Folic acid fortification, folate status and plasma homocysteine

The Role of DNMT Methyltransferases and TET Dioxygenases in the Maintenance of the DNA Methylation Level

This review deals with the functional characteristics and biological roles of enzymes participating in DNA methylation and demethylation as key factors in epigenetic regulation of gene expression. The set of enzymes that carry out such processes in human cells is limited to representatives of two families, namely DNMT (DNA methyltransferases) and TET (DNA dioxygenases). The review presents detailed information known today about each functionally important member of these families and describes the catalytic activity and roles in the mammalian body while also providing examples of dysregulation of the expression and/or activity of these enzymes in conjunction with the development of some human disorders, including cancers, neurodegenerative diseases, and developmental pathologies. By combining the up-to-date information on the dysfunction of various enzymes that control the DNA "methylome" in the human body, we hope not only to draw attention to the importance of the maintenance of a required DNA methylation level (ensuring epigenetic regulation of gene expression and normal functioning of the entire body) but also to help identify new targets for directed control over the activity of the enzymes that implement the balance between processes of DNA methylation and demethylation.

Recent Progress in Folic Acid Detection Based on Fluorescent Carbon Dots as Sensors: A Review

Folic acid (FA) is a water-soluble vitamin found in diverse natural sources and is crucial for preserving human health. The risk of health issues due to FA deficiency underscores the need for a straightforward and sensitive FA detection methodology. Carbon dots (CDs) have gained significant attention owing to their exceptional fluorescence performance, biocompatibility, and easy accessibility. Consequently, numerous research studies have concentrated on developing advanced CD fluorescent probes to enable swift and precise FA detection. Despite these efforts, there is still a requirement for a thorough overview of the efficient synthesis of CDs and their practical applications in FA detection to further promote the widespread use of CDs. This review paper focuses on the practical applications of CD sensors for FA detection. It begins with an in-depth introduction to FA and CDs. Following that, based on various synthetic approaches, the prepared CDs are classified into diverse detection methods, such as single sensing, visual detection, and electrochemical methods. Furthermore, persistent challenges and potential avenues are highlighted for future research to provide valuable insights into crafting effective CDs and detecting FA.

Excess S-adenosylmethionine inhibits methylation via catabolism to adenine

The global dietary supplement market is valued at over USD 100 billion. One popular dietary supplement, S-adenosylmethionine, is marketed to improve joints, liver health and emotional well-being in the US since 1999, and has been a prescription drug in Europe to treat depression and arthritis since 1975, but recent studies questioned its efficacy. In our body, S-adenosylmethionine is critical for the methylation of nucleic acids, proteins and many other targets. The marketing of SAM implies that more S-adenosylmethionine is better since it would stimulate methylations and improve health. Previously, we have shown that methylation reactions regulate biological rhythms in many organisms. Here, using biological rhythms to assess the effects of exogenous S-adenosylmethionine, we reveal that excess S-adenosylmethionine disrupts rhythms and, rather than promoting methylation, is catabolized to adenine and methylthioadenosine, toxic methylation inhibitors. These findings further our understanding of methyl metabolism and question the safety of S-adenosylmethionine as a supplement.

S-adenosylmethionine (SAM) is a widely available dietary supplement. Exogenous SAM is catabolized to adenine, an inhibitor of adenosylhomocysteinase, leading to widespread methylation inhibition and disruption of circadian rhythms in vitro and in mice.

Early Life Nutrition and Mental Health: The Role of DNA Methylation

Does the quality of our diet during early life impact our long-term mental health? Accumulating evidence suggests that nutrition interacts with our genes and that there is a strong association between the quality of diet and mental health throughout life. Environmental influences such as maternal diet during pregnancy or offspring diet have been shown to cause epigenetic changes during critical periods of development, such as chemical modifications of DNA or histones by methylation for the regulation of gene expression. One-carbon metabolism, which consists of the folate and methionine cycles, is influenced by the diet and generates S-Adenosylmethinoine (SAM), the main methyl donor for methylation reactions such as DNA and histone methylation. This review provides current knowledge on how the levels of one-carbon metabolism associated micronutrients such as choline, betaine, folate, methionine and B vitamins that play a role in brain function can impact our well-being and mental health across the lifespan. Micronutrients that act as methyl donors for SAM formation could affect global or gene methylation, altering gene expression and phenotype. Strategies should then be adopted to better understand how these nutrients work and their impact at different stages of development to provide individualized dietary recommendations for better mental health outcomes.

Folate determination in human health: UPLC-MS/MS is the emerging methodology of choice

This Perspective provides a brief description of the essential role that folates play in human health, together with an overview of the various analytical methods that have been used for quantitation of folates in human populations over the past few decades. Essentially, folate methodology has evolved from microbiological assay-based, to binding-based technology and, more recently, to separation-based methodology. Separation-based methods initially used traditional LC in conjunction with various detection techniques, with the most recent methods utilizing UPLC-MS/MS. Current UPLC methods offer exceptional speed, sensitivity and quantitation ability for the monoglutamate folate isoforms. It appears that the only limitation to properly quantifying all folates as polyglutamates, some 40-50 species, is the current lack of corresponding stable-isotope standards. Clearly, UPLC-MS/MS is emerging as the 'method of choice' for the determination of folates, whether in support of basic research, clinical investigations or population studies.

Gene-environment interactions and the risk of childhood acute lymphoblastic leukemia: exploring the role of maternal folate genes and folic Acid fortification

Few studies have evaluated the interaction of folic acid fortification and folate metabolic genes on the risk of childhood acute lymphoblastic leukemia (ALL). Because folate status is influenced by both intake and genetic variation, the objective of this study was to explore maternal folate metabolic gene-folic acid fortification interactions and the risk of childhood ALL. The study population consisted of 120 ALL case-parent triads recruited from Texas Children's Cancer Center between 2003 and 2010. For this analysis, we focused on 13 maternal single nucleotide polymorphisms (SNPs) in 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR). Prefortification was defined as delivery before January 1997 and postfortification as delivery in or after January 1997. We used a two-step approach to evaluate gene-environment interactions. First, a case-only approach was used, as this design provides greater power in the assessment of gene-environment interactions compared to other approaches. Second, we confirmed all statistically significant interactions using a log-linear approach among case-parent triads. Only one of 13 interactions evaluated was confirmed in step 2. Specifically, mothers with the minor allele of MTR rs1804742 and who delivered during the prefortification period were at a greater risk of having a child with ALL (OR = 1.54, 95% CI: 0.82-2.88), compared to those mothers who delivered during the postfortification period (OR = 0.81, 95% CI: 0.22-2.99, P for interaction = .03). In one of the few studies to evaluate maternal folate metabolic genotype-folic acid interactions, we found limited evidence that the maternal MTR rs1804742 appeared to interact with higher folic acid levels to influence childhood ALL risk.

Neural tube defects, folic acid and methylation

Neural tube defects (NTDs) are common complex congenital malformations resulting from failure of the neural tube closure during embryogenesis. It is established that folic acid supplementation decreases the prevalence of NTDs, which has led to national public health policies regarding folic acid. To date, animal studies have not provided sufficient information to establish the metabolic and/or genomic mechanism(s) underlying human folic acid responsiveness in NTDs. However, several lines of evidence suggest that not only folates but also choline, B12 and methylation metabolisms are involved in NTDs. Decreased B12 vitamin and increased total choline or homocysteine in maternal blood have been shown to be associated with increased NTDs risk. Several polymorphisms of genes involved in these pathways have also been implicated in risk of development of NTDs. This raises the question whether supplementation with B12 vitamin, betaine or other methylation donors in addition to folic acid periconceptional supplementation will further reduce NTD risk. The objective of this article is to review the role of methylation metabolism in the onset of neural tube defects.

