Serum folate concentrations and all-cause, cardiovascular disease and cancer mortality: A cohort study based on 1999-2010 National Health and Nutrition Examination Survey (NHANES)

Folate Biomarkers, Folate Intake, and Risk of Death From All Causes, Cardiovascular Disease, and Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies

CONTEXT

Existing evidence on the relation between folate intake and biomarkers with mortality risk is controversial.

OBJECTIVE

Previous cohort studies were examined regarding folate intake and biomarkers in relation to risk of all-cause, cardiovascular disease- (CVD), and cancer-related mortality through a systematic review and meta-analysis.

DATA SOURCES

A systematic search was performed of the PubMed, Scopus, and ISI Web of Science databases up to July 2023.

DATA EXTRACTION

Prospective cohort studies examining the association of folate biomarkers (in serum, plasma, red blood cells) and intake with risk of all-cause, CVD-, and cancer-related mortality were considered. A random-effects model was applied to combine study-specific risk estimates. Dose-response relations were assessed by 1-stage weighted mixed-effects meta-analysis.

DATA ANALYSIS

A total of 25 cohorts with 423 304 participants, 36 558 all-cause, 12 662 CVD-, and 2426 cancer-related deaths were included. No significant association was observed between the highest levels of folate biomarkers and all-cause mortality risk (hazard ratio [HR], 0.91; 95% CI, 0.77-1.06; n = 17; I2 = 89.4%; P < .001), CVD-related mortality risk (HR, 0.97; 95% CI, 0.87-1.06; n = 11; I2 = 0.0%; P = .57), and cancer-related mortality risk (HR, 0.85; 95% CI, 0.69-1.05; n = 6; I2 = 57.8%; P = .04) compared with the lowest. Furthermore, each 10 nmol/L increase was marginally related to a 12% reduced all-cause mortality risk but not to CVD- and cancer-related mortality risk. A significant inverse association was found between highest intake of dietary folate and the lowest, and risk of all-cause (HR, 0.87; 95% CI, 0.78-0.96; n = 3; I2 = 63.6%; P = .06) and CVD (HR, 0.77; 95% CI, 0.57-0.93; n = 4; I2 = 80.2%; P = .002) mortality.

CONCLUSIONS

This meta-analysis revealed a significant inverse relation between dietary folate intake and risk of all-cause and CVD mortality. Such an association was not found in the case of folate biomarkers. Further prospective studies are warranted to confirm these findings.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023401700.

Association of serum folate concentrations with cancer mortality among patients with arthritis: a prospective cohort study

BACKGROUND

Patients with arthritis exhibit abnormal serum folate concentrations and have a higher incidence of cancer. The aim of this study was to investigate the association of serum folate concentrations with cancer mortality among individuals with arthritis.

METHODS

This cohort study included 7,514 patients with arthritis from National Health and Nutrition Examination Survey (NHANES) 1999 to 2016 and NHANES III (1988-1994). Death outcomes were ascertained by linkage to National Death Index records through 31 December 2019. Serum folate concentrations were categorized into 4 groups, group 1 (≤ 17 nmol/L); group 2 (17-≤34 nmol/L); group 3 (34-≤51 nmol/L); and group 4 (> 51 nmol/L). Cox regression models were used to calculate hazard ratios and 95% confidence intervals for the associations between folate concentrations and the risk of mortality.

RESULTS

During a median follow-up of 9.75 [interquartile range, IQR, 5.75-14.5] years, there were 2,602 all-cause deaths, 949 deaths due to cardiovascular disease, and 478 deaths due to cancer. A non-linear association was observed for folate concentrations with the risk of cancer mortality (P < 0.001) among arthritis patients. Compared with the reference group 2, the hazard ratios for cancer mortality were 1.75 (95% CI, 1.15-2.69) in group 1, 1.70 (95% CI, 1.17-2.46) in group 3, and 1.60 (95% CI, 1.13-2.25) in group 4.

CONCLUSIONS

This study shows that both low and high levels of serum folate are associated with an increased risk of cancer mortality among individuals with arthritis, indicating a potential beneficial role of maintaining moderate serum folate concentrations in decreasing the risk of cancer mortality among this population.

Total IgE levels are associated with mortality risk partially mediated by vitamin status: A nationally representative population-based study

BACKGROUND AND AIMS

Elevated total IgE levels are traditionally associated with allergic conditions; however, their potential role as biomarker for mortality risk beyond allergic diseases has not been extensively explored. Recent studies have suggested that IgE is associated with cardiovascular (CV) disease. We aimed to investigate the association between total IgE levels and the risk of all-cause and cause-specific mortality, as well as to explore the potential mediating role of vitamin status in these associations.

METHODS AND RESULTS

The association between IgE and mortality risk was examined in the National Health and Examination Survey 2005-2006. Weighted multivariable Cox proportional hazards model was employed. We further performed restricted cubic spline analysis to assess dose-response relationships and conducted mediation analysis to explore the influence of vitamins on IgE-related mortality risk. Individuals in the highest total IgE quantile (>107.0 kU/L) exhibited a 32 % increased risk of all-cause mortality (95 % CI: 1.07-1.64) and a 98 % elevated risk of CV mortality (95 % CI: 1.28-3.07) compared to the lowest quantile (<14.5 kU/L). Heterogeneity exists in the dose-response relationship and threshold effects among individuals with and without allergic diseases. Vitamin deficiency is associated with elevated total IgE levels, and vitamins mediated the relationship of the IgE-related all-cause mortality with the proportion of mediation ranging from 4.68 to 12.71 %.

CONCLUSIONS

Our findings introduce a novel dimension to the understanding of IgE as a biomarker for mortality beyond its traditional role in allergic diseases, challenging the current paradigm that elevated IgE levels without overt allergic symptoms are benign.

Associations of serum folate and vitamin B12 levels with all-cause mortality among patients with metabolic dysfunction associated steatotic liver disease: a prospective cohort study

Introduction

Serum folate and vitamin B12 levels correlate with the prevalence of fatty liver disease, but it is not clear how they affect mortality. Therefore, this study aimed to investigate the association of serum folate and vitamin B12 concentrations with all-cause mortality in individuals with metabolic dysfunction-associated steatotic liver disease (MASLD).

Methods

MASLD subjects were from the Third National Health and Nutrition Examination Survey (NHANES III) in the United States, and mortality follow-up data were obtained by linkage to death records from the National Death Index. Multivariable Cox proportional regression models and restricted cubic spline (RCS) models were used to evaluate the association of serum folate/vitamin B12 with all-cause mortality in the MASLD population.

Results

3,636 and 2,125 MASLD individuals were included in the analyses related to serum folate and vitamin B12, respectively. During a follow-up period of more than 20 years, the RCS models demonstrated significant nonlinear associations of both serum folate (P <0.001) and vitamin B12 (P =0.016) with all-cause mortality in MASLD. When their serum concentrations were below the median level, the risk of all-cause mortality decreased with increasing concentration, reaching a lowest risk around the median level, and then leveled off. In the multivariable cox regression model, for vitamin B12, the risk of all-cause mortality was reduced by 42% and 28% in the third and fourth quartile groups, respectively, compared with the lowest quartile group (hazard ratio [HR]=0.58, 95% CI: 0.39-0.86, P =0.008; HR =0.72, 95% CI: 0.54-0.96, P=0.026, respectively). For folate, the risk of all-cause mortality was reduced by 28% in the third quartile compared with the lowest quartile (HR =0.72, 95% CI: 0.57-0.91, P =0.005).

