Plasma folate as marker of folate status in epidemiological studies: the European Investigation into Cancer and Nutrition (EPIC)-Potsdam study

Methods and approaches to estimate B vitamin status in dairy cows: Knowledge, gaps and advances

Clinical symptoms of B vitamin deficiency are rarely observed in ruminants because these vitamins are synthesized by the rumen microbiota. However, over the last decades, numerous reports of beneficial effects on production and metabolic efficiency of dairy cows have been published supporting that, under some conditions, B vitamin subclinical deficiency is present in these animals. Due to their roles as coenzymes or cofactors in major metabolic pathways, an adequate supply in B vitamins is critical to optimize metabolic efficiency. Nowadays, taking into account the growing interest for the Smart Farming concept, fulfilling ruminant requirements for B vitamins according to their physiological stage under different feeding management cannot be neglected. In dairy cows, B vitamin supply is greatly dependent of the activity of the ruminal microbiota. Indeed, the amount of vitamins reaching the small intestine is dependent of the utilization of the vitamins provided by the diet and their synthesis by the microorganisms present in the rumen. The two major challenges faced to determine B vitamin status of ruminants are the difficulty to estimate B vitamin supply due to the lack of knowledge on factors driving the fate of B vitamins in the digestive tract, especially in the rumen, and the choice and thresholds of biomarkers reflecting adequately the animal status. The present paper aims to present the actual state of knowledge on the methodological approaches used to estimate B vitamin supply and status of ruminant and to point out future research orientations.

Validation of a food frequency questionnaire as a tool for assessing dietary intake in cardiovascular disease research and surveillance in Bangladesh

BACKGROUND

Cardiovascular disease (CVD) has emerged as a major public health concern in Bangladesh. Diet is an established risk factor for CVD but a tool to assess dietary intake in Bangladesh is lacking. This study aimed to validate a food frequency questionnaire (FFQ) using the 24-h dietary recall method and corresponding nutritional biological markers among rural and urban populations of Bangladesh.

METHOD

Participants of both genders aged 18-60 years were included in the analysis (total n = 146, rural n = 94 and urban n = 52). Two FFQs of 166 items were administered three-months apart, during which time three 24-h dietary recalls were also completed. Participants were asked to recall their frequency of consumption over the preceding 3 months. Urine and blood samples were collected for comparison between FFQ-estimates of nutrients and their corresponding biomarkers. Methods were compared using unadjusted, energy-adjusted, de-attenuated correlation coefficients, 95% limits of agreement (LOA) and quartile classification.

RESULTS

Fair to moderate agreement for ranking energy, macro and micronutrients into quartiles was observed (weighted k value ranged from 0.22 to 0.58; p < 0.001 for unadjusted data) except for vitamin D (weighted k - 0.05) and zinc (weighted k 0.09). Correlation coefficients of crude energy, macronutrients and common micronutrients including vitamin E, thiamine, riboflavin, niacin, pyridoxine, folate, iron, magnesium, phosphorus, potassium, and sodium were moderately good, ranging from 0.42 to 0.78; p < 0.001 but only fair for vitamin A, β carotene and calcium (0.31 to 0.38; p < 0.001) and poor for vitamin D and zinc (0.02 and 0.16; p = ns, respectively). Energy-adjusted correlations were generally lower except for fat and vitamin E, and in range of - 0.017 (for calcium) to 0.686 (for fat). De-attenuated correlations were higher than unadjusted and energy- adjusted, and significant for all nutrients except for vitamin D (0.017) to 0.801 (for carbohydrate). The Bland Altman tests demonstrated that most of the coefficients were positive which indicated that FFQ provided a greater overestimation at higher intakes. More than one in three participants appeared to overestimate their food consumption based on the ratio of energy intake to basal metabolic rate cut points suggested by Goldberg. Absolute intake of macronutrients was 1.5 times higher and for micronutrients it ranged from 1.07 (sodium) to 26 times (Zinc). FFQ estimates correlated well for sodium (0.32; p < 0.001), and vitamin D (0.20; p = 0.017) with their corresponding biomarkers and iron (0.25; p = 0.003) with serum ferritin for unadjusted data. Folate, iron (with haemoglobin) and total protein showed inverse association; and fat and potassium showed poor correlation with their corresponding biomarkers for unadjusted data. However, folate showed significant positive correlation (0.189; p = 0.025) with biomarker after energy adjustment.

CONCLUSION

Although FFQ showed overestimation for absolute intake in comparison with 24-h recalls, the validation study demonstrated acceptable agreement for ranking dietary intakes from FFQ with 24-h recall methods and some biomarkers and therefore could be considered as a tool to measure dietary intake for research and CVD risk factors surveillance in Bangladesh. The instrument may not be appropriate for monitoring population adherence to recommended intakes because of the overestimation.

One-carbon metabolism biomarkers and risk of urothelial cell carcinoma in the European prospective investigation into cancer and nutrition

Published associations between dietary folate and bladder cancer risk are inconsistent. Biomarkers may provide more accurate measures of nutrient status. This nested case-control analysis within the European Prospective Investigation into Cancer and Nutrition (EPIC) investigated associations between pre-diagnostic serum folate, homocysteine, vitamins B6 and B12 and the risk of urothelial cell carcinomas of the bladder (UCC). A total of 824 patients with newly diagnosed UCC were matched with 824 cohort members. Serum folate, homocysteine, and vitamins B6 and B12 were measured. Odds ratios (OR) and 95% confidence intervals (CI) for total, aggressive, and non-aggressive UCC were estimated using conditional logistic regression with adjustment for smoking status, smoking duration and intensity, and other potential confounders. Additionally, statistical interaction with smoking status was assessed. A halving in serum folate concentrations was moderately associated with risk of UCC (OR: 1.18; 95% CI: 0.98-1.43), in particular aggressive UCC (OR: 1.34; 95% CI: 1.02-1.75; p-heterogeneity = 0.19). Compared to never smokers in the highest quartile of folate concentrations, this association seemed only apparent among current smokers in the lowest quartile of folate concentrations (OR: 6.26; 95% CI: 3.62-10.81, p-interaction = 0.07). Dietary folate was not associated with aggressive UCC (OR: 1.26; 95% CI: 0.81-1.95; p-heterogeneity = 0.14). No association was observed between serum homocysteine, vitamins B6 and B12 and risk of UCC. This study suggests that lower serum folate concentrations are associated with increased UCC risk, in particular aggressive UCC. Residual confounding by smoking cannot be ruled out and these findings require confirmation in future studies with multiple measurements.

Systematic Review of Observational Studies with Dose-Response Meta-Analysis between Folate Intake and Status Biomarkers in Adults and the Elderly

BACKGROUND

Dietary reference values for folate intake vary widely across Europe.

METHODS

MEDLINE and Embase through November 2016 were searched for data on the association between folate intake and biomarkers (serum/plasma folate, red blood cell [RBC] folate, plasma homocysteine) from observational studies in healthy adults and elderly. The regression coefficient of biomarkers on intake (β) was extracted from each study, and the overall and stratified pooled β and SE (β) were obtained by random effects meta-analysis on a double log scale. These dose-response estimates may be used to derive folate intake reference values.