Lentils (Lens culinaris L.), a rich source of folates

The potential for genetic biofortification of U.S.-grown lentils ( Lens culinaris L.) with bioavailable folate has not been widely studied. The objectives of this study were (1) to determine the folate concentration of 10 commercial lentil cultivars grown in Minot and McLean counties, North Dakota, USA, in 2010 and 2011, (2) to determine the genotype (G) × environmental (E) interactions for folate concentration in lentil cultivars, and (3) to compare the folate concentration of other pulses [field peas ( Pisum sativum L.) and chickpea ( Cicer arietinum L.)] grown in the United States. Folate concentration in lentil cultivars ranged from 216 to 290 μg/100 g with a mean of 255 μg/100 g. In addition, lentil showed higher folate concentration compared to chickpea (42-125 μg/100 g), yellow field pea (41-55 μg/100 g), and green field pea (50-202 μg/100 g). A 100 g serving of lentils could provide a significant amount of the recommended daily allowance of dietary folates (54-73%) for adults. A significant year × location interaction on lentil folate concentration was observed; this indicates that possible location sourcing may be required for future lentil folate research.

Black-white differences in maternal age, maternal birth cohort, and period effects on infant mortality in the US (1983-2002)

We investigate three interrelated sources of change in infant mortality rates over a 20year period using the National Center for Health Statistics (NCHS) linked birth and infant death cohort files. The effects of maternal age, maternal birth cohort, and time period of childbirth on infant mortality are estimated using a modified age/period/cohort (APC) model that identifies age, period, cohort effects. We document black-white differences in the patterning of these effects and find that maternal age effects follow the predictable U-shaped pattern, net of period and cohort, but with a less steep gradient in the black population. The largest relative maternal age-specific disparity in IMR occurs among older African American mothers. Cohort effects, while considerably smaller than age and period effects, present an interesting pattern of a modest decline in IMR among later cohorts of African American mothers coupled with an increasing IMR among the same cohorts of non-Hispanic whites. However, period effects dominate the time trends, implying that period-related technologies overwhelmingly shape US infant survival in today's population. These general findings are mirrored in APC analyses carried out for several leading underlying causes of infant mortality.

Randomized multicenter investigation of folate plus vitamin B12 supplementation in schizophrenia

IMPORTANCE

More effective treatments are needed for negative symptoms of schizophrenia, which are typically chronic, disabling, and costly. Negative symptoms have previously been associated with reduced blood folate levels, especially among patients with low-functioning variants in genes that regulate folate metabolism, suggesting the potential utility of folate supplementation.

OBJECTIVES

To determine whether folic acid plus vitamin B12 supplementation reduces negative symptoms of schizophrenia and whether functional variants in folate-related genes influence treatment response.

DESIGN

Parallel-group, randomized, double-blind, placebo-controlled clinical trial of 16 weeks of treatment with 2 mg of folic acid and 400 μg of vitamin B12.

SETTING

Three community mental health centers affiliated with academic medical centers in the United States.

PARTICIPANTS

Outpatients with chronic schizophrenia who were psychiatrically stable but displayed persistent symptoms despite antipsychotic treatment. Eligible patients were 18 to 68 years old, were treated with an antipsychotic agent for 6 months or more at a stable dose for 6 weeks or more, and scored 60 or more on the Positive and Negative Syndrome Scale.

INTERVENTION

One hundred forty subjects were randomized to receive daily oral folic acid plus vitamin B12 or placebo.

MAIN OUTCOME MEASURES

Change in negative symptoms (Scale for the Assessment of Negative Symptoms [SANS]), as well as positive and total symptoms (Positive and Negative Syndrome Scale).

RESULTS

Folate plus vitamin B12 improved negative symptoms significantly compared with placebo (group difference, -0.33 change in SANS score per week; 95% CI, -0.62 to -0.05) when genotype was taken into account but not when genotype was excluded. An interaction of the 484C>T variant of FOLH1 (rs202676) with treatment was observed (P = .02), where only patients homozygous for the 484T allele demonstrated significantly greater benefit with active treatment (-0.59 change in SANS score per week; 95% CI, -0.99 to -0.18). In parallel, we observed an inverse relationship between red blood cell folate concentration at baseline and 484C allele load (P = .03), which persisted until 8 weeks of treatment. Change in positive and total symptoms did not differ between treatment groups.

CONCLUSIONS

Folate plus vitamin B12 supplementation can improve negative symptoms of schizophrenia, but treatment response is influenced by genetic variation in folate absorption. These findings support a personalized medicine approach for the treatment of negative symptoms.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00611806.

Response of serum and red blood cell folate concentrations to folic acid supplementation depends on methylenetetrahydrofolate reductase C677T genotype: results from a crossover trial

SCOPE

By increasing blood folate concentrations, folic acid supplementation reduces risk for neural tube defect-affected pregnancies, and lowers homocysteine concentrations. We assessed response of red blood cell (RBC) and serum folate to folic acid supplementation, and examined association of response with the genetic polymorphism C677T of the methylenetetrahydrofolate NAD(P)H (MTHFR) gene.

METHODS AND RESULTS

Randomized, controlled, crossover trial with two folic acid supplement treatment periods and a 30-week washout period. The primary outcome is blood folate (serum and RBC) concentrations. Volunteers (n = 142) aged 18-69 were randomized to two of three doses (0, 200, and 400 μg) of folic acid for 12 weeks. Serum folate response depended on treatment period with significant responses to 200 μg seen only in the second treatment periods (4.4 ng/mL or 3.4 ng/mL). Additionally, serum folate increased as folic acid dose increased to 400 μg (p < 0.01) and response was greater after the washout period (8.7 ng/mL), than after a 6-week run-in (2.3 ng/mL). The differential change attributable to a daily supplement of 400 μg compared to 200 μg was 96.8 ng/mL; while the change attributable to 400 μg compared to 0 μg was 121.4. Increases in RBC folate concentrations with 400 μg occurred within MTHFR gene mutation (C677T); and in the African American group.

CONCLUSION

Serum folate concentration is responsive to modest increases in folic acid intake. RBC folate increases only with higher additional doses of folic acid supplementation, and this is true for each MTHFR C677T genotype.