Conclusion

This longitudinal cohort study suggests that low serum folate and vitamin B12 levels in patients with MASLD are significantly associated with an elevated risk of all-cause mortality.

Dietary folate intake and all-cause mortality and cardiovascular mortality in American adults with non-alcoholic fatty liver disease: Data from NHANES 2003 to 2018

BACKGROUND

The relationship between dietary folate intake and prior mortality in adult patients with Non-alcoholic Fatty Liver Disease (NAFLD) has not been clearly studied. We aimed to examine the relationship between dietary folate intake and all-cause and cardiovascular (CVD) mortality in adult NAFLD patients in the US.

METHODS

Using data from National Health and Nutrition Examination Survey (NHANES) 2003-2018 and associated mortality data we conducted a cohort study of US adult NAFLD subjects. Multivariable Cox proportional hazards regression models were used to evaluate the relationship between dietary folate intake and both all-cause mortality and CVD mortality, accounting for potential confounders. The study employed restricted cubic spline analysis to investigate the non-linear association between dietary folate levels and mortality from all causes and cardiovascular disease.

RESULTS

Our final cohort consisted of 3,266 NAFLD patients, with a median follow-up of 10.3 years, 691 deaths were observed, including 221 cardiovascular deaths. Compared to participants with a folate intake in Quartile 1 (≤250 μg/d), those in Quartile 4 (≥467.5 μg/d) had multivariable-adjusted hazard ratios of 0.69 (95% CI, 0.51-0.94) for all-cause mortality (p for trend = 0.028) and 0.55 (95% CI, 0.29-1.04) for CVD mortality (p for trend = 0.107). A non-linear relationship between dietary intake and risk of death was not observed.

CONCLUSION

Greater dietary folate intake is associated with a reduced risk of all-cause in American adults with NAFLD. Higher dietary folate intake not found to be associated with lower CVD mortality. These findings suggest that dietary folate may improve the prognosis of adult NAFLD patients. The measured-response relationship between dietary folate intake and mortality in patients with NAFLD requires further investigation.

Association of serum folate concentrations with the mortality of cancer: a prospective cohort study

BACKGROUND

The association between serum folate concentrations and the mortality of cancer remains unclear. We aim to investigate the association of serum folate concentrations with all-cause and cause-specific mortality among American adults with cancer.

METHODS

This cohort study included 4535 patients with cancer from National Health and Nutrition Examination Survey (NHANES) 1999 to 2016 and NHANES III (1988-1994). Death outcomes were ascertained by linkage to National Death Index records through 31 December 2019. Cox proportional hazards model and two-piecewise Cox proportional hazards model were used to calculate hazard ratios and 95% confidence intervals for the associations between folate concentrations and the risk of mortality.

RESULTS

During a median follow-up of 37,792 person-years, there were 1998 all-cause deaths and 616 cancer deaths. Non-linear and L-shaped associations were observed between serum folate concentrations and the risk of all-cause and cancer mortality among patients with cancer. Notably, the mortality rates reached a plateau at 23.7 ng/mL for all-cause mortality and 23.57 ng/mL for cancer mortality. When folate levels fell below these thresholds, the risk of all-cause and cancer mortality decreased by approximately 2.1% (HR 0.979; 95% CI 0.969-0.989) and 3.6% (HR 0.964; 95% CI 0.948-0.981), respectively, with each unit increase in the folate concentration up to the thresholds.

CONCLUSION

Our study reveals that low serum folate concentrations are linked to an elevated risk of cancer mortality among individuals with cancer within a certain range and supplementation of folate in cancer patients to achieve specific serum folate level threshold (23.7 ng/mL) might reduce the risk of cancer mortality.

Effects of folate deficiency and sex on carcinogenesis in a mouse model of oral cancer

OBJECTIVES

To investigate the effects of dietary folate and sex on histopathology of oral squamous cell carcinoma in mice.

MATERIALS AND METHODS

Mice (C57Bl/6, 30/sex) were fed either a deficient folate or sufficient folate diet. Vehicle or 4-nitroquinoline1-oxide (50 μg/mL) in vehicle were administered in drinking water for 20 weeks, followed by 6 weeks of regular drinking water. Oral lesions were observed weekly. Tongues were studied for histopathologic changes. Immunohistochemical techniques were used to measure cell proliferation (Ki67+), and to quantify expression of folate receptor, reduced folate carrier, and proton-coupled folate transporter. T cells, macrophages, and neutrophils were counted and normalized to area.

RESULTS

All 4NQO-treated mice developed oral tumors. Dietary folate level did not affect tumor burden. More tumors were observed on the ventral aspect of the tongue than in other locations within the oral cavity. 4-nitroquinoline-1-oxide-treated mice displayed 27%-46% significantly lower expression of all three folate transport proteins; diet and sex had no effect on folate transporter expression. T-cell and neutrophil infiltration in tongues were 9.1-fold and 18.1-fold increased in the 4-nitroquinoline-1-oxide-treated mouse tongues than in controls.

CONCLUSION

Treatment with 4NQO was the primary factor in determining cancer development, decreased folate transport expression, and lymphoid cell infiltration.

Association between Serum Folate and Vaginal High-Risk Human Papillomavirus Infections in United States Women

BACKGROUND

Serum concentration of folate was inversely associated with cervical intraepithelial neoplasia and cervical cancer in some studies. The association between folate and human papillomavirus (HPV) infection, a necessary cause of cervical cancer, has not been well elucidated.

OBJECTIVES

We evaluated whether serum folate concentrations were associated with high-risk HPV (hrHPV) infection.

METHODS

The study population was 11,801 females, aged 18-59 y, enrolled in the National Health and Nutrition Examination Survey (NHANES), from 2003 to 2016, in the United States. In this cross-sectional study, prevalence ratios (PRs) of vaginal hrHPV were calculated using logistic regression models, by quintiles of serum folate.

RESULTS

Females in the lowest quintile had <21.3 nmol/L of folate. Approximately 23% of the females (2733/11,801) were hrHPV positive. In age-adjusted models, folate was significantly associated with hrHPV infection. The PRs and 95% confidence intervals (CIs) were (PR: 1.52; 95% CI: 1.37, 1.70) for the first, (PR: 1.29; 95% CI: 1.15, 1.44) for the second, (PR: 1.19; 95% CI: 1.06, 1.34) for the third, and (PR: 1.09; 95% CI: 0.96, 1.23) for the fourth quintiles, compared with the females in the highest quintile, with a significant P value for trend, <0.0001. The association remained statistically significant after the models were further adjusted for lifestyle and sexual risk factors for hrHPV infection; the females in the lowest quintile were more likely to have hrHPV infection than those in the highest quintile (PR: 1.40; 95% CI: 1.11, 1.53).

CONCLUSIONS

Results from this sample of females in the United States suggest that serum folate concentration is inversely associated with hrHPV infection.

Association Between Nutrients and Cardiovascular Diseases

Cardiovascular diseases (CVD) constitute a leading cause of global mortality. Inflammation and oxidative stress are key molecular underpinnings of CVD pathogenesis. This comprehensive review explores the multifaceted role of nutrients in cardiovascular health beyond their impact on cardiac events. The manuscript examines the influence of macronutrients such as fats and carbohydrates, as well as micronutrients including vitamins and folate, on CVD. Additionally, the interplay between dietary supplements and CVD risk reduction is investigated. The purpose of this manuscript is to provide a comprehensive overview of the diverse mechanisms through which nutrients contribute to cardiovascular well-being, addressing both cardioprotective effects and their broader implications. Through an analysis of pertinent studies, we illuminate the complex relationship between nutrition, lifestyle, and cardiovascular health, underscoring the significance of a holistic approach to CVD prevention and management.