RESULTS

For every doubling in folate intake, the changes in serum/plasma folate, RBC folate and plasma homocysteine were +22, +21, and -16% respectively. The overall pooled regression coefficients were β = 0.29 (95% CI 0.21-0.37) for serum/plasma folate (26 estimates from 17 studies), β = 0.28 (95% CI 0.21-0.36) for RBC (13 estimates from 11 studies), and β = -0.21 (95% CI -0.31 to -0.11) for plasma homocysteine (10 estimates from 6 studies).

CONCLUSION

These estimates along with those from randomized controlled trials can be used for underpinning dietary recommendations for folate in adults and elderly.

Assessing Volumetric Absorptive Microsampling Coupled with Stable Isotope Dilution Assay and Liquid Chromatography-Tandem Mass Spectrometry as Potential Diagnostic Tool for Whole Blood 5-Methyltetrahydrofolic Acid

Volumetric absorptive microsamplers (VAMS) have been developed recently as a promising tool for clinical blood sampling. Compared to dried blood spot samples analyzed by accurate stable isotope dilution assays (SIDAs), the new technique could provide further substantial miniaturizing of folate assays by eliminating hematocrit effects and uneven analyte distribution within the sample. Herein, we present a miniaturized SIDA coupled with LC-MS/MS measurement of 5-methyltetrahydrofolic acid as main folate vitamer in whole blood (WB) using [13C5]-5-methyltetrahydrofolic acid as internal standard. Elution and extraction of only 10.8 μL-dried WB were carried out by centrifugation followed by enzymatic treatment for polyglutamate deconjugation. Matrix separation was achieved by heating and centrifugation. To verify applicability, WB folate status of 11 volunteers was screened. Limits of detection and limits of quantitation were 9 and 26 nmol·L-1, respectively, which is sufficiently low for screening folate status. Recoveries were 97 (±5.8), 99 (±2.8), and 96 (±6.1)% for 800, 400, and 200 nmol L-1 5-methyltetrahydrofolic acid, respectively. Precision of the LC-MS/MS instrument and inter-assay precision trials revealed CVs of 8.1 and 3.5% (294 nmol L-1), respectively, thus confirming reproducible and precise quantitation. Compared to fresh WB, no significant degradation of 5-methyltetrahydrofolate was observed after 2.5 h of drying at room temperature. VAMS 5-CH3-H4folate was stable for at least 3 weeks at -20°C. In our pilot study, accurate and diagnostically conclusive determination of folate status was verified. Nevertheless, blood sampling should be performed by trained individuals to avoid substantial errors concerning the absorbed volume. Endogenous folate in rat serum and chicken pancreas caused a significant background especially at low blood 5-CH3-H4folate levels and, thus, for polyglutamate deconjugation, these background folates or alternative mixtures need to be removed. The superior feasibility of a minimized blood collection with VAMS allows further progress regarding time- and cost-effective methodologies in newborn or population screenings for 5-methyltetrahydrofolate status. Further steps toward minimization could include an automated assay coupled with UPLC-MS/MS.

Predictors of folate status among pregnant Japanese women: the Hokkaido Study on Environment and Children’s Health, 2002–2012

The International Clearinghouse for Birth Defects, Surveillance and Research reports a rise in the prevalence rate of spina bifida in Japan. We determined first-trimester folate status of Hokkaido women and identified potential predictors. Participants were 15 266 pregnant women of the Hokkaido Study on Environment and Children’s Health Cohort. Data were extracted from self-reported questionnaires and biochemical assay results. Demographic determinants of low folate status were younger maternal age (adjusted OR (AOR) 1·48; 95 % CI 1·32, 1·66), lower educational level (AOR 1·27; 95 % CI 1·17, 1·39) and lower annual income (AOR 1·11; 95 % CI 1·01, 1·22). Plasma cotinine concentrations of 1·19–65·21 nmol/l increased the risk of low folate status (AOR 1·20; 95 % CI 1·10, 1·31) and concentrations >65·21 nmol/l further increased the risk (AOR 1·91; 95 % CI 1·70, 2·14). The most favourable predictor was use of folic acid (FA) supplements (AOR 0·19; 95 % CI 0·17, 0·22). Certain socio-demographic factors influence folate status among pregnant Japanese women. Modifiable negative and positive predictors were active and passive tobacco smoking and use of FA supplements. Avoiding both active and passive tobacco smoking and using FA supplements could improve the folate status of Japanese women.

High serum folate might have a potential dual effect on risk of colorectal cancer

BACKGROUND & AIMS

The possible dual role of serum folate in the development and progression of colorectal cancer (CRC) has not been well established in human studies. This study investigated the association between serum folate and the risk of CRC in subjects with CRC or colorectal adenomatous polyps (AP, a precursor of CRC), and healthy subjects.

METHODS

This study has a case-control design. Two hundred and thirty-seven men and 171 women were recruited with 156 subjects in the CRC group, 70 subjects in the AP group and 182 healthy subjects in the control group.

RESULTS

The risk of CRC was significantly increased in the third (OR, 3.46; 95% CI, 1.16-10.34) and fourth (OR, 4.86; 95% CI, 1.42-16.58) quartiles of serum folate concentration after adjusting for potential confounders among subjects with AP or CRC. Furthermore, serum folate concentration had no significant effect on the risk of CRC among subjects in the control and CRC groups.

CONCLUSIONS

Higher serum folate concentration was significantly correlated with increased CRC risk in subjects with AP, while serum folate had no effect on CRC risk in healthy controls. Serum folate might possess potential dual modulatory effects on the risk of CRC.

Low folate levels are associated with reduced risk of colorectal cancer in a population with low folate status

BACKGROUND

A diet rich in folate is associated with a reduced colorectal cancer risk, whereas the role of circulating levels is less clear. The aim of this study was to relate prediagnostic plasma folate, vitamin B12, and homocysteine concentrations to the risk of colorectal cancer.

METHODS

This was a prospective case-control study of 331 cases and 662 matched controls nested within the population-based Northern Sweden Health and Disease Study. Median follow-up time from recruitment to diagnosis was 10.8 years.

RESULTS

Plasma folate concentrations were positively related to colorectal cancer risk; multivariate odds ratios were 1.62 [95% confidence intervals (CI), 1.08-2.42] and 1.42 (95% CI, 0.94-2.21) for the middle and highest versus lowest tertile, respectively. In subjects with follow-up <10.8 years, a statistically significant doubled risk was observed for the middle and highest versus lowest tertile, whereas findings for longer follow-up times were null. A positive risk relationship was also observed for tumor stage III-IV but not I-II. Plasma vitamin B12 concentrations were inversely associated with rectal cancer risk. Homocysteine was not significantly related to colorectal cancer risk.

CONCLUSIONS

In this population-based, nested case-control study, low plasma folate concentrations were associated with a reduced colorectal cancer risk. This protective role was mainly observed in subjects with higher tumor stage or shorter follow-up time between recruitment and diagnosis. Low circulating folate status may protect against colorectal cancer or suppress progression of preneoplastic or neoplastic lesions.

IMPACT

These findings may have relevance for the ongoing debate about mandatory folic acid fortification of flour.

Use of food frequency questionnaire to assess relationships between dietary habits and cardiovascular risk factors in NESCAV study: validation with biomarkers

BACKGROUND

Validation of Food frequency questionnaire (FFQ) is particularly important element, as incorrect information may lead to false associations between dietary factors and diseases. The aim of the study was to evaluate the validity of the FFQ used in NESCAV (Nutrition, Environment and Cardiovascular Health) study, by comparing the estimated intakes of fruits and vegetables and of several micro-nutrients with corresponding nutritional biomarkers.