The epigenetic effects of a high prenatal folate intake in male mouse fetuses exposed in utero to arsenic

Inorganic arsenic (iAs) is a complete transplacental carcinogen in mice. Previous studies have demonstrated that in utero exposure to iAs promotes cancer in adult mouse offspring, possibly acting through epigenetic mechanisms. Humans and rodents enzymatically convert iAs to its methylated metabolites. This reaction requires S-adenosylmethionine (SAM) as methyl group donor. SAM is also required for DNA methylation. Supplementation with folate, a major dietary source of methyl groups for SAM synthesis, has been shown to modify iAs metabolism and the adverse effects of iAs exposure. However, effects of gestational folate supplementation on iAs metabolism and fetal DNA methylation have never been thoroughly examined. In the present study, pregnant CD1 mice were fed control (i.e. normal folate, or 2.2 mg/kg) or high folate diet (11 mg/kg) from gestational day (GD) 5 to 18 and drank water with 0 or 85 ppm of As (as arsenite) from GD8 to 18. The exposure to iAs significantly decreased body weight of GD18 fetuses and increased both SAM and S-adenosylhomocysteine (SAH) concentrations in fetal livers. High folate intake lowered the burden of total arsenic in maternal livers but did not prevent the effects of iAs exposure on fetal weight or hepatic SAM and SAH concentrations. In fact, combined folate-iAs exposure caused further significant body weight reduction. Notably, iAs exposure alone had little effect on DNA methylation in fetal livers. In contrast, the combined folate-iAs exposure changed the CpG island methylation in 2,931 genes, including genes known to be imprinted. Most of these genes were associated with neurodevelopment, cancer, cell cycle, and signaling networks. The canonical Wnt-signaling pathway, which regulates fetal development, was among the most affected biological pathways. Taken together, our results suggest that a combined in utero exposure to iAs and a high folate intake may adversely influence DNA methylation profiles and weight of fetuses, compromising fetal development and possibly increasing the risk for early-onset of disease in offspring.

Comprehensive quantitative measurement of folate polyglutamates in human erythrocytes by ion pairing ultra-performance liquid chromatography/tandem mass spectrometry

RATIONALE

The erythrocyte folate pool is reflective of an individual's long-term folate status; however, comprehensive quantitative determination of the various folate isoforms including polyglutamation (Glu(n)) status has posed an analytical problem. Factors complicating such analysis are the absence of authentic (isotope-labeled) standards and the large number of potential analytes. The present work presents high-throughput analytical methodology for the indirect comprehensive quantitation of the erythrocyte folate pool with commercially available standards.

METHODS

The erythrocyte folate pool was determined comprehensively by utilizing a cascade of three complementary ultra-performance liquid chromatography (UPLC) tandem mass spectrometry (MS/MS) assays. In a first assay utilizing ion-pairing UPLC/MS/MS the relative (%) polyglutamation distribution (Glu(3-10)) of 5-methyltetrahydrofolate, tetrahydrofolate and 5-formyltetrahydrofolate is determined in a thermal extract obtained from packed erythrocytes, not requiring analytical standards. Quantitation of the erythrocyte folate pool was accomplished by performing two additional stable isotope dilution UPLC/MS/MS assays to determine whole blood and plasma folate content, utilizing commercially available [(13)C(5)]-labeled analogs of the Glu(1) analytes. Based on the values provided by each individual assay the comprehensive erythrocyte folate content could be calculated.

RESULTS

The various assays have been validated for intra- and inter-run precision, accuracy, linearity and are robust. The method was sensitive enough to measure the comprehensive erythrocyte folate distribution in a Down's syndrome patient with extremely low folate, bearing the C677T mutation in the gene encoding for methylenetetrahydrofolate reductase.

CONCLUSIONS

The erythrocyte folate pool can be comprehensively quantitated by running three complementary UPLC/MS/MS assays. The present assays are robust and allow for high-throughput analysis. The method can be utilized to support larger investigations that investigate the relationship between folate isoform and polyglutamation distribution and disease pathogenesis.

GCPII imaging and cancer

Glutamate carboxypeptidase II (GCPII) in the central nervous system is referred to as the prostate-specific membrane antigen (PSMA) in the periphery. PSMA serves as a target for imaging and treatment of prostate cancer and because of its expression in solid tumor neovasculature has the potential to be used in this regard for other malignancies as well. An overview of GCPII/PSMA in cancer, as well as a discussion of imaging and therapy of prostate cancer using a wide variety of PSMA-targeting agents is provided.

Vitamin food fortification today

Historically, food fortification has served as a tool to address population-wide nutrient deficiencies such as rickets by vitamin D fortified milk. This article discusses the different policy strategies to be used today. Mandatory or voluntary fortification and fortified foods, which the consumer needs, also have to comply with nutritional, regulatory, food safety and technical issues. The ‘worldwide map of vitamin fortification’ is analysed, including differences between develop and developing countries. The vitamins, folate and vitamin D, are taken as practical examples in the review of the beneficial effect of different strategies on public health. The importance of the risk–benefit aspect, as well as how to identify the risk groups, and the food vehicles for fortification is discussed.

Effects of folic acid supplementation on serum folate and plasma homocysteine concentrations in older adults: a dose-response trial

The authors' objective in this study was to estimate the changes in serum folate and homocysteine concentration that resulted from 6 weeks of supplementation with folic acid. A randomized, double-blind, placebo-controlled, dose-response trial with a parallel-group design was conducted. A total of 133 participants aged 60-90 years (70% female, 19% nonwhite) were assigned to receive 0, 100, 400, 1,000, or 2,000 μg/day of folic acid for 6 weeks. Data were collected in the United States between June and September 1996. At baseline, median serum folate and plasma homocysteine concentrations were 5.7 ng/mL (interquartile range (25th-75th percentiles), 4.1-7.8) and 8.3 μmol/L (interquartile range, 7.1-10.0), respectively. As the folic acid dose increased, serum folate levels increased (P-trend < 0.001). There was no dose-response relation with homocysteine level among all participants. In analyses restricted to persons with the lowest serum folate concentration (<4.5 ng/mL) at baseline, there was a trend (P = 0.06) toward decreased homocysteine levels with increasing folic acid dose. In healthy, older adults with adequate folate status, folic acid supplementation is not beneficial for homocysteine reduction. However, for older adults with low serum folate levels, supplementation will improve folate status and may be beneficial for lowering homocysteine concentrations.

Lack of association between the MTHFR (C677T) polymorphism and atopic disease

BACKGROUND

Impaired folate metabolism has been suggested as a potential risk factor for the development of asthma and atopic disease. However, there have been conflicting reports on the potential association between atopic disease and a common polymorphism of the methylene-tetrahydrofolate reductase (MTHFR)-gene, a well-known marker of impaired folate metabolism.

OBJECTIVES

The aim of this study was to investigate the association between the MTHFR (C677T) polymorphism and different outcome variables of asthma and atopic disease.

METHODS

This study was a population-based study of 1189 participants aged 15-77 years living in Copenhagen, the Capital of Denmark. Examinations included measurements of specific IgE and skin prick tests against inhalant allergens, metacholine bronchial hyper-reactivity, and serum eosinophilic cationic protein, and a self-administered questionnaire about diagnoses and symptoms of allergy and asthma. In addition, participants were genotyped for the MTHFR (C677T) polymorphism.

RESULTS

None of the examined outcomes were significantly associated with the MTHFR (C677T) polymorphism.

CONCLUSIONS

The results of this study using detailed objective markers of atopic disease do not support the hypothesis that impaired folate metabolism as reflected by the MTHFR genotype is involved in the development of atopic disease.