Associations between homocysteine, vitamin B12, and folate and the risk of all-cause mortality in American adults with stroke

Objective

Associations between plasma homocysteine (Hcy), vitamin B12, and folate and the risk of all-cause mortality are unclear. This study aimed to examine whether plasma Hcy, vitamin B12, and folate levels independently predict the risk of all-cause mortality in American adults with stroke.

Methods

Data from the United States National Health and Examination Survey (NHANES; 1999-2006) were used and linked with the latest (2019) National Death Index (NDI). Cox proportional hazards models and restricted cubic splines were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of all-cause mortality for Hcy, folate, and B12 levels in adults with stroke. Sample weights were calculated to ensure the generalizability of the results.

Results

A total of 431 participants were included (average age: 64.8 years). During a median follow-up of 10.4 years, 316 deaths occurred. Hcy was positively associated with all-cause mortality in adults with stroke (HR, 1.053; 95% CI: 1.026-1.080). Stroke patients with plasma Hcy levels in the fourth quartile had a 1.631-fold higher risk of all-cause mortality (HR, 1.631; 95% CI: 1.160-2.291) than those in the first quartile. The association between plasma Hcy and all-cause mortality was strong significant in older patients (p for interaction = 0.020). Plasma folate and vitamin B12 concentrations were inversely correlated with Hcy concentrations [B-value (95% CI): -0.032 (-0.056- -0.008), -0.004 (-0.007- -0.002), respectively]. No significant associations were observed between folate, vitamin B12 levels, and all-cause mortality in adults with stroke.

Conclusion

Plasma Hcy levels were positively associated with all-cause mortality in older adults with stroke. Folate and vitamin B12 levels were inversely correlated with Hcy. Plasma Hcy may serve as a useful predictor in mortality risk assessment and targeted intervention in adults with stroke.

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

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

Correlation of several forms of folic acid with endometrial cancer: cross-sectional data from the National Health and Nutrition Examination Surveys (NHANES) 2011-2018

OBJECTIVE

Endometrial cancer (EC) is a common malignancy of the female reproductive system and although most patients have a good prognosis, 20-30% of patients with advanced disease have a poor prognosis. There are currently no reliable biomarkers for early diagnosis and effective prognostic improvement of the disease. The purpose of this study was to explore the correlation between different forms of folic acid and endometrial cancer.

METHODS

This study included 8809 female subjects aged ≥ 20 years in the NHANES database from 2011 to 2018, including 8738 non-oncology patients and 71 EC patients. Selection bias was reduced using 1:1 propensity score matching (PSM) method. Restricted cubic spline (RCS) was plotted to explore the non-linear relationship between different forms of folic acid and EC.

RESULT

Using data from the NHANES database from 2011 to 2018, the association between folic acid and the risk of developing EC was assessed. The results of the 1:1 ratio propensity score matching (PSM) showed 68 each for EC patients and non-oncology participants. Total serum folate, 5-methyltetrahydrofolate (5-methylTHF), 5-formyltetrahydrofolate (5-formylTHF), tetrahydrofolate (THF) and 5,10-methylenetetrahydrofolate (5,10-methenylTHF) were significantly correlated with EC (p < 0.05). In addition, the RCS showed a significant non-linear correlation between THF and 5,10-formyl THF and the risk of developing EC.

CONCLUSION

The results of this study showed that changes in serum total folate, 5-methylTHF, 5-formylTHF, THF and 5,10-methenylTHF were related to EC.

Comparison of data-driven identified hypertension-protective dietary patterns among Chinese adults: based on a nationwide study

PURPOSE

Diet pattern (DP) is a key modifiable and cost-effective factor in hypertension (HTN) management. The current study aimed to identify and compare the hypertension-protective DPs among Chinese adults.

METHODS

52,648 participants aged over 18 years were included from China Nutrition and Health Surveillance (CNHS) 2015-2017. Reduced rank regression (RRR) and partial least square regression (PLS) was applied to identify the DPs. Multivariable-adjusted logistic regression was used to assess the association between the DPs and HTN.

RESULTS

DPs derived by RRR and PLS were both featured by higher consumption of fresh vegetables and fruits, mushrooms and edible fungi, seaweeds, soybeans and related products, mixed legumes, dairy products, fresh eggs, and lower of refined grain consumption. Compared to the lowest quintile, participants in the highest quintile had lower odds of HTN (RRR-DP: OR = 0.77, 95% CI = 0.72-0.83; PLS-DP: OR = 0.76, 95% CI = 0.71-0.82; all p < 0.0001). Simplified DP scores were observed the same protective tendencies (Simplified RRR-DP: OR = 0.81, 95% CI = 0.75-0.87; Simplified PLS-DP: OR = 0.79, 95% CI = 0.74-0.85; all p < 0.0001) and showed effective extrapolation in subgroups defined by gender, age, location, lifestyle, and different metabolic conditions.

CONCLUSIONS

The identified DPs had high conformity with East Asian dietary habits, and significantly negative associations with HTN among Chinese adults. The simplified DP technique also indicated the potential for improving the extrapolation of the results of DP analysis related to HTN.

Non-linear associations of serum and red blood cell folate with risk of cardiovascular and all-cause mortality in hypertensive adults

This study aims to assess the associations of serum and red blood cell (RBC) folate with cardiovascular and all-cause mortality in hypertensive adults. Data on serum and RBC folate from the 1999-2014 National Health and Nutrition Examination Survey were included. Through December 31, 2015, cardiovascular and all-cause mortality were identified from the National Death Index. Multiple Cox regression and restricted cubic spline analyses were used to determine the relationship between folate concentrations and outcomes. A total of 13,986 hypertensive adults were included in the analysis (mean age, 58.5 ± 16.1 years; 6898 [49.3%] men). At a median of 7.0 years of follow-up, 548 cardiovascular deaths and 2726 all-cause deaths were identified. After multivariable adjustment, the fourth quartile of serum folate was associated with cardiovascular (HR = 1.32 [1.02-1.70]) and all-cause (HR = 1.20 [1.07-1.35]) mortality compared to the second quartile, whereas the first quartile was only linked with increased all-cause (HR = 1.29 [1.15-1.46]) mortality. The inflection points for the non-linear associations of serum folate with cardiovascular and all-cause mortality were 12.3 ng/mL and 20.5 ng/mL, respectively. In addition, the highest quartile of RBC folate was associated with cardiovascular (HR = 1.68 [1.30-2.16]) and all-cause (HR = 1.30 [1.16-1.46]) mortality compared to the second quartile, but the lowest quartile was not associated with either outcome. The inflection points for the non-linear associations of RBC folate with cardiovascular and all-cause mortality were 819.7 and 760.1 ng/mL, respectively. The findings suggest non-linear associations between serum and RBC folate levels and the risk of cardiovascular and all-cause mortality in hypertensive adults.

Associations of Serum Folate and Homocysteine Concentrations with All-Cause, Cardiovascular Disease, and Cancer Mortality in Men and Women in Korea: the Cardiovascular Disease Association Study

BACKGROUND

Evidence on the association of serum folate and homocysteine concentrations with risk of mortality in the general population is unclear.

OBJECTIVES

This study aimed to examine the associations of serum folate and homocysteine concentrations with all-cause, CVD, and cancer mortality risk in Korean men and women aged ≥40 y.

