A long-term controlled folate feeding study in young women supports the validity of the 1.7 multiplier in the dietary folate equivalency equation

Effects of acute strawberry consumption on serum levels of vitamin C and folic acid, the antioxidant potential of LDL and blood glucose response: a randomised cross-over controlled trial

Strawberry contains many bioactive compounds such as vitamin C and polyphenols as well as folate, a vitamin that is especially important for women of childbearing age. We investigated the effects of the acute consumption of strawberry on the serum levels of vitamin C and folate, and on the antioxidant potential of low-density lipoprotein (LDL). In a randomised, placebo-controlled, double-blind, crossover study, twenty-three healthy female volunteers (age 22⋅5 ± 1⋅4 years) ingested 500 g of a strawberry purée beverage or a sugar content-matched placebo beverage. Blood samples were collected at fasting and at 0⋅5, 1, 2 and 4 h post-ingestion. The serum concentrations of vitamin C and folate were significantly elevated from 0⋅5 to 4 h after the strawberry beverage ingestion (P < 0⋅001); the levels peaked at 2 h, with peak levels of 15⋅0 ± 2⋅5 μg/ml for vitamin C and 14⋅4 ± 7⋅0 ng/ml for folate. Notably, at 1 h after the strawberry beverage ingestion, the LDL oxidation lag time was significantly prolonged (P < 0⋅05), suggesting that the antioxidant potential of LDL was increased. After the ingestion of either beverage, the serum levels of glucose and insulin reached a peak at 0⋅5 h and then quickly returned to baseline levels. These results suggest that strawberries are a useful source of vitamin C and folate and may help enhance the antioxidant potential of LDL in healthy young women.

Associations between Folate and Alcohol Consumption with Colorectal Tumor Ki67 Expression in the Southern Community Cohort Study

Folate is hypothesized to accelerate cell proliferation in colorectal cancer (CRC) by supporting DNA synthesis, while alcohol is also linked to gastrointestinal epithelial proliferation, despite biological antagonism of folate. We report associations between folate and alcohol consumption with the proliferation marker Ki67 in CRC tumors from the Southern Community Cohort Study. Tumor samples were obtained from formalin-fixed paraffin-embedded tissue blocks. The percentage of cells expressing Ki67 was measured immunohistochemically. Exposures were assessed via questionnaire pre-diagnosis. Associations were assessed via linear regression. In 248 cases (40-78 years), neither dietary folate, folic acid supplements, nor total folate intake were associated with Ki67. Folic acid supplement use was associated with Ki67 in distal/rectal tumors (β [95% confidence interval]: 7.5 [1.2-13.8], p = .02) but not proximal tumors (-1.4 [-7.1-4.3], p=.62). A positive trend for total folate was observed for distal/rectal tumors (1.6 [0.0-3.3] per 200 μcg, p-trend=.05). Heavy drinking (women: ≥1 drink/day, men: ≥2 drinks/day) was associated with higher Ki67 (6.4 [1.0-11.9], vs. nondrinkers, p=.02), especially for distal/rectal tumors (10.4 [1.6-19.1], p=.02). Negative interaction between alcohol, total folate was observed for distal/rectal tumors (p-interaction=.06). Modest associations between folate, alcohol consumption and distal/rectal tumor Ki67 expression suggest accelerated proliferation, consistent with folate's role in DNA synthesis.

Quantitation of 5-methyltetraydrofolic acid in plasma for determination of folate status and clinical studies by stable isotope dilution assays

Folates play a key role in the prevention of neural tube defects in newborns. Thus, it is important to reliably determine the bioavailability of folates from various foods. Accurate analytical methods are essential for quantifying blood-folates, especially in human studies. Here, we present the development and validation of a sensitive method using stable isotope dilution liquid chromatography coupled with mass spectrometry for determining various folates in plasma. Moreover, this study reports the applicability of the developed method to a human pilot study using strawberries as a test food. Validation of the assay revealed the precision, sensitivity, and accuracy of the method in determining the predominant 5-methyltetrahydrofolate in plasma. This method was also applicable for the screening of individual folate status using finger prick blood and for monitoring the post-absorptive plasma-concentration curve. Moreover, the human study revealed a high recovery of strawberry folates with a calculated relative bioavailability of 96.2%. Thus, the developed method enables prospective bioavailability studies. This work also confirmed, via human studies, that strawberries are a rich and natural source of folates that are available for human metabolism.