Chapter 30: historical aspects of the major neurological vitamin deficiency disorders: the water-soluble B vitamins

This historical review addresses major neurological disorders associated with deficiencies of water-soluble B vitamins: beriberi, Wernicke-Korsakoff syndrome, pellagra, neural tube defects, and subacute combined degeneration of the spinal cord. Beriberi: Beriberi was known for millennia in Asia, but was not described by a European until the 17th century when Brontius in the Dutch East Indies reported the progressive sensorimotor polyneuropathy. The prevalence of beriberi increased greatly in Asia with a change in the milling process for rice in the late 19th century. In the 1880s, Takaki demonstrated the benefits of dietary modification in sailors, and later instituted dietary reforms in the Japanese Navy, which largely eradicated beriberi from the Japanese Navy by 1887. In 1889 Eijkman in Java serendipitously identified dietary factors as a major contributor to "chicken polyneuritis," which he took to be an animal model for beriberi; the polyneuritis could be cured or prevented by feeding the chickens either unpolished rice or rice polishings. By 1901, Grijns, while continuing studies of beriberi in Java, suggested a dietary deficiency explanation for beriberi after systematically eliminating deficiencies of known dietary components and excluding a toxic effect. Wernicke-Korsakoff syndrome: In the late 1870s, Wernicke identified a clinicopathological condition with ophthalmoparesis, nystagmus, ataxia, and encephalopathy, associated with punctate hemorrhages symmetrically arranged in the grey matter around the third and fourth ventricles and the aqueduct of Sylvius. In the late 1880s, Korsakoff described a spectrum of cognitive disorders, including a confabulatory amnestic state following an agitated delirium, occurring in conjunction with peripheral polyneuropathy. Beginning around 1900, investigators recognized the close relationship between Korsakoff's psychosis, delirium tremens, and Wernicke's encephalopathy, but not until several decades later were Wernicke's encephalopathy, Korsakoff's psychosis, and beriberi all linked to the deficiency of a specific dietary factor, i.e. thiamin. Thiamin: Thiamin was crystallized from rice polishings by Jansen and Donath in 1926, and synthesized by Williams and Cline in 1936. In the late 1930s and early 1940s, characteristic pathological changes of Wernicke-Korsakoff syndrome were produced in animal models, the biochemical roles of thiamin in intermediary carbohydrate metabolism were elaborated by Peters and others, and the therapeutic benefits of thiamin for Wernicke-Korsakoff syndrome and beriberi were demonstrated. By the 1950s synthetic forms of the vitamin were produced cheaply, allowing both therapeutic administration and prevention with food enrichment. Pellagra and niacin: Pellagra was unknown prior to the introduction of maize into Europe from the New World. In the 18th century, Casàl and Frapolli described the clinical features of pellagra in Europe, and linked it with poverty and subsistence on nutritionally marginal corn-based diets. In the United States, pellagra became epidemic among poor Southerners in the early 20th century, in part because of economically-driven reliance on monotonous, nutritionally inadequate diets, combined with new manufacturing methods that removed vitamins from processed grain. From 1914-1929, Goldberger completed well-designed epidemiologic investigations, tested theories with human experiments, and utilized an animal model ("black tongue" in dogs) - all strongly supporting a dietary deficiency explanation for pellagra over prevailing toxic and infectious theories. Initial prevention and treatment approaches proved inadequate because of complex social issues linked to poverty, even after Goldberger and colleagues established that dried brewer's yeast could cure or prevent pellagra less expensively than dietary modification. During the depression, the collapse of cotton as an economically viable crop facilitated crop diversification, which contributed to an abrupt decline in pellagra mortality in the early 1930s. In 1937 Elvehjem isolated the P-P (pellagra preventive) factor, identified it as nicotinic acid (niacin), and demonstrated that nicotinic acid and nicotinic acid amide cure black tongue in dogs. Although clinical trials soon confirmed dramatic therapeutic effects in individual people, therapeutic administration of niacin had relatively little impact on population-level morbidity and mortality. Vitamin fortification of foodstuffs during World War II ultimately eradicated endemic pellagra in the United States. In the 1940s and 1950s, with expanded biochemical knowledge, pellagra was reformulated as a deficiency disease due to inadequate niacin and its amino acid precursor tryptophan. Neural tube defects and folate: Folate deficiency was initially recognized clinically as a macrocytic anemia in the 1920s, and only clearly separated from pernicious anemia by the mid-20th century. When folic acid was isolated and synthesized in the 1940s, it was shown to correct the macrocytic anemia associated with pernicious anemia, while the neurological manifestations progressed. In the 1950s and 1960s, the biochemical role of folates in transferring single carbon units was elucidated. Beginning in the 1960s, folate deficiency was increasingly recognized as the major cause of preventable neural tube defects. In the early 1990s well-designed randomized trials established that folate supplementation could prevent neural tube defects. Trial data, collectively indicating that periconceptual folate administration reduces both the occurrence and recurrence risks of neural tube defects by at least 70%, helped establish governmental recommendations concerning folic acid intake and health policy concerning vitamin fortification of foodstuffs. When dietary modification and supplementation strategies proved inadequate, folic acid food fortification was legally mandated in the US in the late 1990s, which significantly improved population folate status and produced an abrupt decline (20%-27%) in the prevalence of neural tube defects at birth. Recent studies have established genetic predispositions for neural tube defects, including both infant and maternal gene polymorphisms for enzymes involved in folate-dependent homocysteine metabolism, which help explain how the genotype of the mother, the genotype of the unborn child, and environmental factors (e.g. folate intake) can all impact on the risk of neural tube defects. Subacute combined degeneration and B(12) deficiency: Pernicious anemia was recognized clinically in the mid-19th century by Addison, but the most important neurological manifestation - subacute combined degeneration of the spinal cord - was not recognized clinically and linked with pernicious anemia until the end of the 19th century, particularly by Lichtheim, Putnam, and Dana. At the beginning of the 20th century, pernicious anemia and the associated subacute combined degeneration of the spinal cord were considered, by many investigators, to result from infectious or toxic causes. During the first quarter of the 20th century, various therapies were employed, but, with the possible exception of transfusion, were largely ineffective. In the 1920s, Minot and Murphy showed that large quantities of ingested liver could be used to effectively treat pernicious anemia, and specifically could improve or prevent progression of neurological manifestations, and could extend life expectancy beyond 2 years. Beginning in the late 1920s, Castle demonstrated that a substance elaborated by the gastric mucosa ("intrinsic factor") was essential for the absorption of a dietary factor ("extrinsic factor," later shown to be vitamin B(12)) needed to prevent pernicious anemia. Over two decades, from the late 1920s until the late 1940s, increasingly potent liver extracts were manufactured that could be given either intramuscularly or intravenously. In 1947, vitamin B(12) was isolated by Folkers and colleagues, and nearly simultaneously by Smith. Shortly thereafter the therapeutic efficacy of vitamin B(12) on subacute combined degeneration was demonstrated by West and Reisner and others. By 1955, Hodgkin determined the molecular structure of cyanocobalamin using computer-assisted x-ray crystallography, allowing complete chemical synthesis of vitamin B(12) in 1960 by an international consortium. Beginning in the late 1950s, the absorption and biochemistry of vitamin B(12) were elaborated, and several lines of evidence converged to support an autoimmune basis for pernicious anemia.

Milk enriched with "healthy fatty acids" improves cardiovascular risk markers and nutritional status in human volunteers

OBJECTIVE

The main goal of the present study was to evaluate the effect of a commercially available milk containing small amounts of eicosapentaenoic acid and docosahexaenoic acid, oleic acid, and vitamins A, B6, D, E, and folic acid compared with semi-skimmed and skimmed milk in volunteers with moderate cardiovascular risk.