METHODS

In this population-based prospective cohort study, serum folate and homocysteine concentrations were measured in a subset of participants enrolled between 2005 and 2012. A total of 21,260 participants were linked to mortality data from the survey date to 31 December 2019. Cox proportional hazards models and restricted cubic splines were used to identify the associations of serum folate and homocysteine concentrations with mortality.

RESULTS

During a median follow-up of 12.3 y, 2501, 549, and 842 deaths were attributed to all-cause, CVD, and cancer, respectively. The prevalence of folate deficiency and hyperhomocysteinemia were higher in men than in women. In men, a nonlinear inverse association was observed between serum folate concentrations and all-cause mortality. Men in the third quartile of serum folate concentrations exhibited a lower risk of all-cause mortality (HR: 0.85; 95% CI: 0.73, 0.99) than those in the lowest quartile. Serum homocysteine concentration was positively associated with all-cause and CVD mortality. Men and women in the highest compared with those in the lowest serum homocysteine quartile showed a higher risk of CVD mortality (HR: 1.60; 95% CI: 1.07, 2.39; and HR: 1.79; 95% CI: 1.11, 2.89, respectively). Hyperhomocysteinemia combined with folate deficiency was associated with increased all-cause, CVD, and cancer-related mortality rates.

CONCLUSIONS

Higher serum homocysteine and lower serum folate concentrations were associated with an increased risk of all-cause, CVD, and cancer-related mortality in Korean adults. The finding of a nonlinear inverse relationship between serum folate concentration and mortality in men warrants further investigation.

Association between dietary intake of one-carbon metabolism nutrients and hyperglycemia in coal-burning fluorosis areas of Guizhou, China

Background and aims

There are limited studies describing the association between dietary intake of one-carbon metabolism nutrients and hyperglycemia. The present study aimed to investigate the association of habitual dietary intake of one-carbon metabolism nutrients with hyperglycemia in a fluorosis area in China, and explored the interaction between these nutrients and fluorosis related to hyperglycemia.

Method

In a cross-sectional study, we recruited 901 villagers, ages ranging from 18–75, in Guizhou Province. Dietary data and other covariate data were obtained through an interviewer-administered questionnaire. We collected venous blood samples from participants who had fasted for one night to obtain fasting blood glucose levels and we categorized dietary intake of betaine, total choline, methionine, folate, vitamins B₆ and B₁₂, and choline subclasses into quartiles (Q1–Q4). The lowest quartile (Q1) served as the reference group. An unconditional logistic regression model was used to evaluate the protective effects of a dietary intake of one-carbon nutrients against hyperglycemia. We calculated Odds Ratios (ORs) with 95% confidence intervals (CIs). A presence or absence of fluorosis subgroup analysis was performed to determine the potential effect of fluorosis on hyperglycemia.

Result

After adjusting for potential confounding factors, we found that a greater intake of dietary vitamin B₆, total choline and methyl-donor index was inversely associated with the occurrence of hyperglycemia (P-trend <0.05). However, there were no significant associations between hyperglycemia and the dietary intake of folate, vitamin B₁₂, methionine, and betaine. As for the choline subgroups, it showed that the dietary intake of free choline, phosphatidylcholine, and glycerol phosphatidylcholine was negatively correlated with the occurrence of hyperglycemia (P < 0.05). In contrast, there was no statistical association between dietary phosphatidylcholine and sphingomyelin and hyperglycemia (all P > 0.05). The results of subgroup analysis showed that dietary intake of folate, vitamin B₆, total choline, free choline, glycerol phosphorylcholine, and phosphocholine had a protective effect against the occurrence of hyperglycemia in the non-fluorosis subgroup, although no effects were observed in the fluorosis subgroup. There were significant interactions between these nutrients and fluorosis (P = 0.010–0.048).

Conclusion

The study demonstrated that higher dietary intake of vitamin B₆, total choline, methyl-donor index, free choline, glycerol phosphorylcholine, and phosphocholine in choline compounds were associated with a lower incidence of hyperglycemia. Moreover, the associations were modified by the presence or absence of fluorosis. Further investigation is needed to test the association in large-scale follow-up studies.

Non-Linear Association between Serum Folate Concentration and Dyslipidemia: Korea National Health and Nutrition Examination Survey (KNHANES) 2016-2018

Objectives

We aimed to evaluate the association between serum folate concentration and prevalence of dyslipidemia.

Methods

A total of 4,477 adults (2,019 men and 2,458 women) enrolled in the Korea National Health and Nutrition Examination Survey (KNHANES) 2016-2018 were included. Serum samples were used to access folate concentration and total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL)-cholesterol, and high-density lipoprotein (HDL)-cholesterol levels. Multivariate logistic regression with a sampling weight was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

Results

Elevated TC, TG, LDL-cholesterol and HDL-cholesterol were observed in 506 (11.3%), 646 (14.4%), 434 (9.7%), and 767 (17.1%) participants, respectively. We found non-linear trends between serum folate concentration and prevalence of hypercholesterolemia and hyper-LDL cholesterolemia from the restricted cubic smoothing spline. A higher prevalence of hypercholesterolemia was observed among participants in the 1st tertile serum folate concentration group (OR [95% CI] = 1.38 [1.05-1.79]) compared to those in the 2nd tertile group. On the other hand, a higher prevalence of hyper-LDL cholesterolemia was identified for both the 1st and 3rd serum folate concentration tertile groups (OR [95% CI]: 1.49 [1.08-2.05] and 1.63 [1.20-2.20], respectively); furthermore, in these tertiles, the prevalence of hyper-LDL cholesterolemia was more pronounced among obese participants.

Conclusion

Non-linear associations may exist between serum folate concentration and the prevalence of hypercholesterolemia and hyper-LDL cholesterolemia in adults. The findings suggest that more accurate recommendations about folate intake and folic acid fortification and supplementation should be provided.

Serum folate deficiency and the risks of dementia and all-cause mortality: a national study of old age

BACKGROUND

The association between serum folate deficiency and the risk of dementia in old age is unclear, perhaps owing to small sample sizes, the competing risk of mortality or reverse causation.

OBJECTIVE

To examine the associations between serum folate deficiency and the risks of incident dementia and all-cause mortality in a large national sample of older adults.

METHODS

A prospective cohort aged 60-75 years (n=27 188) without pre-existing dementia for at least 10 years, was tested for serum concentrations of folate and followed up for dementia or all-cause mortality. Serum folate deficiency was classified as present (<4.4 ng/mL), otherwise absent. HRs and 95% CIs from competing risks Cox models were fitted to quantify the associations between serum folate deficiency and the risks of dementia and all-cause mortality. To examine reverse causation, the analysis was stratified by duration of follow-up.

FINDINGS

The presence compared with the absence of serum folate deficiency was associated with higher risks of dementia (HR=1.68; 95% CI 1.32 to 2.13; p<0.001) and all-cause mortality (HR=2.98; 95% CI 2.52 to 3.52; p<0.001). Evidence for reverse causation were moderate for dementia and mild for all-cause mortality.

CONCLUSIONS

Serum concentrations of folate may function as a biomarker used to identify those at risk of dementia and mortality; however, reverse causation is likely. Further research is needed to examine the role of serum folate deficiency in dementia aetiology.

CLINICAL IMPLICATIONS

Serum folate deficiency in older adults requires monitoring and treatment for preventative measures and/or as part of implemented therapeutic strategies.