The Vitamins Involved in One-Carbon Metabolisms are Associated with Reduced Risk of Breast Cancer in Overall and Subtypes

Background: Some micronutrients like folate, vitamin B12, B6, and B2 are the source of coenzymes, which participate in one-carbon metabolism. Any disruption in this metabolism can interfere with DNA replication, repair and regulation of gene expression and ultimately promote the likelihood of carcinogenesis. This study aimed at investigating the relationship between the intakes of micronutrients involved in one-carbon metabolism with breast cancer (BrCa) and its subtype's odds. Methods: Nutrients' intake from diet and supplements were collected through interviewing 151 cases and 154 controls by a 168-item semiquantitative food frequency questionnaire. Logistic regression was used to determine the relationship between dietary and/or total intake of studied nutrients and odds of BrCa and its subtypes. Results: After adjusting the effects of confounding variables in the models, the odds of BrCa was significantly lower in the highest intake quartile compared with the lowest quartile for total intake of vitamin B2 (OR = 0.17, 95% CI, 0.07-0.39; P_trend < 0.001), vitamin B6 (OR = 0.11, 95% CI, 0.05-0.27; P_trend < 0.001), vitamin B12 (OR = 0.20, 95% CI, 0.09-0.43; P_trend < 0.001) and folate (OR = 0.09, 95% CI, 0.04-0.21; P_trend < 0.001). Also, those with the highest quartile of vitamin B6, B12, B2 and folate intake compared with the lowest quartile were less likely to develop estrogen receptor (ER)+ and progesterone receptor (PR)+ subtypes, ER- status, PR- and human epidermal growth factor receptor 2 (HER2)+ subtypes and HER2- status. Conclusion: High intakes of vitamins B2, B6 and folate are associated with reduced odds of BrCa in overall and all ER, PR and HER2 subtypes. Also, high intakes of vitamin B12 reduced the odds of all subtypes of BrCa except ER- subtype.

A Cross-Sectional Study of Dietary and Genetic Predictors of Blood Folate Levels in Healthy Young Adults

Since 1998, the U.S. has mandated folic acid (FA) fortification of certain grain products to reduce the risk of neural tube defects. Folate intake and red blood cell (RBC) folate concentrations increased substantially post-intervention, although recent studies raise concerns about the level of ongoing benefit. This study investigated blood folate level determinants in healthy young adults, including intake of naturally occurring food folate, synthetic FA, and the interaction of naturally occurring food folate with a common missense variant in the FOLH1 gene thought to affect absorption. Participants (n = 265) completed the Diet History Questionnaire II, RBC folate testing, and were genotyped for the 484T>C FOLH1 variant. Men reported significantly greater intake of all folate sources except for supplemental FA, but RBC folate levels did not significantly differ by sex. Synthetic FA was a stronger predictor of RBC folate than naturally occurring food folate. In the largest racial group, synthetic FA and the interaction of FOLH1 genotype with naturally occurring food folate significantly predicted RBC folate, with the overall model accounting for 13.8% of the variance in RBC folate levels. Blood folate levels rely on a complex interaction of natural and synthetic folate intake as well as FOLH1 genotype.

Folates: Chemistry, analysis, occurrence, biofortification and bioavailability

Folates (Vitamin B₉) include both naturally occurring folates and synthetic folic acid used in fortified foods and dietary supplements. Folate deficiency causes severe abnormalities in one-carbon metabolism can result chronic diseases and developmental disorders, including neural tube defects. Mammalian cells cannot synthesize folates de novo; therefore, diet and dietary supplements are the only way to attain daily folate requirements. In the last decade, significant advancements have been made to enhance the folate content of rice, tomato, common bean and lettuce by using genetic engineering approaches. Strategies have been developed to improve the stability of folate pool in plants. Folate deglutamylation through food processing and thermal treatment has the potential to enhance the bioavailability of folate. This review highlights the recent developments in biosynthesis, composition, bioavailability, enhanced production by elicitation and metabolic engineering, and methods of analysis of folate in food. Additionally, future perspectives in this context are identified. Detailed knowledge of folate biosynthesis, degradation and salvage are the prime requirements to efficiently engineer the plants for the enhancement of overall folate content. Similarly, consumption of a folate-rich diet with enhanced bioavailability is the best way to maintain optimum folate levels in the body.

Folate content in faba beans (Vicia faba L.)-effects of cultivar, maturity stage, industrial processing, and bioprocessing

Faba beans are an important source of folate and commonly consumed in Egypt. This study examined the effects of Egyptian industrial food processing (e.g., canning and freezing), germination, cultivar, and maturity stages on folate content, with the aim to develop a candidate functional canned faba bean food with increased folate content. The folate content in four cultivars of green faba beans ranged from 110 to 130 μg 100 g⁻¹ fresh weight (535–620 μg 100 g⁻¹ dry matter [DM]), which was four- to sixfold higher than in dried seeds. Industrial canning of dried seeds resulted in significant folate losses of ∼20% (P = 0.004), while industrial freezing had no effect. Germination of faba beans increased the folate content by >40% (P < 0.0001). A novel industrial canning process involving pregermination of dried faba beans resulted in a net folate content of 194 μg 100 g⁻¹ DM, which is 52% more than in conventional canned beans. The consumption of green faba beans should be recommended, providing ∼120 μg dietary folate equivalents per 100 g/portion.