METHODS

Two hundred ninety-seven subjects 25 to 65 y of age with moderate cardiovascular risk were randomly allocated into three groups. In addition to their diets, one group consumed 500 mL/d of the enriched milk, another group consumed 500 mL/d of skimmed milk, and a control group consumed 500 mL/d of semi-skimmed milk. All groups consumed the dairy drinks for 1 y and blood samples were taken at 0 and 12 mo.

RESULTS

Consumption of enriched milk for 1 y produced significant (P < 0.05) increases in serum folate (58%) and high-density lipoprotein cholesterol (4%). Plasma triacylglycerols (10%), total cholesterol (4%), and low-density lipoprotein cholesterol (6%) were reduced significantly only in the supplemented group. Serum glucose, homocysteine, and C-reactive protein remained unchanged. In the skimmed milk and semi-skimmed milk groups, the only significant decreases were in serum folate (17% and 11%, respectively).

CONCLUSION

Daily intake of a milk enriched with fish oil, oleic acid, and vitamins improved the nutritional status and cardiovascular risk markers of volunteers, whereas skimmed milk and semi-skimmed milk did not.

The association of homocysteine and related factors to brachial artery diameter and flow-mediated dilation

Brachial artery flow-mediated dilation (BAFMD) has been proposed as a measurement of the degree and severity of cardiovascular disease. The purpose of this study was to (1) evaluate the associations between BAFMD and homocysteine, folate, vitamin B(12), vitamin B(6); (2) examine the influence of 5,10-methylenetetrahydrofolate reductase (MTHFR) genotypes on homocysteine levels and BAFMD; and (3) evaluate the effect of homocysteine on the baseline diameter of the vessel vs BAFMD. A total of 174 healthy research subjects were examined for BAFMD, homocysteine, folate, vitamin B(12), vitamin B(6), and MTHFR genotype, nucleotide 677 C-->T. The data indicated a significant inverse correlation between homocysteine and BAFMD (r = -0.1763, P = .02). There was a significant difference in BAFMD between MTHFR genotype groups (P = .01) (T/T vs C/C, P = .042; C/C vs C/T, P = .13; T/T vs C/T, P = .003). Homocysteine was significantly associated with the baseline brachial artery diameter (r = 0.1878, P = .013). The data confirmed a significant inverse correlation between baseline diameter and BAFMD (r = -0.3321, P = .0001). Regression analysis indicated that the MTHFR genotype, homocysteine, and age were significant predictors of BAFMD (P = .0001, r(2) = 0.118). When the baseline brachial diameter was incorporated into the model, the effect of homocysteine on BAFMD disappeared. The present data indicate an association between homocysteine and BAFMD and reduced BAFMD in individuals with the MTHFR nucleotide 677 T/T genotype, despite similar blood values for folate and homocysteine. Finally, the data suggest that the effect of homocysteine on vascular reactivity is in part a consequence of its influence on baseline brachial artery diameter.

One-third of pregnant and lactating women may not be meeting their folate requirements from diet alone based on mandated levels of folic acid fortification

Many women are advised to consume a folic acid-containing prenatal supplement for the duration of pregnancy and lactation. Whether this remains necessary after folic acid fortification of the food supply in North America has yet to be determined. Our objective was to assess the dietary folate intake of a sample of pregnant and lactating women at mandated and predicted folic acid-fortification levels and determine the prevalence of inadequate and excessive intakes. Weighed food records (for 3 d) were collected from predominantly university-educated women (32 +/- 4 y of age) at 36 wk of pregnancy (n = 61) and at 4 and 16 wk of lactation (n = 60). Dietary folate intakes during pregnancy and lactation, assuming fortification at mandated levels (140-150 micro g/100 g), were 562 +/- 106 and 498 +/- 99 micro g/d dietary folate equivalents (DFE), respectively. The prevalence of inadequacy for folate, or the proportion of individuals with usual folate intakes less than their nutrient requirement, was 36% for women during pregnancy (estimated average requirement of 520 micro g/d DFE), and 32% during lactation (estimated average requirement of 450 micro g/d DFE). Assuming fortification at twice the mandated level, mean dietary intakes during pregnancy and lactation were 786 +/- 132 and 716 +/- 150 micro g/d DFE, respectively, producing only a 3% prevalence of folate inadequacy. Grains contributed approximately 41% of total folate intake followed by fruits and vegetables (approximately 21%). To conclude, at mandated levels of fortification many pregnant and lactating women are unlikely to meet their folate requirements from dietary sources alone; however, the actual level of inadequacy cannot be determined until the level of folic acid in the food supply is known with greater precision.

Population-level changes in folate intake by age, gender, and race/ethnicity after folic acid fortification

OBJECTIVES

We sought to quantify the impact of the 1998 US Food and Drug Administration (FDA) folic acid fortification policy by estimating folate intake at the population level.

METHODS

We analyzed total folate intake levels (from food and supplements) according to gender, age, and race/ethnicity, using data from 2 National Health and Nutrition Examination Surveys. We measured pre- and postfortification folate intake distributions, adjusted for measurement error, and examined proportions of the population who reached certain thresholds of daily total folate intake.

RESULTS

Mean daily food and total folate intake increased by approximately 100 microg/day after fortification. The proportion of women aged 15-44 years who consume more than 400 microg/day of folate has increased since fortification, but has not yet reached the FDA's 50% target and varies by race/ethnicity from 23% to 33%. Among persons aged 65 years and older who may be at risk for masking a vita-microg/day (the min B12 deficiency, the percentage who consume more than 1000 "tolerable upper intake level") has at least doubled among Whites and Black men, but has remained less than 5% for all groups.

CONCLUSIONS

Since fortification, folic acid intake among the US population has increased, and there are substantial variations by age, gender, and race/ethnicity.

Nutritional determinants of plasma total homocysteine distribution in the Canary Islands

OBJECTIVE

We sought to define plasma homocysteine reference values in healthy individuals in the Canary Islands and to determine its relations to folate and vitamin B12 intakes and concentrations.

DESIGN

Cross-sectional study.

SETTING

Population-based representative sample of 557 participants, aged 18-65 years, from the Canary Islands Nutrition Survey (ENCA).

SUBJECTS

All participants completed two 24-h dietary recalls and a general questionnaire collecting socio-demographic and health-related lifestyle information.

INTERVENTIONS

Plasma homocysteine and serum vitamin B12 levels were measured by immunoassay, whereas folate levels through an automated ionic capturing method.

RESULTS

Median plasma homocysteine was 11.9 micromol/l, higher in men (13.1 micromol/l) than in women (10.9 micromol/l) (P<0.001) and positively associated with age in both sexes (P<0.001). The prevalence of hyperhomocysteinaemia (> or = 15 micromol/l), 21.4%, was also greater in men (32.2%) than in women (13.4%). There were significant negative correlations between plasma homocysteine and serum (r=-0.32, P<0.001) and erythrocyte (r=-0.26, P<0.001) folate, as well as serum vitamin B12 (r=-0.28, P<0.001) concentrations. When divided in quartiles of vitamin intakes or concentrations, men with the lowest vitamin B12 and folate serum values had significantly higher plasma homocysteine concentrations than those in the other three quartiles. In women, hyperhomocysteinaemia was higher in the lowest quartiles of folate intake and serum and erythrocyte folate concentrations.