Associations of Serum and Red Blood Cell Folate With All-Cause and Cardiovascular Mortality Among Hypertensive Patients With Elevated Homocysteine

Objectives

This study aims to explore the associations between serum and red blood cell (RBC) folate as indicators of short- and long-term folate status, respectively, and all-cause as well as CVD mortality among hypertensive patients with elevated homocysteine.

Methods

A prospective cohort study of the National Health and Nutrition Examination Survey (1999–2006) and 2015 Linked Mortality File was performed. All-cause and CVD mortality risk estimated using Cox proportional hazards models with adjusting for multiple potential covariates.

Results

A total of 1,753 hypertensive patients with elevated homocysteine [mean (SD) age, 68.5 (13.1)] were included in the analysis. During a median follow-up of 10.0 years, a total of 899 all-cause and 257 CVD deaths occurred. Compared the highest with the lowest quartile of RBC folate, the multivariable adjusted hazard ratios and 95% confidence intervals for all-cause and CVD death were 1.13 (0.92–1.39) and 1.47 (1.01–2.16) respectively. There was a significant and positive trend between RBC folate and the risk of CVD death (p for trend = 0.0196). No significant association was found between serum folate and mortality risk among the study sample.

Conclusions

High level of RBC folate is associated with an increased risk of cardiovascular mortality among hypertensive patients with elevated homocysteine while serum folate has no such effects.

Inverse Association of Serum Folate Level with Metabolic Syndrome and Its Components in Korean Premenopausal Women: Findings of the 2016–2018 Korean National Health Nutrition Examination Survey

Research on the association of serum folate levels with metabolic syndrome (MetS) in premenopausal women is lacking. This study was aimed to investigate this association in 1730 premenopausal women using the 2016 to 2018 Korean National Health and Nutrition Examination Survey data. Participants’ mean age and BMI were 35.9 years and 22.7 kg/m2, respectively. Participants were divided into three groups according to serum folate tertiles. Odds ratios (OR) and 95% confidence intervals (CIs) for abdominal obesity, elevated blood pressure (BP), high fasting plasma glucose (FPG), high triglycerides (TG), low high-density lipoprotein cholesterol (HDL-C), and MetS were calculated in multiple logistic regression models adjusted for possible confounders, by serum folate level tertiles. Prevalence of MetS (14.9, 11.0, and 8.6%); abdominal obesity (17.8, 16.0, and 11.4%); high TG (17.5, 14.0, and 11.1%); and low HDL-C (50.3, 44.6, and 42.5%) decreased with increasing folate level tertile. Prevalence of elevated BP (14.3, 12.0, and 11.7%) and high FPG (11.9, 15.8, and 13.0%) showed no significant differences according to serum folate level tertiles. The multivariate-adjusted ORs (95% CIs) for MetS, abdominal obesity, elevated BP, high TG, and low HDL-C in the highest folate level tertile were 2.17 (1.46–3.22), 1.80 (1.25–2.60), 1.77 (1.16–2.70), 1.90 (1.35–2.67), and 1.49 (1.14–1.94), respectively. The ORs for high FPG did not show significant differences according to serum folate level tertiles. In conclusion, serum folate levels were inversely associated with an increased risk of MetS in Korean premenopausal women. These results suggest that MetS can be prevented and managed by improving the serum folate levels in premenopausal women.

Associations of Serum Folate and Vitamin B12 Levels With Cardiovascular Disease Mortality Among Patients With Type 2 Diabetes

Importance

The associations of serum folate and vitamin B12 levels with cardiovascular outcomes among patients with type 2 diabetes (T2D) remain unclear.

Objective

To investigate the associations of serum folate and vitamin B12 levels with risk of cardiovascular disease (CVD) mortality among individuals with T2D.

Design, Setting, and Participants

This prospective cohort study included 8067 patients with T2D who participated in the National Health and Nutrition Examination Survey (NHANES) from 1999 through 2014 and NHANES III (1988-1994). American Diabetes Association criteria were used to define T2D. Data were analyzed between October 1, 2020, and April 1, 2021.

Exposures

Serum folate and vitamin B12 levels.

Main Outcomes and Measures

Multivariable Cox proportional hazards regression models were used to compute hazard ratios and 95% CIs for the associations of serum folate and vitamin B12 levels with risks of CVD and all-cause mortality. Two multivariable models were constructed. Restricted cubic spline analyses were used to examine the nonlinear association of serum folate levels and vitamin B12 levels with CVD mortality, and nonlinearity was assessed using the likelihood ratio test.

Results

This cohort study included data from 7700 participants in the folate analysis (mean [SE] age, 57.8 [0.3] years; 3882 men [weighted, 50.5%]; median serum folate level, 12.1 ng/mL [IQR, 7.1-19.5 ng/mL]) and 4860 participants for the vitamin B12 analysis (mean [SE] age, 57.8 [0.3] years; 2390 men [weighted, 50.7%]; median serum vitamin B12 level, 506.1 pg/mL [IQR, 369.1-703.5 pg/mL]). During 72 031 person-years of follow-up, 799 CVD deaths were documented for the folate analysis, and during 43 855 person-years of follow-up, 467 CVD deaths were reported for the vitamin B12 analysis. Nonlinear associations were observed for serum levels of folate (P = .04 for nonlinearity) and vitamin B12 (P = .04 for nonlinearity) with risk of CVD mortality among patients with T2D. Compared with participants in the second quartile of serum folate levels (7.1-12.1 ng/mL), the hazard ratios for CVD mortality were 1.43 (95% CI, 1.04-1.98) for participants in the lowest serum folate level quartile (<7.1 ng/mL) and 1.03 (95% CI, 0.74-1.44) for participants in the highest quartile (≥19.5 ng/mL). In addition, compared with participants in the second quartile of serum vitamin B12 levels (369.1-506.0 pg/mL), the hazard ratios for CVD mortality were 1.74 (95% CI, 1.20-2.52) for participants in the lowest quartile (<369.1 pg/mL) and 2.32 (95% CI, 1.60-3.35) for participants in the highest quartile (≥703.5 pg/mL). Similar patterns of association were observed for all-cause mortality (nonlinearity: P = .01 for folate and P = .02 for vitamin B12).

Conclusions and Relevance

This cohort study found that both low and high serum levels of vitamin B12 as well as low serum levels of folate were significantly associated with higher risk of CVD mortality among individuals with T2D.

Serum folate concentration and health-related quality of life among the elderly in South Korea

Background

The purpose of this study was to investigate the association between serum folate concentration and health-related quality of life (HRQOL) among the elderly in South Korea.

Materials and methods

The data used in this study were drawn from 1,021 participants over 65 years old in the Korea National Health and Nutrition Examination Survey from 2016–2018. HRQOL was measured by the EQ-5D questionnaire. Participants were divided into tertiles of folate concentration (ranges 1.7–5.6, 5.7–9.4, and 9.5–31.9 ng/mL). We performed multivariable linear regression to examine the relationship between folate and HRQOL, and multivariable logistic regression to examine the relationship between folate and the dimensional problem of HRQOL.

Results

Higher folate concentrations were significantly associated with higher HRQOL in the elderly. The average HRQOL score of the elderly in the highest tertile of the folate level was 0.0289 higher than that of the lowest tertile (coefficient: 0.0289; 95% CI 0.0016, 0.0563). The HRQOL score increased by 0.0174 points when the folate concentration increased by 100%. When analyzing specific dimensions, a significant association with folate concentration was found only for the self-care dimension of HRQOL (odds ratio for self-care problems: 0.63; 95% CI 0.41, 0.99).