Associations of dietary folate, Vitamins B6 and B12 and methionine intake with risk of breast cancer among African American and European American women

African American (AA) women are more likely than European American (EA) women to be diagnosed with breast cancer at younger ages and to develop poor prognosis tumors. However, these racial differences are largely unexplained. Folate and other methyl-group nutrients may be related to breast carcinogenesis, but few studies have examined these associations in AA populations. We examined the associations of dietary intake of these nutrients with breast cancer risk overall, by menopausal and estrogen receptor (ER) status among 1,582 AA (749 cases) and 1,434 EA (744 cases) women using data from a case-control study, the Women's Circle of Health Study. Unconditional multivariable logistic regression models were used to compute odds ratios (ORs) and 95% confidence intervals (CIs) for the association of each nutrient and breast cancer risk. In AA women, inverse associations were observed for natural food folate intake among premenopausal women (fourth vs. first quartile: OR = 0.57, 95% CI, 0.33-1.00; p for trend = 0.06) and for ER-positive tumors (fourth vs. first quartile: OR = 0.58, 95% CI, 0.36-0.93; p for trend = 0.03), whereas in EA women, a positive association was observed for intake of synthetic folate (fourth vs. first quartile: OR = 1.53, 95% CI, 1.06-2.21; p for trend = 0.03). Our findings suggest that natural food folate intake is inversely associated with breast cancer risk and that this association may vary by race, menopausal status or ER status. The finding of an increased risk observed among EA women with the highest intake of synthetic folate from fortified foods warrants further investigation.

High levels of folate from supplements and fortification are not associated with increased risk of colorectal cancer

BACKGROUND & AIMS

Folate intake has been inversely associated with colorectal cancer risk in several prospective epidemiologic studies. However, no study fully assessed the influence of the high levels of folate that are frequently consumed in the United States as a result of mandatory folate fortification, which was fully implemented in 1998, and the recent increase in use of folate-containing supplements. There is evidence that consumption of high levels of folic acid, the form of folate used for fortification and in supplements, has different effects on biochemical pathways than natural folates and might promote carcinogenesis.

METHODS

We investigated the association between folate intake and colorectal cancer among 43,512 men and 56,011 women in the Cancer Prevention Study II (CPS-II) Nutrition Cohort; 1023 were diagnosed with colorectal cancer between 1999 and 2007, a period entirely after folate fortification began. Cox proportional hazards regression was used to calculate multivariate hazards ratios (RR) and 95% confidence interval (CI).

RESULTS

Intake of high levels of natural folate (RRQ5vsQ1=0.86; 95% CI: 0.70-1.06; P trend=.12) or folic acid (RRQ5vsQ1=0.84; 95% CI: 0.68-1.03; P trend=.06) were not significantly associated with risk of colorectal cancer. Total folate intake was significantly associated with lower risk (RRQ5vsQ1=0.81; 95% CI: 0.66-0.99; P trend=.047).

CONCLUSIONS

Intake of high levels of total folate reduces risk of colorectal cancer; there is no evidence that dietary fortification or supplementation with this vitamin increases colorectal cancer risk.

High dietary niacin intake is associated with decreased chromosome translocation frequency in airline pilots

Experimental studies suggest that B vitamins such as niacin, folate, riboflavin, vitamin B6 and vitamin B12 may protect against DNA damage induced by ionising radiation (IR). However, to date, data from IR-exposed human populations are not available. We examined the intakes of these B vitamins and their food sources in relation to the frequency of chromosome translocations as a biomarker of cumulative DNA damage, in eighty-two male airline pilots. Dietary intakes were estimated by using a self-administered semi-quantitative FFQ. Translocations in peripheral blood lymphocytes were scored by using fluorescence in situ hybridisation whole-chromosome painting. Negative binomial regression was used to estimate rate ratios and 95 % CI, adjusted for age and occupational and lifestyle factors. We observed a significant inverse association between translocation frequency and dietary intake of niacin (P = 0·02): adjusted rate ratio for subjects in the highest tertile compared with the lowest tertile was 0·58 (95 % CI 0·40, 0·83). Translocation frequency was not associated with total niacin intake from food and supplements as well as dietary or total intake of folate, riboflavin or vitamin B6 or B12. However, the adjusted rate ratios were significant for subjects with ≥ median compared with < median intake of whole grains (P = 0·03) and red and processed meat (P = 0·01): 0·69 (95 % CI 0·50, 0·96) and 1·56 (95 % CI 1·13, 2·16), respectively. Our data suggest that a high intake of niacin from food or a diet high in whole grains but low in red and processed meat may protect against cumulative DNA damage in IR-exposed persons.