METHODS

Relative validity was assessed in a sample of 922 subjects (452 men and 470 women). Comparisons between FFQ-estimates and their corresponding biomarkers were performed through correlation and cross classification into quintiles by using both crude and energy-adjusted FFQ-estimates. Correlations adjusted for confounders were also computed. All analyses were performed separately for men and women.

RESULTS

Concerning micro-nutrients, significant correlations were found for vitamin B9, D, E, B12 β-carotene and iodine in both men and women. Energy-adjustment led to an increase of all correlations cited previously. However, after excluding supplement users, correlations for vitamin D were not significant anymore. Concerning fruits and vegetables, all correlations were significant. Vegetables alone and fruits and vegetables correlated better in men (r around 0.2) than in women (r around 0.1). In men, correlation was also better for vegetables alone and fruits and vegetables than fruits alone.

CONCLUSION

These data demonstrate that this FFQ is a reasonable tool to assess intakes of fruits and vegetables and of several micro-nutrients. We conclude that our FFQ is suitable to be used in NESCAV study, although protein and vitamin D estimates should be interpreted with caution.

Plasma B vitamins and LINE-1 DNA methylation in leukocytes of patients with a history of colorectal adenomas

SCOPE

Low concentrations of folate, other B vitamins, and methionine are associated with colorectal cancer risk, possibly by changing DNA methylation patterns. Here, we examine whether plasma concentrations of B vitamins and methionine are associated with methylation of long interspersed nuclear element-1 (LINE-1) among those at high risk of colorectal cancer, i.e. patients with at least one histologically confirmed colorectal adenoma (CRA) in their life.

METHODS AND RESULTS

We used LINE-1 bisulfite pyrosequencing to measure global DNA methylation levels in leukocytes of 281 CRA patients. Multivariable linear regression was used to assess associations between plasma B vitamin concentrations and LINE-1 methylation levels. Plasma folate was inversely associated with LINE-1 methylation in CRA patients, while plasma methionine was positively associated with LINE-1 methylation.

CONCLUSION

This study does not provide evidence that in CRA patients, plasma folate concentrations are positively related to LINE-1 methylation in leukocytes but does suggest a direct association between plasma methionine and LINE-1 methylation in leukocytes.

Micronutrient intake and status in Central and Eastern Europe compared with other European countries, results from the EURRECA network

Objective

To compare micronutrient intakes and status in Central and Eastern Europe (CEE) with those in other European countries and with reference values.

Design

Review of the micronutrient intake/status data from open access and grey literature sources from CEE.

Setting

Micronutrients studied were folate, iodine, Fe, vitamin B12 and Zn (for intake and status) and Ca, Cu, Se, vitamin C and vitamin D (for intake). Intake data were based on validated dietary assessment methods; mean intakes were compared with average nutrient requirements set by the Nordic countries or the US Institute of Medicine. Nutritional status was assessed using the status biomarkers and cut-off levels recommended primarily by the WHO.

Subjects

For all population groups in CEE, the mean intake and mean/median status levels were compared between countries and regions: CEE, Scandinavia, Western Europe and Mediterranean.

Results

Mean micronutrient intakes of adults in the CEE region were in the same range as those from other European regions, with exception of Ca (lower in CEE). CEE children and adolescents had poorer iodine status, and intakes of Ca, folate and vitamin D were below the reference values.

Conclusions

CEE countries are lacking comparable studies on micronutrient intake/status across all age ranges, especially in children. Available evidence showed no differences in micronutrient intake/status in CEE populations in comparison with other European regions, except for Ca intake in adults and iodine and Fe status in children. The identified knowledge gaps urge further research on micronutrient intake/status of CEE populations to make a basis for evidence-based nutrition policy.

Dietary assessment methods for micronutrient intake: a systematic review on vitamins

The EURRECA Network of Excellence is working towards the development of aligned micronutrient recommendations across Europe. The purpose of the present study was to define how to identify dietary intake validation studies in adults pertaining to vitamins. After establishing a search strategy, we conducted a MEDLINE and EMBASE literature review. A scoring system was developed to rate the quality of each validation study according to sample size, statistical methods, data collection procedure, seasonality and vitamin supplement use. This produced a quality index with possible scores obtained ranging from 0.5 to 7. Five thousand four-hundred and seventy-six papers were identified. The numbers meeting the inclusion criteria were: for vitamin A, 76; vitamin C, 108; vitamin D, 21; vitamin E, 75; folic acid, 47; vitamin B12, 19; vitamin B6, 21; thiamine, 49; riboflavin, 49; and niacin, 32. The most frequently used method to ascertain dietary intake was the Food Frequency Questionnaire (FFQ), whereas dietary records (DR) and 24-h recalls were the most used reference methods. The correlation coefficients (CC) between vitamin intakes estimated by FFQ and the reference method were weighted according to the study's quality index and ranged from 0.41 to 0.53 when the reference method was the DR and from 0.43 to 0.67 when the reference was 24-h recalls. A minority of studies (n 33) used biomarkers for validation and in these the CC ranged from 0.26 to 0.38. The FFQ is an acceptable method of assessing vitamin intake. The present review provides new insights regarding the characteristics that assessment methods for dietary intake should fulfil.

A U-shaped relationship between plasma folate and pancreatic cancer risk in the European Prospective Investigation into Cancer and Nutrition

Folate intake has shown an inverse association with pancreatic cancer; nevertheless, results from plasma measurements were inconsistent. The aim of this study is to examine the association between plasma total homocysteine, methionine, folate, cobalamin, pyridoxal 5'-phosphate, riboflavin, flavin mononucleotide and pancreatic cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC). We conducted a nested case-control study in the EPIC cohort, which has an average of 9.6 years of follow-up (1992-2006), using 463 incident pancreatic cancer cases. Controls were matched to each case by center, sex, age (± 1 year), date (± 1 year) and time (± 3 h) at blood collection and fasting status. Conditional logistic regression was used to calculate the odds ratios (OR) and 95% confidence intervals (CI), adjusting for education, smoking status, plasma cotinine concentration, alcohol drinking, body mass index and diabetes status. We observed a U-shaped association between plasma folate and pancreatic cancer risk. The ORs for plasma folate ≤ 5, 5-10, 10-15 (reference), 15-20, and > 20 nmol/L were 1.58 (95% CI=0.72-3.46), 1.39 (0.93-2.08), 1.0 (reference), 0.79 (0.52-1.21), and 1.34 (0.89-2.02), respectively. Methionine was associated with an increased risk in men (per quintile increment: OR=1.17, 95% CI=1.00-1.38) but not in women (OR=0.91, 95% CI=0.78-1.07; p for heterogeneity <0.01). Our results suggest a U-shaped association between plasma folate and pancreatic cancer risk in both men and women. The positive association that we observed between methionine and pancreatic cancer may be sex dependent and may differ by time of follow-up. However, the mechanisms behind the observed associations warrant further investigation.

Use of a food frequency questionnaire to assess diets of Jamaican adults: validation and correlation with biomarkers

Background

Assessment of habitual diet is important in investigations of diet-disease relationships. Many epidemiological studies use the food frequency questionnaire (FFQ) to evaluate dietary intakes but few studies validate the instrument against biological markers. The aim of this study was to assess the validity and reproducibility of a previously validated 70-item food frequency questionnaire (FFQ) that was expanded to 120-items to assess diet - cancer relations.