CONCLUSIONS

These data provide further evidence that hyperhomocysteinaemia is a sensitive marker of inadequate folate and vitamin B12 status, allowing for the identification of those with greatest need for nutritional interventions.

Effects of riboflavin and folic acid supplementation on plasma homocysteine levels in healthy subjects

BACKGROUND

Observational studies have shown an inverse relationship between vitamin B2 status and total homocysteine levels, a risk factor for cardiovascular disease. We hypothesize that intervention with riboflavin will lower total homocysteine levels. The total homocysteine lowering by the three genotypes (CC, CT, TT) of methylenetetrahydrofolate reductase polymorphism (677C-->T) was also studied.

METHODS

The decrease in total homocysteine levels after supplementation with riboflavin (10 mg/d) or folic acid (1 mg/d) for 3 weeks was compared in two groups of healthy subjects (17 per group, matched by age and gender) (Phase 1). Then, both groups received supplementation with folic acid and riboflavin for an additional 3 weeks (Phase 2).

RESULTS

During Phase 1, total homocysteine levels were lowered by 2% or 4% after supplementation with riboflavin or folic [corrected] acid, respectively, although neither decrease was statistically significant (P=0.50 and 0.19). Compared to subjects of CC genotype, total homocysteine lowering in subjects of CT genotype was approaching significance (P=0.059) for the folic acid group, but not for the riboflavin group. After Phase 2, total homocysteine levels were not lowered significantly in either the folic acid (1%) or the riboflavin (2%) group. However, in the folic acid-riboflavin combined group, total homocysteine lowering in subjects of TT type was larger when compared to subjects of CC and CT types (P=0.007).

CONCLUSIONS

Riboflavin supplementation did not lower total homocysteine levels in healthy subjects with CC type of C677T polymorphism. However, supplementation with folic acid or with both folic acid and riboflavin may be important for CT and TT subjects in optimizing their homocysteine metabolism. These findings are relevant in characterizing the factors controlling the high total homocysteine levels for subjects of CT and TT genotypes.

Serum homocysteine concentration of US adults associated with fortified cereal consumption

BACKGROUND

Elevated serum total homocysteine (tHcy) concentration is implicated in the etiology of cardiovascular disease (CVD). A significant food source of B-vitamins involved in homocysteine metabolism is ready-to-eat cereal (RTEC) in the U.S.

OBJECTIVE

To test the hypothesis that tHcy concentration is inversely associated with RTEC intake and blood B-vitamin levels in the U.S. general population.

DESIGN

A cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES 1999-2000). Data were stratified according to age and gender. Men and women > or = 19 y (n = 4,218) were classified as RTEC consumers (RTEC-C; n = 824) and RTEC non-consumers (RTEC-NC; n = 3,394) based on 24-hr dietary recall.

RESULTS

Forty nine percent of participants showed folate intake with below the estimated average requirements (EARS). Serum folate and red blood cell (RBC) folate concentrations were increased with age in both genders, and significantly higher among RTEC-C than RTEC-NC (p < 0.05). Mean tHcy concentration increased with age, and was significantly lower among both men and women RTEC-C than among RTEC-NC. In multivariate linear regression analyses, RTEC consumption strongly predicted serum folate and tHcy concentrations.

CONCLUSION

tHcy concentrations were significantly lower in RTEC-C among the majority of age/gender groups than in RTEC-NC. RTEC consumption may potentially reduce the risk for CVD, mediated through tHcy.

Vitamin Intervention for Stroke Prevention Trial

Background and Purpose— The Vitamin Intervention for Stroke Prevention trial (VISP) intention-to-treat analysis did not show efficacy of combined vitamin therapy for recurrent vascular events in patients with nondisabling stroke. Reasons for lack of efficacy may have included folate fortification of grain products, inclusion of the recommended daily intake for B 12 in the low-dose arm, treatment with parenteral B 12 in patients with low B 12 levels in both study arms, a dose of B 12 too low for patients with malabsorption, supplementation with nonstudy vitamins, and failure of patients with significant renal impairment to respond to vitamin therapy. We conducted an efficacy analysis limited to patients most likely to benefit from the treatment, based on hypotheses arising from evidence developed since VISP was initiated. The criteria for this subgroup were defined before any data analysis.

Methods— For this analysis, we excluded patients with low and very high B 12 levels at baseline (<250 and >637 pmol/L, representing the 25th and 95th percentiles), to exclude those likely to have B 12 malabsorption or to be taking B 12 supplements outside the study and patients with significant renal impairment (glomerular filtration rate <46.18; the 10th percentile).

Results— This subgroup represents 2155 patients (37% female), with a mean age of 66±10.7 years. For the combined end point of ischemic stroke, coronary disease, or death, there was a 21% reduction in the risk of events in the high-dose group compared with the low-dose group (unadjusted P =0.049; adjusted for age, sex, blood pressure, smoking, and B 12 level P =0.056). In Kaplan–Meier survival analysis comparing 4 groups, patients with a baseline B 12 level at the median or higher randomized to high-dose vitamin had the best overall outcome, and those with B 12 less than the median assigned to low-dose vitamin had the worst ( P =0.02 for combined stroke, death, and coronary events; P =0.03 for stroke and coronary events).

Conclusions— In the era of folate fortification, B 12 plays a key role in vitamin therapy for total homocysteine. Higher doses of B 12 , and other treatments to lower total homocysteine may be needed for some patients.

Maternal plasma homocysteine concentrations are not increased in twin pregnancies

OBJECTIVE(S)

We tested the hypothesis that twin pregnancies would lead to increased maternal plasma homocysteine. We further hypothesized that twin pregnancies complicated by preeclampsia would have increased plasma homocysteine compared to twin pregnancies without preeclampsia and normal singleton pregnancies.

METHODS

Plasma was collected at delivery from 127 nulliparous subjects: 57 women with normal singleton pregnancies, 39 women with singleton and preeclampsia, 17 women with uncomplicated twin pregnancies, and 14 women with twins and preeclampsia. Subjects were group matched for prepregnancy body mass index (BMI) and race. Plasma homocysteine was analyzed by high pressure liquid chromatography (HPLC) with fluorescence detection, and plasma folic acid was measured by radio immunoassay (RIA).

RESULTS

The mean plasma concentration of homocysteine was significantly increased in all women with preeclampsia (7.4+/-2.9 microM) compared to all normal pregnant women (5.9+/-2.1 microM, p=0.002). However, homocysteine was not significantly increased in all women with twins (6.7+/-2.1 microM) compared to all women with singleton pregnancies (6.5+/-2.7 microM, p=0.61). In addition, women with twins and preeclampsia did not have increased homocysteine (6.8+/-2.1 microM) compared to women with twins and normal pregnancy (6.7+/-2.1 microM, p=0.72). As expected, because of extra supplementation, plasma folic acid was significantly increased in women with twins (27.9+/-11.6 ng/mL) compared to women with singleton pregnancies (20.8+/-8.5 ng/mL, p=0.0003). However, folic acid was not different between preeclamptics and controls (23.5+/-10.8 vs. 21.9+/-9.2 ng/mL respectively, p=0.36). Lastly, there was a significant inverse correlation between homocysteine and folic acid among all the subjects (r2=- 0.053, p< 0.01), and this correlation persisted in the women with singleton pregnancies (r2=- 0.078, p< 0.01), but was lost in the twins (r2=- 0.073, p=0.14).