Folate and other one-carbon metabolism-related nutrients and risk of postmenopausal breast cancer in the Cancer Prevention Study II Nutrition Cohort

BACKGROUND

Epidemiologic studies of the association of folate intake with breast cancer risk have been inconclusive, and few have investigated how related nutrients modify this association.

OBJECTIVE

We investigated the association of dietary (food folate plus folic acid from fortification) and total folate (food folate, folic acid from fortification, and folic acid from supplements), vitamin B-6, vitamin B-12, methionine, and alcohol intakes with postmenopausal breast cancer among women in the Cancer Prevention Study II Nutrition Cohort. The modification of the folate associations by the other nutrients was also investigated.

DESIGN

This prospective cohort study included 70,656 postmenopausal women for whom dietary information was collected in 1992. Of these, 3898 developed breast cancer between enrollment in 1992 and June 2005. Cox proportional hazards modeling was used to calculate multivariate-adjusted hazard rate ratios and 95% CIs.

RESULTS

Compared with the lowest quintile, the highest quintile of dietary folate intake was associated with a higher risk of breast cancer (rate ratio: 1.12; 95% CI: 1.01, 1.24). However, the test for trend was not significant (P for trend = 0.15). No association was found for total folate, vitamin B-6, or vitamin B-12, but methionine was inversely associated with breast cancer risk (P for trend = 0.04). The association of dietary folate with breast cancer was not modified by other nutrients or alcohol.

CONCLUSIONS

This study suggests that dietary folate intake may be positively associated with postmenopausal breast cancer. However, no dose-response relation was observed. The extent to which increased supplement use and folate fortification contributes to breast cancer risk warrants further research.

Folate bioavailability: implications for establishing dietary recommendations and optimizing status

The addition of folic acid to the US food supply, along with the critical role of folate in certain health outcomes, has intensified worldwide interest in the bioavailability of folate. Bioavailability is a function of absorptive and postabsorptive processes, which in turn are influenced by diet, individuality, and complex diet-host interactions. As such, it is unlikely that a single bioavailability figure will accurately reflect food folate bioavailability from every diet for every person. Although there is broad agreement that naturally occurring food folate is not as bioavailable as folic acid, questions remain as to the extent of these differences, particularly within the context of a whole diet. This article 1) summarizes and integrates bioavailability estimates derived from studies that use whole-diet approaches; 2) highlights the influences of genetics, ethnicity-race, and sex as postabsorptive bioavailability modifiers; and 3) discusses the adequacy of the US folate Recommended Dietary Allowance in achieving folate sufficiency in select subpopulations.

Fortification of Flour with Folic Acid

Background

After randomized, controlled trials established that consumption of folic acid before pregnancy and during the early weeks of gestation reduces the risk of a neural tube defect (NTD)-affected pregnancy, the United States Public Health Service recommended in 1992 that all women capable of becoming pregnant consume 400 μg folic acid daily. In 1998, folic acid fortification of all enriched cereal grain product flour was fully implemented in the United States and Canada.

Objective

To provide guidance on national fortification of wheat and maize flours to prevent 50 to 70% of the estimated 300,000 NTD-affected pregnancies worldwide.

Methods

An expert workgroup reviewed the latest evidence of effectiveness of folic acid flour fortification and the safety of folic acid.

Results

Recent estimates show that in the United States and Canada, the additional intake of about 100 to 150 μg/day of folic acid through food fortification has been effective in reducing the prevalence of NTDs at birth and increasing blood folate concentrations in both countries. Most potential adverse effects associated with folic acid are associated with extra supplement use not mandatory fortification. Fortification of wheat flour has a proven record of prevention in other developed countries. In 2009, 51 countries had regulations written for mandatory wheat flour fortification programs that included folic acid.

Conclusions

NTDs remain an important cause of perinatal mortality and infantile paralysis worldwide. Mandatory fortification of flour with folic acid has proved to be one of the most successful public health interventions in reducing the prevalence of NTD-affected pregnancies. Most developing countries have few, if any, common sources of folic acid, unlike many developed countries, which have folic acid available from ready-to-eat cereals and supplements. Expanding the number of developed and developing countries with folic acid flour fortification has tremendous potential to safely eliminate most folic acid-preventable NTDs.