Methods

Relative validity of the FFQ was assessed against twelve 24-hour recalls administered over 12 months in 70 subjects. The FFQ was repeated after one year (FFQ2) to assess reproducibility. The validity of the FFQ was evaluated by comparing nutrient and food group intakes from 24-hour recalls with the first and second FFQ. In addition, FFQ validity for cholesterol and folate were determined through correlation with biomarkers (serum cholesterol, serum folate and whole blood folate) in 159 control subjects participating in a case-control prostate cancer study.

Results

Compared to recalls the FFQ tended to overestimate energy and carbohydrate intakes but gave no differences in intake for protein and fat. Quartile agreement for energy-adjusted nutrient intakes between FFQ2 and recalls ranged from 31.8% - 77.3% for the lowest quartile and 20.8% - 81.0% in the highest quartile. Gross misclassification of nutrients was low with the exceptions of protein, vitamin E and retinol and weighted kappa values ranged from 0.33 to 0.64 for other nutrients. Validity correlations for energy-adjusted nutrients (excluding retinol) were moderate to high (0.38- 0.86). Correlation coefficients between multiple recalls and FFQ1 ranged from 0.27 (fruits) to 0.55 (red meat); the second FFQ gave somewhat higher coefficients (0.30 to 0.61). Reproducibility correlations for the nutrients ranged from 0.50 to 0.84.

Calibration of the FFQ with biochemical markers showed modest correlations with serum cholesterol (0.24), serum folate (0.25) and whole blood folate (0.33) adjusted for age, energy, body mass index and smoking.

Conclusions

The expanded FFQ had good relative validity for estimating food group and nutrient intakes (except retinol and vitamin E) and was a reliable measure of habitual intake. Associations with biomarkers were comparable to other studies.

Folate and cobalamin status in relation to diet in healthy 2-y-old children

BACKGROUND

Limited data exist on sources of folate and cobalamin in the toddler diet.

OBJECTIVE

We examined the influence of diet on folate and cobalamin status in healthy toddlers in an unfortified population.

DESIGN

Dietary intake was assessed in 178 children, aged 24 mo, by using 7-d food records and related to serum folate and cobalamin status in 155 children.

RESULTS

Median (25th-75th percentile) daily intakes of folate and cobalamin were 87 μg (74-104 μg) and 3.1 μg (2.4-3.8 μg), respectively. Thirty-five percent of subjects had a folate intake below the Norwegian recommendations (80 μg folate/d), but only 5.8% of subjects had low serum folate concentrations (<10 nmol/L). All children reached the recommended cobalamin intake (0.8 μg cobalamin/d). Median (25th-75th percentile) serum concentrations were as follows: folate, 19 nmol/L (14-24 nmol/L); cobalamin, 410 pmol/L (334-521 pmol/L); holotranscobalamin, 94 pmol/L (67-121 pmol/L); holohaptocorrin, 315 pmol/L (241-409 pmol/L); methylmalonic acid, 0.16 μmol/L (0.13-0.20 μmol/L); and total homocysteine, 5.0 μmol/L (4.2-5.7 μmol/L). Folate intake correlated with serum folate concentrations (ρ = 0.25, P < 0.01), and cobalamin intake correlated with serum holotranscobalamin concentrations (ρ = 0.21, P < 0.05). In multivariate models, serum folate concentrations were significantly positively associated with the consumption of fruit and berries and grain products; however, this was not the case with dairy products, which was the food group that contributed most to folate intake. Cobalamin status was associated with dairy products (cobalamin and holotranscobalamin), cobalamin supplements (cobalamin and holohaptocorrin), and liver pâté (holotranscobalamin).

CONCLUSIONS

In this unfortified toddler population, folate status was associated with intakes of fruit and berries and grain products. Cobalamin status was associated with intakes of dairy, liver pâté, and supplements. In the assessment of vitamin sources, vitamin availability must be considered.

Plasma folate concentrations are positively associated with risk of estrogen receptor beta negative breast cancer in a Swedish nested case control study

Folate's role in breast cancer development is controversial. Not only estrogen receptor (ER) alpha status, but also ERbeta status of tumors may have confounded results from previous epidemiological studies. We aimed to examine associations between plasma folate concentration and postmenopausal breast cancer defined by ER status. This nested case-control study, within the Malmö diet and cancer cohort, included 204 incident breast cancer cases with information on ERalpha and ERbeta status determined by immunochemistry on tissue micro-array sections. Plasma folate concentration was analyzed for the cases and 408 controls (matched on age and blood sample date). Odds ratios (OR) for ER-defined breast cancers in tertiles of plasma folate concentration were calculated with unconditional logistic regression. All tests were 2-sided. Women in the third tertile of plasma folate concentration (> 12 nmol/L) had higher incidence of ERbeta- breast cancer than women in the first tertile (OR: 2.67; 95% CI: 1.44-4.92; P-trend = 0.001). We did not observe significant associations between plasma folate concentration and other breast cancer subgroups defined by ER status. We observed a difference between risks for ERbeta + and ERbeta- cancer (P-heterogeneity = 0.003). Our findings, which indicate a positive association between plasma folate and ERbeta- breast cancer, highlight the importance of taking ERbeta status into consideration in studies of folate and breast cancer. The study contributes knowledge concerning folate's multifaceted role in cancer development. If replicated in other populations, the observations may have implications for public health, particularly regarding folic acid fortification.

Validity of food frequency questionnaire estimated intakes of folate and other B vitamins in a region without folic acid fortification

BACKGROUND/OBJECTIVES

B vitamins have been implicated in major chronic diseases but results have been inconsistent. This study evaluated the accuracy of dietary intakes of folate, vitamin B12, riboflavin and vitamin B6 as measured by the Northern Sweden Food Frequency Questionnaire (FFQ) against repeated 24-h recalls (24HR) and plasma levels, taking into consideration the MTHFR 677C>T polymorphism.

SUBJECTS/METHODS

B vitamin intakes assessed by a semi-quantitative FFQ designed to measure the intake over the previous year were compared with those from 10 24HR, as well as to plasma levels of folate and vitamin B12, in randomly selected men (n=96) and women (n=99) aged 30-60 years. FFQ-based B-vitamin intakes were also compared with plasma levels of B-vitamins and with MTHFR 677C4T genotype in 878 men, aged 40-61 years.

RESULTS

Intakes of vitamins B12 and riboflavin were similar, whereas folate and B6 intakes were 16-27% higher, as estimated by FFQ versus 24HR. Spearman correlation coefficients between the two methods ranged from 0.31 to 0.63 (all P<or=0.002), and were lowest for vitamin B12. Intakes estimated by FFQ were correlated with plasma levels, but coefficients were lower (range: 0.13-0.33), particularly for vitamin B12 in men (0.15-0.18). Folate intake was not correlated with plasma levels in subjects with the MTHFR 677 T/T genotype.

CONCLUSIONS

The validity of the Northern Sweden FFQ for assessing B vitamin intake is similar to that of many other FFQs used in large-scale studies. The FFQ is suitable for ranking individuals by intake of folate, riboflavin, vitamin B6 and to a lesser extent vitamin B12.