CONCLUSIONS

With contemporary management including increased folic acid supplementation, plasma homocysteine is not increased in twin pregnancies with or without preeclampsia.

Folate intake estimated with an updated database and its association to blood folate and homocysteine in Korean college students

OBJECTIVE

To measure folate content in cooked foods commonly consumed in Korea for evaluating its relation to folate nutriture of college students.

DESIGN

Folate content in 32 raw and cooked foods was measured by microbiological assay after trienzyme extraction. These values and the previously published values of 110 raw foods commonly consumed in Korea were used to update the currently available food tables to estimate dietary folate intake of 106 students based on a 3-day 24-h recall. The association of folate intake with blood folate and homocysteine concentrations was evaluated.

SETTING

Cheongju, Korea.

SUBJECTS

Healthy college students aged 18 to 27 y old (44 males and 62 females).

RESULTS

The average folate loss in 32 foods caused by cooking was 29%. The mean daily dietary folate intakes estimated with an updated database were 406 and 305 mug in males and females, respectively. About 10% of both male and female students showed low serum folate (<6.8 nmol/l). Folate intake was positively correlated with serum and erythrocyte folate concentrations in female students (r=0.27 and 0.29, respectively, P<0.05), and negatively correlated with serum homocysteine in male students (r=-0.41, P<0.05).

CONCLUSIONS

Mean dietary folate intake was higher than those of previous studies since the database was updated using values obtained with trienzyme extraction. Folate intake for the general population should be re-evaluated using reliable food folate values obtained with trienzyme extraction.

Folate content in commercial white and whole wheat sandwich breads

After the U.S. mandate of folic acid fortification of enriched grain products, a report indicated higher than expected fortification. Limited information is available on folic acid in enriched products. We measured the folate content in 92 sandwich breads (46 white breads and 46 whole wheat breads) in Birmingham, Alabama, during 2001-2003. The mean folate content in white bread declined significantly from 2001 to 2002 or 2003, whereas the decline in folate content in whole wheat bread containing enriched flour was not significant. White bread contained significantly more folate than whole wheat bread containing enriched flour in 2001 and 2003. In 2002 and 2003, >40% of breads made of enriched flour contained <115 microg of folate/100 g and >70% contained <160 microg/100 g. These percentages were markedly higher than those in 2001. Our data suggest that folic acid in breads containing enriched flour declined after 2001 and monitoring of fortification may be necessary.

Fortifying food with folic acid improves folate intake in German infants, children, and adolescents

Folate is a critical nutrient and programs to enhance folate intake have been established or are under consideration. We investigated to what extent consumers (C) profit from folic acid-fortified food and dietary supplements compared to nonconsumers (NC) of these products. A total of 6135 weighed records from 861 subjects (47% males, 53% females, age 6 mo to 18 y) from the Dortmund Nutritional and Anthropometric Longitudinally Designed Study between 1990 and 2001 were evaluated. In 61% of the records, at least 1 item fortified with folic acid was reported, and in total 644 different items with a wide range of fortification levels were found. These were primarily commercial infant food (i.e., infant formula, weaning food) (44%), breakfast cereals (20%), and soft drinks (11%). Median dietary folate equivalents (DFEs) in NC increased from 65 and 62 microg/d in boys and girls at 6-12 mo of age, respectively, to 184 and 143 microg/d in adolescents 15-18 y of age. In C, DFEs increased from 109 and 100 microg/d in boys and girls at 6-12 mo of age, respectively, to 370 and 276 microg/d in adolescents 15-18 y of age. Irrespective of gender, NC had 50-70% the DFE intakes of C with a tendency for higher percentages in younger than in older children and adolescents. Folate intakes by male and female consumers of fortified food or supplements exceeded the upper levels in 1.7 and 1.2% of subjects, respectively. Currently, a fortification program for staple foods (e.g., grain products) does not seem necessary in Germany if children and adolescents consume food already fortified with folic acid.

Modeling the level of fortification and post-fortification assessments: U.S. experience

Mandatory fortification of enriched cereal-grain products became effective in the United States on January 1, 1998. This fortification was undertaken to assist women of child-bearing age in increasing their intake of folic acid to reduce their risk of having a pregnancy affected by a neural tube birth defect. The process by which the Food and Drug Administration modeled the level of fortification with folic acid illustrates the complex issues and general principles that emerge when fortification of a nation's food supply is evaluated as a means of addressing a public health concern. The effectiveness of fortification for a target population and safety for the much larger general population impose conflicting challenges that must be considered concurrently when making decisions regarding fortification. Recent data show improved folate status and apparent decreases in risk of neural tube birth defects in the U.S. Much about the long-term effects of the fortification program remains unknown and careful monitoring over time will be necessary to ensure that the program functions as intended.

Cardiovascular effects of milk enriched with ω-3 polyunsaturated fatty acids, oleic acid, folic acid, and vitamins E and B6 in volunteers with mild hyperlipidemia

OBJECTIVE

Results from epidemiologic studies and clinical trials have indicated that consumption of omega-3 fatty acids, oleic acid, and folic acid have beneficial effects on health, including decreased risk of cardiovascular disease. We evaluated the combined effects of these nutrients through the consumption of milk enriched with omega-3 polyunsaturated fatty acids, oleic acid, vitamins E and B6, and folic acid on risk factors for cardiovascular disease in volunteers with mild hyperlipidemia.

METHODS

Thirty subjects ages 45 to 65 y (51.3 +/- 5.3 y) were given 500 mL/d of semi-skimmed milk for 4 wk and then 500 mL/d of the enriched milk for 8 wk. Plasma and low-density lipoproteins were obtained at the beginning of the study and at 4, 8, and 12 wk.

RESULTS

Consumption of enriched milk for 8 wk increased plasma concentrations of docosahexaenoic acid and eicosapentaenoic acid and significantly (P < 0.05) decreased plasma concentrations of triacylglycerol (24%), total cholesterol (9%), and low-density lipoprotein cholesterol (13%). Plasma and low-density lipoprotein oxidation and vitamin E concentration remained unchanged throughout the study. Significant decreases in plasma concentrations of vascular cell adhesion molecule-1 (9%) and homocysteine (17%) were found, accompanied by a 98% increase in plasma concentration of folic acid.

CONCLUSIONS

Dairy supplementation strategies with omega-3 polyunsaturated fatty acids, oleic acid, and vitamins may be useful for decreasing risk factors for cardiovascular disease.

Effect of folic acid fortification of foods on folate intake in female smokers with cervical dysplasia

OBJECTIVE

We investigated the effect of folic acid fortification of enriched cereal grains on folate intake in women of predominantly childbearing age at high risk for cervical cancer.

METHODS

Subjects in this cross-sectional study were 77 women randomized between November 1999 and December 2000 in the Women's Intervention to Stay Healthy (WISH), a clinical trial evaluating the effect of a tobacco control intervention on the progression of cervical dysplasia. All subjects were cigarette smokers, had a previously abnormal Papanicolaou test, and were positive for high-risk human papillomavirus at entry. Dietary intake was assessed with food-frequency questionnaires completed at the baseline visit for WISH. The effect of folic acid fortification on folate intake was assessed by using pre- and postfortification folate databases to estimate folate intake.