Conclusions

The elderly with higher serum folate concentration tended to have higher HRQOL. Among HRQOL dimensions, self-care was only significantly associated with folate concentration.

Multiple vitamin co-exposure and mortality risk: A prospective study

BACKGROUND & AIMS

Existing epidemiological studies explored the associations of circulating vitamins and mortality focusing on individual vitamin effects, and controversial findings were obtained. The joint effects of multiple vitamin co-exposure are worth studying. The study aimed to elucidate the associations of circulating vitamins and the joint effects of these vitamins' co-exposure with all-cause and cause-specific mortality risks.

METHODS

We prospectively evaluated the associations of the concentrations of six kinds of vitamins (A, D, E, C, B12 and B9) in serum with risks for all-cause and cause-specific mortalities among U.S. adults. Mortality status and cause of death were determined by NHANES-linked public available files dated up to 31 December 2015. An unsupervised K-means clustering method was used to cluster the participants into several vitamin co-exposure patterns. The Cox proportional hazards model was used for statistical analysis.

RESULTS

A total of 1404 deaths occurred during a median of 10.9 years follow-up among 8295 participants. In multivariable adjustment, increasing levels of vitamin D were associated with reduced all-cause and cause-specific mortality risks. A J-shaped nonlinear exposure-response relationship was observed between all studied vitamins (except for vitamin D) and all-cause mortality risk. Four co-exposure patterns were generated based on the studied vitamins, as follows: low-level exposure (cluster 1), vitamin A/D exposure (cluster 2), water-soluble vitamin exposure (cluster 3) and high-level exposure (cluster 4). Compared with those in cluster 1, participants in cluster 2 had lower all-cause and cancer mortality risks, with hazard ratios (95% confidence intervals [CIs]) of 0.67 (0.53, 0.85) and 0.45 (0.29, 0.71), respectively.

CONCLUSIONS

The findings in this study indicated that high circulating vitamin D levels were associated with reduced mortality risk among U.S. adults. Vitamin co-exposure at moderate levels appropriately contributed to low all-cause and cancer mortality risks. Our findings provided a novel perspective for exploring the joint health effects of multivitamin co-exposure. Future investigations are needed to further unravel the underlying mechanisms of possible vitamin interactions.

Nutritional status, lifestyle habits and cancer mortality: a population-based prospective cohort study

PURPOSE

We aimed to investigate the relationship between overall nutritional status and cancer mortality.

METHODS

A total of 12 262 US adults from six consecutive surveys of the National Health and Nutrition Examination Survey (NHANES 2003-2014) were analyzed. The overall health nutritional biomarkers index (HNBI) score, capturing characteristics of 17 biomarkers was developed to assess the overall nutritional status. The lower the HNBI score, the healthier nutritional status would be. Hazard ratio (HR) and 95% confidence intervals (95% CIs) were calculated by Cox proportional hazards regression models to evaluate the association between the HNBI score and cancer mortality.

RESULTS

The lower overall HNBI score was associated with decreased risk of cancer mortality, compared with participants in the 4th quartile of overall HNBI score, the HR (95% CIs) for participants in the 1st quartiles was 0.54 (0.33-0.89) (P-trend = 0.019). Healthier lifestyle habits and not obesity interacted with HNBI score, compared with participants with higher HNBI score and smoking currently/not exercising regularly/obesity, participants with lower HNBI score and not smoking currently/exercising regularly/not obesity were associated with lower risk of cancer mortality, the HR (95% CIs) were 0.43 (0.26-0.73), 0.57 (0.33-0.97), and 0.62 (0.47-0.97), respectively. These significant associations remained among participants who were followed-up more than 2 years.

CONCLUSION

Our findings suggested that healthier overall nutritional status was associated with lower risk of cancer mortality among US adults. Not smoking, exercise regularly and not obesity interacted with overall nutritional status. Adherence to better overall nutritional status, lifestyle habits and optimal weight would prevent premature death from cancer.

Association of folate intake with cardiovascular-disease mortality and all-cause mortality among people at high risk of cardiovascular-disease

BACKGROUND & AIMS

Due to the beneficial effect of folate on cardiovascular disease (CVD), folic acid supplementation is a more common practice among people at high-risk of CVD. However, long-term prospective investigations regarding the association of folate-intake with CVD-mortality and all-cause mortality among this specific population are still lacking. Therefore, this study aims to assess the association of folate-intake with CVD-mortality and all-cause mortality.

METHODS

A total of 14,234 participants at high-risk of CVD were enrolled. Total folate equivalent (TFE), dietary folate equivalent (DFE), food folate, folic acid in fortified food, folic acid supplements, serum folate and red blood cell (RBC) folate were measured. The main outcome measures were CVD-mortality and all-cause mortality from baseline until 31 December 2015.

RESULTS

During the 98,890 person-year follow-up, 2036 deaths including 682 deaths due to CVD were documented. After multivariate adjustment, a J shaped association was found: modest intake of TFE and DFE was associated with lower risk of CVD-mortality and all-cause mortality, whereas higher intake did not persistently reduce these risks. Compared to the participants without folic acid supplementation matched 28-covariates using propensity score, folic acid supplementation was associated with higher risk of CVD-mortality (HR:1.44, 95%CI:1.06-1.97, P = 0.022) and all-cause mortality (HR:1.28,95%CI:1.09-1.51, P = 0.003). The levels of serum-folate and RBC-folate in participants with folic acid supplementation were significantly greater than participants without folic acid supplementation (41.8 nmol/l vs. 64.2 nmol/l, P < 0.001 for serum-folate; 1201 nmol/l vs. 1608 nmol/l, P < 0.001 for RBC-folate). Compared with the lowest-quintile of serum-folate, the second-quintile was consistently associated with CVD-mortality (HR:0.72, 95%CI:0.53-0.99, P = 0.048) and all-cause mortality (HR:0.78, 95%CI:0.64-0.94, P = 0.013). Compared to the lowest-quintile of RBC-folate, the second-quintile was associated with lower all-cause mortality (HR:0.71,95%CI:0.56-0.90, P = 0.005), whereas the highest-quintile was associated with higher CVD-mortality (HR:1.40,95%CI:1.02-1.93, P = 0.030). The J shaped association of serum-folate and RBC-folate with CVD-mortality and all-cause mortality was also demonstrated, further supporting the results of TFE and propensity score analysis.

CONCLUSIONS

This study suggested the beneficial effects of modest folate-intake on the improvement of long-term survival, and emphasized the potentially deleterious effects of excess folic acid supplementation among US adults at high-risk of CVD.

Personalized Nutritional Therapy Based on Blood Data Analysis for Malaise Patients

As medical doctors, we routinely check patient blood chemistry and CBC data to diagnose disease. However, these data and methods of analysis are very rarely used to find pre-disease conditions or treat undiagnosed malaise. Masatoshi Kaneko Ph.D. found that many pre-disease conditions and types of malaise could be detected using his unique method of blood data analysis, and could also be treated using personalized nutritional therapy as an alternative to using drugs. The authors of this article introduce personalized nutritional therapy based on blood data analysis (Kaneko's method), and present and discuss some clinical cases. In total, 253 pre-disease or undiagnosed patients were treated using this nutritional therapy approach, and most of them recovered from their chronic symptoms and pre-disease conditions. This novel nutritional therapy has the potential to help many presymptomatic and undiagnosed patients suffering from malaise.