Serum folate and cancer mortality among U.S. adults: findings from the Third National Health and Nutritional Examination Survey linked mortality file

BACKGROUND

The relation between folate status and cancer is controversial. Several epidemiologic studies have suggested that increased folate intake is associated with reduced risk of various cancers, others have found no such associations, and a few have suggested that high folate intake might increase the risk of certain cancers.

METHODS

Using data from the Third National Health and Nutrition Examination Survey (NHANES III) Mortality File, a prospective cohort study of a nationally representative sample of 14,611 U.S. adults, we conducted Cox proportional hazards regression modeling to investigate the association of baseline serum folate concentrations and all-cancer mortality determined from linked death certificate data.

RESULTS

Relative to the lowest quintile of serum folate (<3.0 ng/mL), the multivariable-adjusted hazard ratios across quintiles 2 to 5 were: 1.61 [95% confidence interval (95% CI), 1.11-2.32], 1.00 (95% CI, 0.65-1.49), 1.39 (95% CI, 0.96-2.03), and 0.85 (95% CI, 0.59-1.22). These findings did not differ substantially by age or sex, but the higher risk for those in the second quintile appeared limited to non-Hispanic whites.

CONCLUSION

These findings suggest that there may be a nonlinear relationship between folate status and the risk of all-cancer mortality such that persons with low, but not grossly deficient, serum blood folate concentrations may be at increased risk. Further study is needed to determine whether these findings are due to chance, and if not, to clarify their biological basis.

Folate intake, methylenetetrahydrofolate reductase polymorphisms, and breast cancer risk in women from the Malmö Diet and Cancer cohort

BACKGROUND

Single nucleotide polymorphisms (SNP) of the folate-metabolizing enzyme methylenetetrahydrofolate reductase (MTHFR) may modify associations between folate intake and breast cancer. We examined if the association between tertiles of dietary folate equivalents (DFE) and breast cancer was different in subgroups according to genotypes of the MTHFR 677 C>T (rs1801133) and 1298A>C (rs1801131) SNPs and if the polymorphisms per se were associated with breast cancer.

METHODS

This nested case-control study included 544 incident cases with invasive breast cancer and 1,088 controls matched on age and blood sampling date from the population-based Malmö Diet and Cancer cohort. Genotyping of the MTHFR SNPs was done with PCR-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Odds ratios (OR) were obtained by unconditional logistic regression.

RESULTS

DFE was positively associated with breast cancer in MTHFR 677CT/TT-1298AA women (P for trend = 0.01) but inversely associated in compound heterozygous women (P for trend = 0.01). Interaction was observed between DFE and the 1298C allele (P = 0.03). The 677T allele was associated with increased breast cancer risk in women above 55 years [multivariate adjusted OR, 1.34; 95% confidence interval (95% CI), 1.01-1.76] and an interaction was observed between the T allele and age (P = 0.03). Homozygosis for the 1298C allele was associated with increased risk in women between 45 and 55 years (multivariate adjusted OR, 1.89; 95% CI, 1.09-3.29).

CONCLUSION

In conclusion, a positive association between DFE and breast cancer was observed in MTHFR 677CT/TT-1298AA women but an inverse association was observed in 677CT-1298AC women. The 677T allele was associated with higher breast cancer risk in women above 55 years of age.

Steady state folate concentrations achieved with 5 compared with 1.1 mg folic acid supplementation among women of childbearing age

BACKGROUND

Synthetic folic acid (0.4-1.0 mg) consumed during the periconceptional period has been shown to reduce the risk of neural tube defects. Women with poor supplement adherence or a previous pregnancy affected by a neural tube defect may need to take higher doses of folic acid (4-5 mg). However, there are limited data on the pharmacokinetics of higher folic acid doses.

OBJECTIVE

Our aim was to compare steady state folate concentrations in women of childbearing age who took 5 or 1.1 mg folic acid daily for 30 wk.

DESIGN

Forty nonpregnant women aged between 18 and 45 y, who did not take folic acid supplements, were enrolled in the study. Subjects were randomly assigned to take either 5 or 1.1 mg folic acid daily for 30 wk. Plasma and red blood cell (RBC) folate concentrations were measured at baseline and at weeks 2, 4, 6, 12, and 30.

RESULTS

There was no significant difference in baseline RBC folate concentrations between the 2 groups (1121 +/- 410 and 1035 +/- 273 nmol/L for the 5- and 1.1-mg folic acid groups, respectively). Significant differences in RBC folate were detected between groups at weeks 4, 6, 12, and 30. RBC folate concentrations by week 30 were 2339 +/- 782 and 1625 +/- 339 nmol/L for the 5- and 1.1-mg folic acid groups, respectively.

CONCLUSION

The use of 5 mg folic acid among women of childbearing age produced higher blood folate concentrations, with a faster rate of folate accumulation, compared with 1.1 mg folic acid.