Serum folate is a reliable indicator of hyperhomocysteinemia and borderline hyperhomocysteinemia in young adults

Serum folate has been shown to correlate well with fasting plasma homocysteine; however, erythrocyte folate concentration is a better index of tissue folate stores and probably could be a more reliable indicator for reflecting long-term supply of the vitamin and homocysteine status. The present study was undertaken to test the hypothesis that serum folate and erythrocyte folate levels had a different degree of correlation to fasting plasma homocysteine in young Taiwanese adults. This study had a cross-sectional design. Healthy young adults were divided into either a hyperhomocysteinemia (HHcy; > or =14.9 micromol/L; n = 13), borderline HHcy (BHcy; fasting homocysteine, 14.9-10.2 micromol/L; n = 52), or normohomocysteinemia (fasting homocysteine, <10.2 micromol/L; n = 65) groups based on fasting homocysteine levels. The concentrations of plasma fasting homocysteine, serum folate, erythrocyte folate, vitamin B(12), and plasma pyridoxal 5'-phosphate were measured. Fasting homocysteine was only significantly and inversely affected by serum folate (beta = -0.21, P < .05) concentration after adjusting for potential confounders. Only serum folate concentration remained to decrease the risk of fasting HHcy (odds ratio, 0.73; confidence interval, 0.56-0.95) after the other B vitamins were additionally adjusted. Serum folate also had the highest area under the receiver operating characteristic (AUC) curve to predict the risk of HHcy (AUC, 0.81) and BHcy (AUC, 0.77). Serum folate is a reliable indicator of fasting hyperhyperhomocysteinemia and BHcy in young adults.

Increased breast cancer risk at high plasma folate concentrations among women with the MTHFR 677T allele

BACKGROUND

Folate is involved in DNA synthesis and methylation and may thereby influence carcinogenesis.

OBJECTIVES

We examined plasma folate (P-folate) concentration in relation to genotypes of the folate-metabolizing enzyme methylenetetrahydrofolate reductase [MTHFR 677C-->T (rs1801133) and 1298A-->C (rs1801131)]. We also explored whether P-folate was associated with risk of postmenopausal breast cancer overall and in subgroups with genetic variants of the MTHFR single nucleotide polymorphisms (SNPs).

DESIGN

This nested case-control study included 313 cases (age 55-73 y at baseline) with invasive breast cancer and 626 control subjects, matched on age and blood-sample date, from the population-based Malmö Diet and Cancer cohort. P-folate and MTHFR genotypes were determined for 310 cases and 611 controls. P-folate according to genotype was calculated by using analysis of variance. Odds ratios were obtained by using logistic regression. All tests were 2-sided.

RESULTS

The variant 677T allele was associated with lower P-folate. In women with the 677T allele, a high P-folate concentration was associated with increased breast cancer risk (P for trend across P-folate tertiles = 0.03). Interaction was seen between the 677C-->T SNP and P-folate (P = 0.002). A positive association, which was seen between P-folate and breast cancer risk in 1298AA women (P = 0.01), was probably due to linkage between the 2 SNPs. Overall, and in women with other genotypes, no significant associations were observed.

CONCLUSIONS

Our results suggest an association of high P-folate concentration with increased risk of postmenopausal breast cancer in carriers of the 677T allele. The findings underline the importance of genetic variation of MTHFR in the complex relation between folate and cancer.

Folate status of Ghanaian populations in London and Accra

Migration to the UK is associated with higher incidence of stroke in African populations. A low folate status has been associated with increased risk of stroke, likely to be mediated through raised plasma homocysteine concentrations. We conducted a cross-sectional study to compare blood folate and homocysteine concentrations in eighty healthy Ghanaian migrants living in London matched by sex, age and occupation to 160 individuals from an urban population in Accra, Ghana. Folate intake was determined using three 24 h recalls. Fasting blood samples were collected for the determination of serum and erythrocyte folate and plasma homocysteine concentrations and the methylenetetrahydrofolate reductase (MTHFR) 677C → T polymorphism. Reported mean folate intake was 20 % lower in London compared with Accra (P < 0·001). However, serum folate was 44 % higher, erythrocyte folate 30 % higher and plasma homocysteine was 26 % lower in subjects from London compared with those from Accra (P < 0·001). These differences persisted after adjusting for confounders including the MTHFR 677C → T mutation, which was rare in both populations. Although there were no associations between dietary folate intake and blood folates (P>0·05), folic acid supplement use, which was more prevalent in London than Accra (25 and 10 %, respectively,P = 0·004) was associated with erythrocyte folate in both populations (P < 0·01). The main predictors of plasma homocysteine concentrations were erythrocyte folate and male sex (P < 0·001). Findings from the present study suggest that migration from Ghana to the UK results in improvement of biomarkers of folate status despite the fact that reported dietary intake of folate was apparently lower in subjects from London.

Plasma folate and total homocysteine levels are associated with the risk of myocardial infarction, independently of each other and of renal function

OBJECTIVES

To investigate the relationship between plasma folate, vitamin B12 and total homocysteine concentrations, dietary intake of folate and vitamins B12, B6 and B2, and the risk of first acute myocardial infarction (MI).

DESIGN

Nested case-referent study with up to 13 years of follow-up.

SETTING

The population-based Northern Sweden Health and Disease Study, with 73 879 participants at the time of case ascertainment.

SUBJECTS

A total of 571 MI cases (406 men) and 1569 matched referents. Of the cases, 530 had plasma samples available, and 247 had dietary B-vitamin intake data.

RESULTS

Plasma concentrations of folate were inversely associated, and total homocysteine positively associated, with the risk of MI, independently of each other and of a number of established and novel cardiovascular risk factors, including renal function [multivariate odds ratio for highest vs. lowest quintile of folate 0.52 (95% CI 0.31-0.84), P for trend = 0.036, and homocysteine 1.92 (95% CI 1.20-3.09), P for trend = 0.006]. For plasma vitamin B12 concentrations, and vitamin B12, B6 and B2 intake, no clear risk relationship was apparent. Though not statistically significant, the results for folate intake were consistent with those for plasma concentrations.

CONCLUSIONS

In this large prospective study of a population without mandatory folic acid fortification, both folate and homocysteine were strongly associated with the risk of myocardial infarction, independently of each other and of renal function. Although randomized trials of folic acid supplementation are needed to determine causality, our findings highlight the potential importance of folate, or sources of folate, in incident cardiovascular disease.

The reduced folate carrier (RFC1) 80G > A and folate hydrolase 1 (FOLH1) 1561C > T polymorphisms and the risk of colorectal cancer: a nested case-referent study

OBJECTIVE

Polymorphisms in genes involved in folate uptake and metabolism may affect folate status and, thereby, the risk of cancer. In this nested case-referent study, we related two such polymorphisms, reduced folate carrier (RFC1) 80G > A and folate hydrolase 1 (FOLH1) 1561C > T, to the risk of colorectal cancer, taking into account pre-diagnostic plasma folate and total homocysteine concentrations and the MTHFR 677C > T polymorphism, which were analysed in a previous study.

MATERIAL AND METHODS

Subjects were 220 cases and 414 matched referents from the population-based Northern Sweden Health and Disease Study.

RESULTS

The RFC1 80A-allele was associated with reduced plasma folate and elevated plasma total homocysteine concentrations, but the result was statistically significant only for folate. In contrast, the FOLH1 1561T-allele was associated with higher plasma folate and reduced plasma total homocysteine concentrations, and the result was statistically significant only for homocysteine. Neither polymorphism was related to the risk of colorectal cancer, either in univariate analysis or after adjusting for body mass index, current smoking, recreational and occupational physical activity and alcohol intake. Further adjustment for folate or homocysteine status or the MTHFR 677C > T polymorphism did not affect risk estimates. Subjects with the RFC1 80AA genotype in combination with low plasma folate concentrations or the MTHFR 677TT genotype had a reduced risk of colorectal cancer of borderline statistical significance.

