Cells

Kidney fibrosis is a common step during chronic kidney disease (CKD), and its incidence has been increasing worldwide. Aberrant recovery after repeated acute kidney injury leads to fibrosis. The mechanism of fibrogenic changes in the kidney is not fully understood. Folic acid-induced kidney fibrosis in mice is an established in vivo model to study kidney fibrosis, but the mechanism is poorly understood. Moreover, the effect of higher concentrations of folic acid on kidney epithelial cells in vitro has not yet been studied. Oxidative stress is a common property of nephrotoxicants. Therefore, this study evaluated the role of folic acid-induced oxidative stress in fibrogenic changes by using the in vitro renal proximal tubular epithelial cell culture model. To obtain comprehensive and robust data, three different cell lines derived from human and mouse kidney epithelium were treated with higher concentrations of folic acid for both acute and long-term durations, and the effects were determined at the cellular and molecular levels. The result of cell viability by the MTT assay and the measurement of reactive oxygen species (ROS) levels by the DCF assay revealed that folic acid caused cytotoxicity and increased levels of ROS in acute exposure. The cotreatment with antioxidant N-acetyl cysteine (NAC) protected the cytotoxic effect, suggesting the role of folic acid-induced oxidative stress in cytotoxicity. In contrast, the long-term exposure to folic acid caused increased growth, DNA damage, and changes in the expression of marker genes for EMT, fibrosis, oxidative stress, and oxidative DNA damage. Some of these changes, particularly the acute effects, were abrogated by cotreatment with antioxidant NAC. In summary, the novel findings of this study suggest that higher concentrations of folic acid-induced oxidative stress act as the driver of cytotoxicity as an acute effect and of fibrotic changes as a long-term effect in kidney epithelial cells.

High Folate, Perturbed One-Carbon Metabolism and Gestational Diabetes Mellitus

Folate is a dietary micronutrient essential to one-carbon metabolism. The World Health Organisation recommends folic acid (FA) supplementation pre-conception and in early pregnancy to reduce the risk of fetal neural tube defects (NTDs). Subsequently, many countries (~92) have mandatory FA fortification policies, as well as recommendations for periconceptional FA supplementation. Mandatory fortification initiatives have been largely successful in reducing the incidence of NTDs. However, humans have limited capacity to incorporate FA into the one-carbon metabolic pathway, resulting in the increasingly ubiquitous presence of circulating unmetabolised folic acid (uFA). Excess FA intake has emerged as a risk factor in gestational diabetes mellitus (GDM). Several other one-carbon metabolism components (vitamin B12, homocysteine and choline-derived betaine) are also closely entwined with GDM risk, suggesting a role for one-carbon metabolism in GDM pathogenesis. There is growing evidence from in vitro and animal studies suggesting a role for excess FA in dysregulation of one-carbon metabolism. Specifically, high levels of FA reduce methylenetetrahydrofolate reductase (MTHFR) activity, dysregulate the balance of thymidylate synthase (TS) and methionine synthase (MTR) activity, and elevate homocysteine. High homocysteine is associated with increased oxidative stress and trophoblast apoptosis and reduced human chorionic gonadotrophin (hCG) secretion and pancreatic β-cell function. While the relationship between high FA, perturbed one-carbon metabolism and GDM pathogenesis is not yet fully understood, here we summarise the current state of knowledge. Given rising rates of GDM, now estimated to be 14% globally, and widespread FA food fortification, further research is urgently needed to elucidate the mechanisms which underpin GDM pathogenesis.