The Role of Micronutrients in Ageing Asia: What Can Be Implemented with the Existing Insights

Life expectancy as a measure of population health does not reflect years of healthy life. The average life expectancy in the Asia-Pacific region has more than doubled since 1900 and is now above 70 years. In the Asia-Pacific region, the proportion of aged people in the population is expected to double between 2017 and 2050. Increased life expectancy leads to an increase in non-communicable diseases, which consequently affects quality of life. Suboptimal nutritional status is a contributing factor to the prevalence and severity of non-communicable diseases, including cardiovascular, cognitive, musculoskeletal, immune, metabolic and ophthalmological functions. We have reviewed the published literature on nutrition and healthy ageing as it applies to the Asia-Pacific region, focusing on vitamins, minerals/trace elements and omega-3 fatty acids. Optimal nutritional status needs to start before a senior age is reached and before the consequences of the disease process are irreversible. Based on the nutritional status and health issues in the senior age in the region, micronutrients of particular importance are vitamins A, D, E, C, B-12, zinc and omega-3 fatty acids. The present paper substantiates the creation of micronutrient guidelines and proposes actions to support the achievement of optimal nutritional status as contribution to healthy ageing for Asia-Pacific populations.

High Serum Folate Concentrations Are Associated with Decreased Risk of Mortality among Japanese Adults

BACKGROUND

Folate and vitamin B-12 are essential nutrients for normal cell growth and replication, but the association of serum folate and vitamin B-12 concentrations with mortality risk remains uncertain.

OBJECTIVE

This study was performed to investigate the associations of serum folate and vitamin B-12 concentrations with mortality risk and test whether the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism modifies these associations.

METHODS

A total of 3050 Japanese community residents aged ≥40 y were prospectively followed-up for mortality between 2002 and 2012. Cox proportional hazards models and restricted cubic splines were used to estimate HRs and 95% CIs of mortality.

RESULTS

During a median follow-up period of 10.2 y, 336 participants died. Higher serum folate concentrations were associated with lower risks of all-cause mortality [multivariable-adjusted HR: 0.73; 95% CI: 0.56, 0.96 for the second tertile (8.8-12.2 nmol/L; median 10.4 nmol/L) and HR: 0.61; 95% CI: 0.46, 0.80 for the third tertile (≥12.5 nmol/L; median 15.6 nmol/L) serum folate concentrations compared with the first tertile (≤8.6 nmol/L; median 7.0 nmol/L)]. This association remained significant in all sensitivity analyses. Spline analyses showed a steady decline in all-cause mortality risk with increasing serum folate concentrations up to 20-25 nmol/L. This association persisted regardless of the MTHFR C677T genotypes. For serum vitamin B-12, the multivariable-adjusted HR of 1.32 (95% CI: 0.97, 1.79) of all-cause mortality was marginally significantly greater in the first tertile compared with the second tertile. This association was attenuated and nonsignificant after the exclusion of participants with a history of cardiovascular disease or cancer, or participants aged ≥85 y at baseline, or deaths in the first 3 y of follow-up.

CONCLUSIONS

Serum folate concentrations were inversely associated with the risk of all-cause mortality in Japanese adults. Serum vitamin B-12 concentrations were not consistently associated with all-cause mortality risk after accounting for reverse-causation bias.

Serum Folate and All-Cause Mortality is of Non-Linear Relationship Among Population with Chronic Kidney Disease: A Retrospective Cohort Study

AIM

A transition toward high serum folate concentrations has been noticed following the mandatory folate fortification. To explore this further, we studied the relationship between folate and health outcomes in population with chronic kidney disease (CKD).

METHODS

We retrospectively explored the relationships between serum folate and risk of all-cause death in this population. We analyzed data of 2142 subjects with CKD who participated in the National Health and Nutrition Examination Survey (NHANES) 1999-2006. Vital status was followed through December 31, 2006.

RESULTS

Cox regression was used to estimate hazard ratios (HRs) of mortality for individuals with serum folate in rest quintiles compared with individuals with the fourth quintile. After an average follow-up of 57.4 months with 157 deaths recorded, a reversed J-shaped association was revealed after conducting multivariable adjustment. The mortality rate in population with lower and higher folate levels were 8.29% and 12.67%, respectively, and the corresponding adjusted HRs were 2.41 (95% confidence interval, CI=1.32-4.40) and 2.10 (1.20-3.70). Kaplan-Meier curve showed survival benefits for the fourth quintile of serum folate as compared to the first and fifth quintile.

CONCLUSION

Serum folate concentrations may influence all-cause mortality in a non-linear pattern in the CKD population. It is reasonable to recommend periodic surveillance in the CKD population to maintain the serum folate concentration in an appropriate level.

Serum folate modified the association between low-density lipoprotein cholesterol and carotid intima-media thickness in Chinese hypertensive adults

BACKGROUND AND AIMS

While folate is known for its importance in cardiovascular health, it is unknown whether folate status can modify the association between low-density lipoprotein cholesterol (LDL-C) and carotid intima-media thickness (CIMT). We aimed to investigate this question in a Chinese hypertensive population, who are at high-risk of low folate and atherosclerosis.

METHODS AND RESULTS

This report included 14,970 hypertensive adults (mean age 64.5 years; 40.3% male) from the China Stroke Primary Prevention Trial (CSPPT) and analyzed the fasting serum LDL-C and folate, and CIMT data obtained at the last follow-up visit. LDL-C was calculated using the Friedewald equation. Serum folate levels were measured by chemiluminescent immunoassay. CIMT was measured by ultrasound. Non-parametric smoothing plots, multivariate linear regression analysis, subgroup analyses and interaction testing were performed to examine the LDL-C-CIMI relationship and effect modification by folate. Consistent with graphic plots, multivariate linear regression showed that LDL-C levels were independently and positively associated with CIMT (β = 7.69, 95%CI: 5.76-9.62). More importantly, the relationship between LDL-C and CIMT was significantly attenuated with increasing serum folate levels (1st tertile: β = 10.06, 95%CI: 6.67-13.46; 2nd tertile: β = 6.81, 95%CI: 3.55-10.07; 3rd tertile: β = 5.96, 95%CI: 2.55-9.36; P-interaction = 0.045). Subgroup analyses showed the association between LDL-C and CIMT across serum folate tertiles was robust among various strata (all P-interaction >0.05).

CONCLUSIONS

Among Chinese hypertensive adults, the serum folate levels could modify the association between LDL-C and CIMT. Our findings, if further confirmed, have important clinical implications.

Folate content and retention in wheat grains and wheat-based foods: Effects of storage, processing, and cooking methods

Folates are essential micronutrients for human health. The aim of this study was to evaluate the effects of storage, processing and cooking methods on folate content and identify factors with great influence on folate retention in wheat grains and wheat-based foods. For this, the folate levels of wheat grains after 2-8 months of storage, wheat flours, noodles, fermented dough, steamed bun, and bread were sequentially analyzed. An average of 26% folate loss was observed after eight-month storage in wheat grains. The milling process, with an extraction rate of 70%, led to a severe (71%) folate loss. The folate retention rate in noodles was 78%. Fermentation by yeast production enabled a 1.5-4-fold enhancement of folate levels in steamed bun and bread. Boiling, steaming and baking led to a folate loss of 13%, 16%, and 11%, respectively. These results help to guide industrial/household preparation of wheat-based foods for folate nutrition.