CONCLUSIONS

These findings suggest that although the RFC1 80G > A and FOLH1 1561C > T polymorphisms may influence folate status, they are not likely to have a major independent role in the development of colorectal cancer.

Methods to evaluate the effect of ethanol on the folate analogue: fluorescein methotrexate uptake in human proximal tubular cells

Ethanol-induced folate deficiency is due to effects of ethanol on folate metabolism and absorption. We have already shown by using different methods that ethanol interferes with reabsorption of folate from the proximal tubule. In this study, we have used the folate analogue, the fluorescein methotrexate (FL-MTX), in order to evaluate effects of ethanol on FL-MTX uptake by the human proximal tubular (HPT) cells by using a confocal microscope and fluoroskan microplate reader. Since endothelins (ETs) play a major role in a number of diseases and also in the damage induced by a variety of chemicals, we have used endothelin-B (ET-B) and protein kinase-C (PKC) inhibitors to evaluate the role of endothelin in ethanol-mediated FL-MTX uptake by using fluoroskan microplate reader. Confocal microscope and fluoroskan studies reveal that cellular absorption of FL-MTX is concentration-dependent. Moreover, ethanol concentration has an impact on FL-MTX uptake. Fluoroskan studies reveal that the ethanol-induced decrease in FL-MTX uptake is reversed by adding the ET-B receptor antagonist (RES-701-1) or PKC-selective inhibitor (BIM). Thus, we can conclude that ethanol may act via ET and ET in turn may act via ET-B receptor and the PKC signaling pathway to impair FL-MTX transport.

Photodegradation of 5-methyltetrahydrofolate in the presence of Uroporphyrin

The main form of folate in human plasma is 5-methyltetrahydrofolate (5MTHF). The observation that folate in human serum is photosensitive supports the hypothesis that humans developed dark skin in high ultraviolet fluences areas in order to protect folate in the blood from UV radiation. However, folates alone are quite photostable. Therefore, in this study, we examined for the first time the photodegradation of 5MTHF in the presence of the endogenous photosensitizer uroporphyrin (Uro), which is sometimes present in low concentration in human serum, under UV and near-UV light exposure. We found strong indications that while 5MTHF alone is rather photostable, it is degraded quickly in the presence of Uro. Using deuterium oxide (D(2)O) as an enhancer of the lifetime of singlet oxygen and the singlet oxygen sensor green reagent (SOSG) as a scavenger of singlet oxygen, we have found that the photodegradation most likely proceeds via a type II photosensitization. Our results show that singlet oxygen is likely to be the main intermediate in the photodegradation of 5MTHF mediated by Uro. Our findings may be useful for further studies the evolution of human skin colours.

Gas chromatography/tandem mass spectrometry analysis of alkylresorcinols in red blood cells

Erythrocyte alkylresorcinols (5-alkyl-1,3-dihydroxybenzenes) are potential biomarkers of wholegrain wheat and rye intake. However, their high-throughput quantitative analysis by gas chromatography/mass spectrometry (GC/MS) is hindered by the time-consuming sample preparation and, more importantly, by interfering compounds that still remain after sample cleanup. In the present work we describe a gas chromatography/tandem mass spectrometry (GC/MS/MS) method for the rapid and reliable quantification of alkylresorcinols in erythrocyte samples. The performance of the GC/MS/MS method is compared with that of GC/MS. The main characteristics of the method are: lower limits of detection: 2-10 microg/L standard solution; lower limits of quantification: 6-30 microg/L standard solution; linearity coefficients: 0.9611-0.9888; linear ranges: 2-20 microg/L in erythrocytes; and intra-day precisions (n = 6): 4-13% at endogenous analyte levels in non-spiked erythrocytes. Tandem mass spectrometry showed greatly improved selectivity over single-stage mass spectrometry in the case of erythrocyte samples, eliminating all interferences detectable in single-stage MS and enabling simple peak integration for quantification. Moreover, increased selectivity resulted in GC separation speeded up by a factor of two, allowing the duplicate analysis of over 40 samples per day. This GC/MS/MS method is suggested as an improved alternative to GC/MS for the quantification of alkylresorcinols in erythrocytes for assessing wholegrain wheat and rye intake.

Prediagnostic plasma folate and the risk of death in patients with colorectal cancer

PURPOSE

Although previous studies have demonstrated an inverse relationship between folate intake and colorectal cancer risk, a recent trial suggests that supplemental folic acid may accelerate tumorigenesis among patients with a history of colorectal adenoma. Therefore, high priority has been given to research investigating the influence of folate on cancer progression in patients with colorectal cancer.

PATIENTS AND METHODS

To investigate whether prediagnostic levels of plasma folate are associated with colorectal cancer-specific and overall mortality, we performed a prospective, nested observational study within two large US cohorts: the Nurses' Health Study and Health Professionals Follow-Up Study. We measured folate levels among 301 participants who developed colorectal cancer 2 or more years after their plasma was collected and compared participants using Cox proportional hazards models by quintile of plasma folate.

RESULTS

Higher levels of plasma folate were not associated with an increased risk of colorectal cancer-specific or overall mortality. Compared with participants in the lowest quintile of plasma folate, those in the highest quintile experienced a multivariable-adjusted hazard ratio for colorectal cancer-specific mortality of 0.42 (95% CI, 0.20 0.88) and overall mortality of 0.46 (95% CI, 0.24 0.88). When the analysis was limited to participants whose plasma was collected within 5 years of cancer diagnosis, no detrimental effect of high plasma folate was noted. In subgroup analyses, no subgroup demonstrated worse survival among participants with higher plasma folate levels.

CONCLUSION

In two large prospective cohorts, higher prediagnostic levels of plasma folate were not associated with an increased risk of colorectal cancer-specific or overall mortality.

Validation of a food frequency questionnaire to assess folate intake of Dutch elderly people

Folate is required for 1-carbon metabolism and deficiency in folate leads to megaloblastic anemia. Low levels of folate have been associated with increased risk of vascular disease. To investigate whether RDA of folate are met, habitual folate intake needs to be assessed reliably. We developed a FFQ to specifically measure folate intake over the previous 3 months in elderly people in the Netherlands. Major sources of folate intake, i.e. foods contributing to at least 80 % of the average folate intake, were identified through an analysis of the second Dutch Food Consumption Survey for the sub-population of men and women aged 50–70. In 2000 and 2001, folate intake was estimated with this questionnaire in 1286 individuals aged 50–75 years. Concentrations of serum and erythrocyte folate served as biomarkers with which relative validity of the questionnaire was assessed. The same FFQ was repeated after 3 years in 803 subjects in order to assess long-term reproducibility. Mean folate intake was estimated to be 196 (sd 69) μg/d. Spearman correlation coefficients between folate intake and serum and erythrocyte concentrations were 0·14 (P < 0·01) and 0·05 (P = 0·06) respectively. Spearman correlations between folate intakes measured at baseline and after 3 years were 0·58 (P < 0·01). 47 % of the participants were classified in the same quartiles on the two occasions. Our FFQ showed a weak correlation between folate intake and blood folate concentrations and reproducibility was acceptable. This FFQ is able to rank subjects according to their folate intake.