Causes of Vitamin B12 and Folate Deficiency

This review describes current knowledge of the main causes of vitamin B12 and folate deficiency. The most common explanations for poor vitamin B12 status are a low dietary intake of the vitamin (i.e., a low intake of animal-source foods) and malabsorption. Although it has long been known that strict vegetarians (vegans) are at risk for vitamin B12 deficiency, evidence now indicates that low intakes of animal-source foods, such as occur in some lacto-ovo vegetarians and many less-industrialized countries, cause vitamin B12 depletion. Malabsorption of the vitamin is most commonly observed as food-bound cobalamin malabsorption due to gastric atrophy in the elderly, and probably as a result of Helicobacter pylori infection. There is growing evidence that gene polymorphisms in transcobalamins affect plasma vitamin B12 concentrations. The primary cause of folate deficiency is low intake of sources rich in the vitamin, such as legumes and green leafy vegetables, and the consumption of these foods may explain why folate status can be adequate in relatively poor populations. Other situations in which the risk of folate deficiency increases include lactation and alcoholism.

Folate intake at RDA levels is inadequate for Mexican American men with the methylenetetrahydrofolate reductase 677TT genotype

Since the establishment of the 1998 folate recommended dietary allowance (RDA), the methylenetetrahydrofolate reductase (MTHFR) 677C-->T variant has emerged as a strong modifier of folate status. This controlled feeding study investigated the adequacy of the RDA, 400 microg/d as dietary folate equivalents (DFE), for Mexican American men with the MTHFR 677CC or TT genotype. Because of the interdependency between folate and choline, the influence of choline intake on folate status was also assessed. Mexican American men (n = 60; 18-55 y) with the MTHFR 677CC (n = 31) or TT (n = 29) genotype consumed 438 microg DFE/d and total choline intakes of 300, 550 (choline adequate intake), 1100, or 2200 mg/d for 12 wk. Folate status response was assessed via serum folate (SF), RBC folate, plasma total homocysteine (tHcy), and urinary folate. SF decreased (P < 0.001) 66% to 7.9 +/- 0.7 nmol/L (means +/- SEM) in men with the 677TT genotype and 62% to 11.3 +/- 0.9 nmol/L in the 677CC genotype. Plasma tHcy increased (P < 0.0001) 170% to 31 +/- 3 micromol/L in men with the 677TT genotype and 18% to 11.6 +/- 0.3 micromol/L in the 677CC genotype. At the end of the study, 34% (677TT) and 16% (677CC) had SF concentrations <6.8 nmol/L and 79% (677TT) and 7% (677CC) had tHcy concentrations >14 micromol/L. Choline intake did not influence the response of the measured variables. These data showed that the folate RDA is not adequate for men of Mexican descent, particularly for those with the MTHFR 677TT genotype, and demonstrated a lack of influence of choline intake on the folate status variables measured in this study.

Dietary intake of folate, but not vitamin B2 or B12, is associated with increased bone mineral density 5 years after the menopause: results from a 10-year follow-up study in early postmenopausal women

Folate, vitamin B2 (riboflavin), and vitamin B12 may affect bone directly or through an effect on plasma homocysteine levels. Previously, a positive association has been found between plasma levels and bone mineral density (BMD) as well as risk of fracture. However, there are limited data on whether dietary intakes affect bone. Our aim was to investigate whether intake of folate, vitamin B2) and vitamin B12, as assessed by food records affects BMD and fracture risk. In a population-based cohort including 1,869 perimenopausal women from the Danish Osteoporosis Prevention Study, associations between intakes and BMD were assessed at baseline and after 5 years of follow-up. Moreover, associations between intakes and 5- and 10-year changes in BMD as well as risk of fracture were studied. Intakes of folate, vitamin B2, and vitamin B12 were 417 (range 290-494) microg/day, 2.70 (range 1.70-3.16) mg/day, and 4.98 (range 3.83-6.62) microg/day, respectively, i.e., slightly above the intakes recommended by the United Nations Food and Agriculture Organization. At year 5, but not at baseline, cross-sectional analyses showed positive correlations between daily intake from diet and from diet plus supplements of folate and BMD at the femoral neck (P < 0.01). However, no associations were found between intakes and changes in BMD. During 10 years of follow-up, 360 subjects sustained a fracture. Compared with 1,440 controls, logistic regression analyses revealed no difference in intakes between cases and controls. A high dietary intake of folate, but not vitamin B2 or B12, exerts positive effects on BMD; but further studies are needed to confirm this association.

Reassessing folic acid consumption patterns in the United States (1999 2004): potential effect on neural tube defects and overexposure to folate

BACKGROUND

In the United States, folic acid fortification of cereal- grain foods has significantly increased folate status. However, blood folate concentrations have decreased from their postfortification high as a result, in part, of decreasing food fortification concentrations and the popularity of low-carbohydrate weight-loss diets.