RESULTS

Mean folate intake assessed with the postfortification database was 63% higher than intake assessed with the prefortification database: 417 versus 256 microg/d of dietary folate equivalents (P < 0.0001). The proportion of subjects below the estimated average requirement for folate was smaller after fortification than before fortification: 40.3% versus 75.3% (P < 0.0001). Several foods, including white bread, cheese dishes, spaghetti, and rice, became major sources of folate as a result of fortification.

CONCLUSIONS

Folic acid fortification resulted in an increased intake of folate in these subjects. However, even with fortification, folate intake in a large proportion of these women remained below recommended levels. These results should be considered before decisions regarding future levels of folic acid fortification are made.

Folate and homocysteine interrelationships including genetics of the relevant enzymes

PURPOSE OF REVIEW

Inadequate folate status has been linked to risk of a wide range of adverse health conditions throughout life, from birth defects and complications of pregnancy to cardiovascular disease, cancer and cognitive dysfunction in the elderly. In many instances these risks are manifested through elevated plasma homocysteine. This review focuses on current research into the contribution of genetic variability to folate status and disease predisposition.

RECENT FINDINGS

Some dozen potentially important polymorphisms in folate-related genes have been examined for disease associations or for their role in determining the level of plasma homocysteine. In most instances, the effects are either modest, not significant, or undetectable. However, the mechanism by which the 677C-->T variant of methylenetetrahydrofolate reductase determines homocysteine status has become clearer with the elucidation of a critical role for riboflavin in modulating the plasma homocysteine of TT homozygotes. Moreover, several new metaanalyses have confirmed an association of this variant with vascular disease, probably through low folate status and elevated plasma homocysteine.

SUMMARY

There are enormous difficulties in attempting to assess the contribution of minor genetic variability to nutrient status, against major background differences due to ethnicity, age, gender, lifestyle, dietary habits and disease status. Nevertheless, this is an important goal in the future management of chronic multifactorial disease. The present research into the genetic components of folate and homocysteine variability is paving the way towards an eventual capacity to ensure optimal folate status in every individual and, consequently, to reduce their risk of developing such diseases.

Mineral water fortified with folic acid, vitamins B6, B12, D and calcium improves folate status and decreases plasma homocysteine concentration in men and women

OBJECTIVE

We investigated the effects of mineral water fortified with folic acid, vitamins B(6), B(12), D and calcium on folate concentrations in serum and erythrocytes, serum vitamin B(12) and plasma homocysteine concentrations in free-living subjects. In addition, we investigated the bioavailability of calcium added to mineral water by measuring urinary calcium excretion and serum alkaline phosphatase activity.

DESIGN

Randomized, controlled, double-blinded, parallel design.

SETTING

Outpatient dietary intervention with free-living subjects in Eastern Finland.

SUBJECTS

Altogether, 66 subjects were recruited for the study. In all, 60 subjects completed the study.

INTERVENTIONS

The study began with a 2-week run-in period followed by an 8-week intervention period. During the intervention study, subjects consumed mineral water fortified with folic acid (563 microg/day), vitamins B(6) (1 mg/day), B(12) (7.5 microg/day), cholecalciferol (0.6 microg/day) and calcium (563 mg/day) or placebo mineral water.

RESULTS

The fortified mineral water increased serum and erythrocyte folate concentrations by 16.1+/-5.6 nmol/l (P<0.001) and 199+/-76 nmol/l (P<0.001), respectively, and decreased plasma homocysteine concentration by 1.6 micromol/l (P<0.001). Urinary calcium excretion and serum alkaline phosphatase activity for 24 h increased significantly (P<0.001 and P=0.01 respectively) in the intervention group.

CONCLUSIONS

Mineral water fortified with folic acid, vitamins B(6), B(12) and D and calcium enhanced folate status and reduced plasma homocysteine concentration in normohomocysteinemic subjects without folate deficiency. Indirect measures of calcium and bone metabolism indicated that the calcium used in the fortification of the mineral water was bioavailable.

Antagonism of Hypervitaminosis A-Induced Anterior Neural Tube Closure Defects with a Methyl-Donor Deficiency in Murine Whole-Embryo Culture

The interaction of a dietary excess of vitamin A (retinoid) and deficiency of methyl-donor compounds was examined in murine early-organogenesis embryonic development. Female mice were fed one of six diets from the time of vaginal plug detection until gestational d 8.0, when embryos were removed and grown in whole embryo culture for 46 h, using serum from rats fed the same diet for 36 d as the culture medium. The six diets were either methyl-donor deficient (designated -FCM: devoid of folic acid, choline and supplemental L-methionine, but having methionine as a component of the protein portion of the diet) or methyl-donor sufficient (designated +FCM: containing folic acid, choline and L-methionine supplementation), in combination with one of three concentrations of retinyl palmitate (0.016, 0.416 or 4.016 g/kg diet). The high dose of retinyl palmitate induced a failure of anterior neuropore closure and hypoplasia of the visceral arches, both of which were significantly ameliorated by simultaneous administration of the methyl-donor-deficient diet. The primary acidic retinoid detected in the rat serum was 9,13-di-cis-retinoic acid, although we hypothesize that teratogenic retinoids were formed by embryonic biotransformation of the retinyl esters to toxic metabolites. Biochemical measurements of metabolites in relevant pathways were performed. We propose that the amelioration of these malformations may be used to determine biochemical pathways critical for retinoid teratogenesis.

Hyperhomocysteinemia and its role in the development of atherosclerosis

Numerous epidemiological studies have demonstrated that hyperhomocysteinemia (HHcy) is a strong and independent risk factor for cardiovascular disease. HHcy can result from a deficiency in the enzymes or vitamin cofactors required for homocysteine metabolism. Several hypotheses have been proposed to explain the cellular mechanisms by which HHcy promotes cardiovascular disease, including oxidative stress, endoplasmic reticulum (ER) stress and the activation of pro-inflammatory factors. Studies using genetic- and diet-induced animal models of HHcy have now demonstrated a direct causal relationship between HHcy, endothelial dysfunction and accelerated atherosclerosis. These recently established animal models of HHcy provide investigators with important in vivo tools to (i) further understand the cellular mechanisms by which HHcy contributes to endothelial dysfunction and atherosclerosis, and (ii) develop therapeutic agents useful in the treatment of cardiovascular disease.

News and views on folate and elderly persons

Elderly persons are especially exposed to folate deficiency, where normal/subnormal folate levels do not exclude tissue deficiency. Accompanying diseases, medication, and lifestyle factors may contribute to/cause deficiency. Symptoms of deficiency can be hematological, neurological, or neuropsychiatric, but it is likely that there are also cardiovascular manifestations as well as associations with malignancies. The physician should make an individualized investigation to establish the probable cause. Among the available determinants of the folate/cobalamin state, plasma homocysteine (Hcy) is a swift and sensitive marker and has the strongest connection to cognitive function. The association is generally stronger between Hcy levels and symptoms than between vitamin-related levels and symptoms. The duration as well as the severity of symptoms are of importance in terms of the improvement of neurological and neuropsychiatric symptoms when substitution is performed. The issue of general folate fortification of flour is complex, and there are as many pros and cons as there are countries in which it is considered to be launched. It is important to bear in mind that in our modern society, deficiency of folate/cobalamin--overt or latent--mainly is a problem of the elderly and a challenge to the doctor.