Role of MTHFR polymorphisms and folate levels in different phenotypes of sporadic colorectal cancers

BACKGROUND AND AIMS

By altering both DNA methylation and nucleotide synthesis, folate metabolism is thought to contribute to colorectal carcinogenesis. We examined the role of folate metabolism in three different phenotypes of sporadic colorectal cancers (CRCs), phenotypes that were classified by the status of microsatellite instability (MSI) and chromosomal instability (CIN): MSI-H, microsatellite stability (MSS)/aneuploidy, and MSS/diploid.

PATIENTS AND METHODS

A total of 195 sporadic colorectal tumors and another 195 age- and gender-matched healthy volunteers in Taipei-Veteran General Hospital and Taipei City Hospital were collected. We analyzed for MTHFR (methylenetetrahydrofolate reductase) polymorphisms (C677T, A1297C), folate, and vitamin B(12) levels. We determined MSI status and DNA ploidy with fluorescent polymerase chain reaction and flow cytometry. Relations between clinicopathological variables and molecular variables were analyzed by chi (2) tests (with Yates' correction) for categorical variables and Student's t test for numerical variables.

RESULTS

Folate levels (5.02+/-4.43 ng/ml) were significantly lower in cancer patients than in controls (7.22+/-4.46 ng/ml). Vitamin B(12) level was similar between cancer patients and controls. The frequency of the TT genotype of MTHFR C627T (12.3%) was slightly higher than controls (8.2%), but it did not reach statistical significance (p=0.174). Within the low-folate group (<5 ng/ml), the frequency of the TT genotype in cancer patients (14.4%) was significantly higher than in controls (4.6%). Sixteen patients who had MSI-H CRC (8.2%) had a significantly higher frequency of TT MTHFR (37.5%) and lower folate levels (3.56+/-2.41 ng/ml) than patients with MSS tumors (10.1%, 5.14+/-3.72 ng/ml). Patients with MSS/aneuploid tumors had significantly lower folate levels (4.50+/-3.06 ng/ml) than those with MSS/diploid tumors (6.69+/-4.73 ng/ml).

CONCLUSION

Folate deficiency and the MTHFR genetic polymorphism play an important role in colorectal carcinogenesis, including MSI and CI.

SYNOPSIS

Folate metabolism plays an important role in colorectal carcinogenesis. We demonstrate that patients with MSI-H tumors had higher frequency of TT MTHFR C627T (37.5%), and patients with MSS/aneuploid tumor had lower folate level (4.50+/-3.06 ng/ml).

Dietary intake of B-vitamins, polymorphisms in thymidylate synthase and serine hydroxymethyltransferase 1, and colorectal adenoma risk: A Dutch case-control study

Thymidylate synthase and serine hydroxymethyltransferase are involved in folate metabolism. In a case-control study, including 768 cases and 709 controls, we investigated the associations between colorectal adenomas and TS tandem repeat and SHMT1 C1420T polymorphisms, and the interplay with B-vitamins. The polymorphisms were not associated with adenomas, but there was a borderline significant interaction between TS genotype and vitamin B6: the association between vitamin B6 and adenomas seemed positive in TS 3R/3R individuals, but inverse in TS 2R/2R individuals. This study does not provide evidence for a role of SHMT1 genotype in adenoma occurrence. Future research has to indicate whether the TS-B6 interplay is a real effect or a chance finding.

Dietary folate intake in combination with MTHFR C677T genotype and promoter methylation of tumor suppressor and DNA repair genes in sporadic colorectal adenomas

Methylation of the promoter region of tumor suppressor genes is increasingly recognized to play a role in cancer development through silencing of gene transcription. We examined the associations between dietary folate intake, MTHFR C677T genotype, and promoter methylation of six tumor suppressor and DNA repair genes. Patients with colorectal adenoma (n = 149) and controls (n = 286) with folate intake in the upper or lower tertile with the CC or TT genotype were selected from a case-control study. Methylation-specific PCRs were conducted on colorectal adenoma specimens. The percentages of promoter methylation ranged from 15.7% to 64.2%. In case-case comparisons, folate was inversely associated with promoter methylation, especially among TT homozygotes. Case-control comparisons suggested that folate was not associated with the occurrence of adenomas with promoter methylation, and increased the risk of unmethylated adenomas, especially in TT homozygotes. The interactions between folate and MTHFR genotype were most pronounced for O(6)-MGMT: compared with CC homozygotes with low folate intake, the adjusted odds ratios (95% confidence interval) of having a methylated O(6)-MGMT promoter were 3.39 (0.82-13.93) for TT homozygotes with low folate intake and 0.37 (0.11-1.29) for TT homozygotes with high folate intake (P interaction = 0.02); the odds ratios for the occurrence of adenomas without methylation were 0.57 (0.16-2.11) for TT homozygotes with low folate intake and 3.37 (1.17-9.68) for TT homozygotes with high folate intake (P interaction = 0.03). In conclusion, folate intake seems to be inversely associated with promoter methylation in colorectal adenomas in case-case comparisons, and was positively associated with the occurrence of adenomas without promoter methylation in case-control comparisons, especially for TT homozygotes.

Gene polymorphisms of folate metabolizing enzymes and the risk of gastric cancer

Multiple studies have reported an association between disturbances of folate metabolism and increased risk of gastric cancer, including low intake of folate, low levels of folate in blood or genetic factors affecting folate metabolism. Among the genetic factors, in particular a common polymorphism in the gene encoding for 5,10-methylenetetrahydrofolate reductase (MTHFR C677T) has been linked to gastric cancer. Other polymorphisms in folate-metabolising genes have been less frequently investigated. Therefore, we analyzed this polymorphism, the glutamate carboxypeptidase (GCP) II C1561T and the reduced folate carrier (RFC) G80A in a case-control study involving 106 patients with histologically confirmed and characterized gastric cancer with adjustment for other established risk factors for gastric cancer in comparison to 106 age- and sex-matched controls. Neither the MTHFR nor the GCP gene polymorphisms showed an association to cancer diagnosis, to tumor stage, grade of differentiation or Lauren type. However, non-cardia cancers were more likely to exhibit the 80GA and 80AA RFC genotypes, compared to cancers of the gastric cardia (adjusted OR 0.28; 95% CI=0.11-0.71). Thus, gene polymorphisms of the RFC gene might contribute to an increased risk of developing distal gastric cancer.

Preoperative folate and homocysteine status in patients undergoing major surgery

BACKGROUND & AIMS

Patients with folate deficiency and elevated homocysteine (Hcy) levels have increased risk of cerebrovascular and cardiovascular disease. They may also be at increased risk of complications after surgery because nitrous oxide interferes with folate metabolism. The aim of this study was to assess the incidence of folate deficiency and hyperhomocysteinemia in patients presenting for major surgery. We also tested the utility of a brief preoperative medical and dietary questionnaire to identify those with low folate or elevated Hcy levels.

METHODS

We enrolled 390 patients and obtained a preoperative fasting blood sample from each of the study participants (folate [n=386], homocysteine [n=387]).

RESULTS

Although only one patient had folate deficiency preoperatively (incidence +/-SD folate and Hcy concentrations were 23.7+/-5.2 nmol/l and 9.4+/-4.2 micromol/l, respectively. There was a negative correlation between folate and Hcy, r=-0.27, P<0.001. Multivariate analyses indicated that vegan status and folate supplementation prevented low folate status (P<0.05), while age of the patient, and history of heart failure and anaemia predicted elevated Hcy concentration.