OBJECTIVES

The objectives of the study were to quantify changes in folate intake after folic acid fortification and to estimate the effect on neural tube defect (NTD) occurrence.

DESIGN

Expanding on an earlier model, we used data from 11 intervention studies to determine the relation between chronic folate intervention and changes in steady state serum folate concentrations. With serum folate data from the National Health and Nutrition Examination Survey (NHANES), we used reverse prediction to calculate postfortification changes in daily folate equivalents (DFEs). With the use of NHANES red blood cell folate data and a published equation that related NTD risk to maternal red cell folate concentrations, we calculated NTD risk.

RESULTS

Folate intake decreased by approximately 130 microg DFE/d from its postfortification high, primarily as a result of changes seen in women with the highest folate status. This decrease in folate intake was predicted to increase the incidence of NTD by 4-7%, relative to a predicted 43% postfortification decrease. In addition, the number of women consuming >1 mg bioavailable folate/d decreased.

CONCLUSIONS

Folate consumption by women of childbearing age in the United States has decreased. However, the decrease in those women with the lowest folate status was disproportionately small. Consequently, the effect on NTD risk should be less than would be seen if a uniform decrease in folate concentrations had occurred. These results reinforce the need to maintain monitoring of the way fortification is implemented.

How well do blood folate concentrations predict dietary folate intakes in a sample of Canadian lactating women exposed to high levels of folate? An observational study

Background

In 1998, mandatory folic acid fortification of white flour and select cereal grain products was implemented in Canada with the intention to increase dietary folate intakes of reproducing women. Folic acid fortification has produced a dramatic increase in blood folate concentrations among reproductive age women, and a reduction in neural tube defect (NTD)-affected pregnancies. In response to improved blood folate concentrations, many health care professionals are asking whether a folic acid supplement is necessary for NTD prevention among women with high blood folate values, and how reliably high RBC folate concentrations predict folate intakes shown in randomized controlled trials to be protective against NTDs. The objective of this study was to determine how predictive blood folate concentrations and folate intakes are of each other in a sample of well-educated lactating Canadian women exposed to high levels of synthetic folate.

Methods

The relationship between blood folate concentrations and dietary folate intakes, determined by weighed food records, were assessed in a sample of predominantly university-educated lactating women (32 ± 4 yr) at 4-(n = 53) and 16-wk postpartum (n = 55).

Results

Median blood folate concentrations of all participants were well above plasma and RBC folate cut-off levels indicative of deficiency (6.7 and 317 nmol/L, respectively) and all, except for 2 subjects, were above the cut-off for NTD-risk reduction (>906 nmol/L). Only modest associations existed between total folate intakes and plasma (r = 0.46, P < 0.001) and RBC (r = 0.36, P < 0.01) folate concentrations at 16-wk postpartum. Plasma and RBC folate values at 16-wk postpartum correctly identified the quartile of folate intake of only 26 of 55 (47%) and 18 of 55 (33%) of subjects, respectively. The mean RBC folate concentration of women consuming 151–410 μg/d of synthetic folate (2^nd quartile of intake) did not differ from that of women consuming >410 μg/d (3^rd and 4^th quartile).

Conclusion

Folate intakes, estimated by food composition tables, and blood folate concentrations are not predictive of each other in Canadian lactating women exposed to high levels of folate. Synthetic intakes > 151–410 μg/d in these women produced little additional benefit in terms of maximizing RBC content. More studies are needed to examine the relationship between blood folate concentration and NTD risk. Until data from such studies are available, women planning a pregnancy should continue to consume a daily folic acid supplement of 400 μg.

High folate intake is associated with lower breast cancer incidence in postmenopausal women in the Malmö Diet and Cancer cohort

BACKGROUND

Epidemiologic studies of associations between folate intake and breast cancer are inconclusive, but folate and other plant food nutrients appear protective in women at elevated risk.

OBJECTIVE

The objective was to examine the association between folate intake and the incidence of postmenopausal breast cancer.

DESIGN

This prospective study included all women aged >or=50 y (n = 11699) from the Malmö Diet and Cancer cohort. The mean follow-up time was 9.5 y. We used a modified diet-history method to collect nutrient intake data. At the end of follow-up, 392 incident invasive breast cancer cases were verified. We used proportional hazard regression to calculate hazard ratios (HRs).

RESULTS

Compared with the lowest quintile, the incidence of invasive breast cancer was reduced in the highest quintile of dietary folate intake (HR: 0.56; 95% CI: 0.35, 0.90; P for trend = 0.02); total folate intake, including supplements (HR: 0.56; 95% CI: 0.34, 0.91; P for trend = 0.006); and dietary folate equivalents (HR: 0.59; 95% CI: 0.36, 0.97; P for trend = 0.01).

CONCLUSION

A high folate intake was associated with a lower incidence of postmenopausal breast cancer in this cohort.

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.

Additional food folate derived exclusively from natural sources improves folate status in young women with the MTHFR 677 CC or TT genotype

The effectiveness of additional food folate in improving folate status in humans is uncertain particularly in people with the common genetic variant (677 C-->T) in the methylenetetrahydrofolate reductase (MTHFR) gene. To examine the effect of a doubling of food folate consumption on folate status response variables, women (n=32; 18-46 years) with the MTHFR 677 CC or TT genotype consumed either 400 (n=15; 7 CC and 8 TT) or 800 (n=17; 8 CC and 9 TT) microg/day of dietary folate equivalents (DFE) derived exclusively from naturally occurring food folate for 12 weeks. A repeated measures two-factor ANOVA was used to examine the effect of the dietary treatment, the MTHFR C677T genotype and their interactions on serum folate, RBC folate and plasma total homocysteine (tHcy) during the last 3 weeks of the study. Consumption of 800 microg DFE/day resulted in serum folate concentrations that were 67% (P=.005) higher than consumption of 400 microg DFE/day (18.6+/-2.9 vs. 31.0+/-2.7 nmol/L, respectively) and RBC folate concentrations that were 33% (P=.001) higher (1172+/-75 vs. 1559+/-70 nmol/L, respectively). Serum folate (P=.065) and RBC folate (P=.022) concentrations were lower and plasma tHcy was higher (P=.039) in women with the MTHFR 677 TT genotype relative to the CC genotype. However, no genotype by dietary treatment interaction was detected. These data suggest that a doubling of food folate intake will lead to marked improvements in folate status in women with the MTHFR 677 CC or TT genotype.

The glycine N-methyltransferase (GNMT) 1289 C->T variant influences plasma total homocysteine concentrations in young women after restricting folate intake

Glycine N-methyltransferase (GNMT) is a key regulatory protein in folate metabolism, methionine availability, and transmethylation reactions. Perturbations in GNMT may lead to aberrations in homocysteine metabolism, a marker of numerous pathologies. The primary objective of this study was to examine the influence of the GNMT 1289 C-->T alone, and in combination with the methylenetetrahydrofolate reductase (MTHFR) 677 C-->T variant, on plasma total homocysteine concentrations in healthy young women (n = 114). Plasma total homocysteine was measured at baseline (wk 0) and after 2 wk of controlled folate restriction (135 microg/d as dietary folate equivalents). Plasma homocysteine concentrations did not differ among the GNMT C1289T genotypes at baseline. However, after folate restriction, women with the GNMT 1289 TT genotype (n = 16) had higher (P = 0.019) homocysteine concentrations than women with the CT (n = 51) or CC (n = 47) genotype. The influence of the GNMT 1289 C-->T variant on homocysteine was dependent on the MTHFR C677T genotype. In subjects with the MTHFR 677 CC genotype, homocysteine was greater (P < or = 0.05) for GNMT 1289 TT subjects relative to 1289 CT or CC subjects. However, in subjects with the MTHFR 677 TT genotype, plasma homocysteine concentrations did not differ among the GNMT C1289T genotypes. Overall, these data suggest that the GNMT 1289 C-->T polymorphism influences plasma homocysteine and is responsive to folate intake.

Research goals for folate and related B vitamin in Europe

In the past decade, the understanding of folate bioavailability, metabolism and related health issues has increased, but several problems remain, including the difficulty of delivering the available knowledge to the populations at risk. Owing to the low compliance of taking folic acid supplements, for example, among women of child-bearing age who could lower the risk of having a baby with a neural tube defect, food-based strategies aimed at increasing the intake of folate and other B-group vitamins should be a priority for future research. These should include the development of a combined strategy of supplemental folate (possibly with vitamin B(12)), biofortification using engineered plant-derived foods and micro-organisms and food fortification for increasing folate intakes in the general population. Currently, the most effective population-based strategy to reduce NTDs remains folic acid fortification. However, the possible adverse effect of high intakes of folic acid on neurologic functioning among elderly persons with vitamin B(12) deficiency needs urgent investigation. The results of ongoing randomized controlled studies aimed at reducing the prevalence of hyperhomocysteinemia and related morbidity must be available before food-based total population approaches for treatment of hyperhomocysteinemia can be recommended. Further research is required on quantitative assessment of folate intake and bioavailability, along with a more thorough understanding of physiological, biochemical and genetic processes involved in folate absorption and metabolism.