CONCLUSIONS

Some factors identified by a brief medical and dietary questionnaire are associated with folate and homocysteine status. Hyperhomocysteinaemia occurs in about 7.5% of surgical patients; however, both low folate status and elevated Hcy concentration are less likely in those taking folate or vitamin B supplements. This has implications for patients undergoing nitrous oxide anaesthesia because of its inhibition of folate metabolism, and should prompt clinicians to consider folate and other nutritional supplementation before elective surgery.

Distinctive clinicopathological features of Ki-ras mutated colorectal cancers

BACKGROUND AND OBJECTIVES

We explored the relationship between the mutation pattern of Ki-ras and the clinicopathological features of colorectal cancers (CRCs).

METHODS

Relationships between clinicopathological parameters and Ki-ras mutation status were analyzed in 255 CRC patients using the chi-square and student t-tests. Kaplan-Meier survival curves were compared using the log-rank test.

RESULTS

Ki-ras mutation occurred in 43.9% of tumors, and 83% affected codon 12. The most frequent mutations were GGT->GAT (Gly->Asp) (37.5%), followed by GGT->GTT (Gly->Val) (31.3%), both in codon 12. The frequency of Ki-ras mutation was similar for different tumor stages (38.2-47.8%). The mucin component of tumors was significantly associated with Ki-ras mutation. The 4-year overall and disease-free survival was 61% and 54%, respectively, for patients with Ki-ras mutated tumors, and 73% and 60% for patients with nonmutated tumors (not statistically significant). Patients with Ki-ras mutated tumors had lower plasma folate (24 ng/dl) than those bearing nonmutated tumors (37 ng/dl). Patients with G->T Ki-ras mutations had the lowest folate level (22 ng/dl), followed by those with G->A mutations (25 ng/dl).

CONCLUSIONS

Ki-ras mutated colorectal tumors have a higher mucin production and higher differentiation, and are associated with lower plasma folate levels and a relatively poorer disease outcome.

Dietary and other lifestyle correlates of serum folate concentrations in a healthy adult population in Crete, Greece: a cross-sectional study

Background

Folate has emerged as a key nutrient for optimising health. Impaired folate status has been identified as a risk factor for cardiovascular disease, various types of cancers, and neurocognitive disorders. The study aimed at examining the distribution and determinants of serum folate concentrations in a healthy adult population in Crete, Greece.

Methods

A cross-sectional sample of 486 healthy adults (250 men, 236 women) aged 39 ± 14 years, personnel of the Medical School and the University Hospital of Crete in Greece, was examined. Serum folate and vitamin B₁₂ concentrations were measured by microbiological assay, and total homocysteine was determined fluorometrically and by high-pressure liquid chromatography. Lifestyle questionnaires were completed, and nutrient intakes and food consumption were assessed by 24-h dietary recalls. Multivariate analyses were performed using SPSS v10.1.

Results

The geometric mean (95% confidence interval) concentrations of serum folate were 15.6 μmol/l (14.6–16.8) in men and 19.2 μmol/l (17.9–20.7) in women (p < 0.001). Inadequate folate levels (≤7 nmol/l) were present in 6.8% of men and 2.1% of women (p < 0.001). Approximately 76% of men and 87% of women did not meet the reference dietary intake for folate (400 μg/day). Serum folate was inversely related to total homocysteine levels (p < 0.001). Increased tobacco and coffee consumption were associated with lower folate concentrations (p < 0.05 for both) but these associations disappeared after controlling for nutrient intakes. In multivariate analysis, intakes of MUFA, fibre, calcium, magnesium, folate, and vitamins A, E, C, B₁, and B₆ were positively associated with serum folate. Consumption of potatoes, legumes, fruits, and vegetables were favourably related to the serum folate status.

Conclusion

Serum folate concentrations were associated with various demographic, lifestyle and dietary factors in healthy Cretan adults. Large-scale epidemiological studies should be conducted within the general Greek adult population to assess the prevalence of impaired folate status and further examine associations with dietary patterns and chronic disease risk. Considering the importance of folate in health maintenance, it is important to increase the public's awareness of modifiable lifestyle patterns and diet and tobacco use in particular, which may be associated with improved folate status.

Dietary intake of folate and riboflavin, MTHFR C677T genotype, and colorectal adenoma risk: a Dutch case-control study

We investigated the associations between dietary intake of folate and vitamin B2, MTHFR C677T genotype, and colorectal adenomas in a Dutch case-control study. Data of cases with at least one histologically confirmed colorectal adenoma (n = 768) and controls with no history of any type of colorectal polyp (n = 709) were included. Dietary intake was assessed using a food-frequency questionnaire. Multivariable models included age and, if appropriate, dietary folate and calcium intake. The adjusted odds ratio (OR) and 95% confidence interval (CI) for the highest compared with the lowest sex-specific tertile of intake were 1.32 (95% CI, 1.01-1.73) for folate and 0.51 (95% CI, 0.36-0.73) for vitamin B2. Folate seemed to be a risk factor, especially when vitamin B2 intake was low; vitamin B2 was inversely associated with adenomas, especially with relatively high folate intake. No association was observed between MTHFR C677T genotype and colorectal adenomas. The inverse association between vitamin B2 intake and colorectal adenoma risk seemed to be more pronounced among those with the MTHFR TT genotype. We conclude that this study does not provide evidence for a decreased colorectal adenoma risk for subjects with high dietary intake of folate. It suggests, however, an inverse association between vitamin B2 and colorectal adenomas, which may be more relevant for those with the MTHFR TT genotype.

Folate, Vitamin B 12 , and Risk of Ischemic and Hemorrhagic Stroke

Background and Purpose— Folate metabolism has been implicated in stroke. However, the possibility of a role for folate and vitamin B 12 , independent of their effects on homocysteine status, remains to be explored. The aim of this prospective, nested case-referent study was to relate plasma and dietary intake levels of folate and vitamin B 12 to risk of stroke, taking into consideration plasma homocysteine concentrations and methylenetetrahydrofolate reductase polymorphisms.

Methods— Subjects were 334 ischemic and 62 hemorrhagic stroke cases and matched double referents from the population-based Northern Sweden Health and Disease Cohort.

Results— Plasma folate was statistically significantly associated with risk of hemorrhagic stroke in an inverse linear manner, both in univariate analysis and after adjustment for conventional risk factors including hypertension (odds ratio [OR] for highest versus lowest quartile 0.21 (95% confidence interval [CI], 0.06 to 0.71; P for trend=0.008)). Risk estimates were attenuated by inclusion of homocysteine in the model (OR, 0.34; 95% CI, 0.08 to 1.40; P for trend=0.088). A similar pattern was observed for increasing folate intake (multivariate OR, 0.07; 95% CI, 0.01 to 0.55; P for trend=0.031 without homocysteine, and OR, 0.16, 95% CI, 0.02 to 1.23; P for trend=0.118 with homocysteine in the analysis). We found little evidence of an association between plasma or dietary folate and risk of ischemic stroke. Neither plasma nor dietary vitamin B 12 was associated with risk of either stroke subtype.

Conclusions— The results of this study suggest a protective role for folate, possibly in addition to its effects on homocysteine status, in hemorrhagic but not ischemic stroke.