Red blood cell folate and cardiovascular deaths among hypertensive adults, an 18-year follow-up of a national cohort

A shift towards high folate concentration has emerged following folate fortification. However, the association between folate and health outcomes beyond neural tube defects remains inconclusive. To assess the relationship between red blood cell (RBC) folate and the risk of cardiovascular death among hypertensive patients, we analyzed the data of 2,986 adults aged 19 or older with hypertension who participated in the National Health and Nutrition Examination Survey (1991-1994) as the baseline examination and were followed up through December 31, 2010. After 32,743 person-years of follow-up with an average of 11.7 (standard error = 0.03) years, 1192 deaths were recorded with 579 cardiovascular deaths. The median survival time was significantly shorter in adults in the high folate quartile than in patients in the low folate quartile: 11.97 vs. 13.85 years for heart diseases and 13.37 vs. 14.82 years for myocardial infarction deaths. The cardiovascular mortality was 13.04, 16.95, and 26.61/1,000 person-years for the groups with low, intermediate and high folate quartiles, respectively. After adjustment for age, sex and other factors, a J-shaped association emerged. The hazard ratios (HRs) of all cardiovascular deaths in patients with low, intermediate, and high folate quartiles were 1.09 (0.94, 1.27), 1.00 (reference), and 1.44 (1.31, 1.58), respectively. The corresponding HRs of acute myocardial infarction were 1.13 (0.86, 1.50), 1.00, and 2.13 (1.77, 2.57), respectively. The estimates remained significant after adjustment for BMI and medication use. Compared to moderate RBC folate levels, high folate levels were significantly associated with an increased risk of cardiovascular deaths, especially acute myocardial infarction.

Association between serum folate and cardiovascular deaths among adults with hypertension

BACKGROUND

A significant shift toward high folate concentrations has been taking place following the mandatory folate fortification. Yet the relationship between folate and health outcomes beyond neural tube defects remains understudied. We longitudinally examined relationships between serum folate and risk of cardiovascular death.

METHODS

We analyzed data of 3116 adults aged ≥19 who participated in the Third National Health and Nutrition Examination Survey, 1991-1994 and were diagnosed with hypertension. Vital status was followed through December 31, 2010. Cox regression was used to estimate hazard ratios (HRs) of cardiovascular deaths for individuals with serum folate in the first quartile and fourth quartile compared with the patients with interquartile folate.

RESULTS

After 33627 person years (p*ys) of follow-up, 1298 deaths were recorded with 638 cardiovascular disease (CVD) deaths (109 strokes and 529 heart diseases). A U-shaped association appeared after multivariable adjustment for heart disease, acute myocardial infarction, and overall CVD deaths. The mortality rate for heart disease in patients with low, moderate, and high folate were 12.18/1000 p*ys, 14.12/1000 p*ys, and 23.80/1000 p*ys, respectively, and the corresponding adjusted HRs were 1.79 (95% confidence interval, CI = 1.63-1.98), 1.00 (reference), and 1.31 (1.17-1.46). The HRs of acute myocardial infarction were 2.28 (1.80-2.88), 1.00 (reference), and 1.77 (1.42-2.20) for hypertensive patients with serum folate in low quartile, interquartile, and high quartile, respectively.

CONCLUSIONS

Among hypertensive adults, both low and high folate were associated with an elevated risk of dying from cardiovascular diseases compared with adults with moderate serum folate concentration.

Dried blood spot microbiological assay indicates high prevalence of folate deficiency in rural adult men and women in the Haitian Central Plateau

BACKGROUND

Although folate deficiency is linked to adverse health effects, limited data exist characterizing the problem in rural settings. This study determined the prevalence of folate deficiency and anemia in rural adults in the Haitian Central Plateau using combined laboratory methods.

METHODS

Dried blood spots (DBSs) and hemoglobin measurements were collected from adult men and women selected by cluster random sampling in Haiti's Central Plateau. DBSs were analyzed for folate using a microbiological assay. Hemoglobin levels were determined using both a HemoCue photometer and the sodium lauryl sulfate microplate method. Red cell folate (RCF) levels were determined by normalizing DBS folate to hemoglobin.

RESULTS

Of the 197 subjects assessed for hemoglobin, 11.4% of males and 21.0% of females were anemic (male: hemoglobin<12 g/dL; female: hemoglobin<11 g/dL). Of the 173 subjects assessed for RCF, 27.9% of men and 14.9% of women were folate deficient (RCF<340 nmol/L). Among reproductive-age women, 83.6% had RCF levels associated with a risk of neural tube defects of >14 per 10 000 live births (RCF≤699 nmol/L).

CONCLUSIONS

Adults in the Haitian Central Plateau suffer from high rates of anemia and folate deficiency, putting the population at elevated risk for disease. DBSs and microbiological assay make folate evaluation feasible, even in low-resource regions.

Circulating Folate Concentrations and Risk of Peripheral Neuropathy and Mortality: A Retrospective Cohort Study in the U.K

Background: Folate deficiency may increase the risk of peripheral neuropathy but there is a paucity of data from large prospective studies examining this association. Methods: Longitudinal analysis of electronic health records in The Health Improvement Network (THIN), a U.K. primary care database including 594,338 patients aged 18–70 years with a folate measurement and without a history of peripheral neuropathy. Results: After a mean follow-up of 3.71 (standard deviation (SD) = 3.14) years, 1949 patients were diagnosed with peripheral neuropathy and 20,679 patients died. In those <40 years, compared to patients with folate ≥13.6 nmol/L, those with folate <6.8 (deficient) and 6.8–13.5 nmol/L (insufficient) had a hazard ratio (HR) for peripheral neuropathy of 1.83 (95% confidence intervals (CI) = 1.16–2.91) and 1.48 (95% CI = 1.04–2.08), respectively. There was no significant association between folate and peripheral neuropathy among those aged 41–70 years. Compared to patients with folate ≥ 13.6 nmol/L, folate <6.8 nmol/L was associated with a greater risk of death among all ages. Conclusion: Folate deficiency and insufficiency was associated with a greater risk of peripheral neuropathy among younger patients. This investigation should be replicated in other large datasets and it may be important to monitor peripheral neuropathy incidence after the introduction of mandatory folic acid fortification of flour in the U.K.

Voluntary fortification is ineffective to maintain the vitamin B12 and folate status of older Irish adults: evidence from the Irish Longitudinal Study on Ageing (TILDA)

Mandatory fortification of staple grains with folic acid and/or vitamin B12 (B12) is under debate in many countries including Ireland, which has a liberal, but voluntary, fortification policy. Older adults can be at risk of both deficiency and high folate status, although little is known on the actual prevalence and the major predictors. Population prevalence estimates from older adults (n 5290 ≥50 years) from the Irish Longitudinal Study on Ageing (TILDA) (Wave 1) are presented here. Measures included plasma total vitamin B12 and folate, whereas predictors included detailed demographic, socio-economic, geographic, seasonal and health/lifestyle data. The prevalence of deficient or low B12 status (45 nmol/l) was observed in 8·9 %, whereas high B12 status was observed in 3·1 % (>601 pmol/l). The largest positive predictor of B12 concentration was self-reported B12 injection and/or supplement use (coefficient 51·5 pmol/; 95 % CI 9·4, 93·6; P=0·016) followed by sex and geographic location. The largest negative predictor was metformin use (-33·6; 95 % CI -51·9, -15·4; P<0·0001). The largest positive predictor of folate concentration was folic acid supplement use (6·0; 95 % CI 3·0, 9·0 nmol/l; P<0·001) followed by being female and statin medications. The largest negative predictor was geographic location (-5·7; 95 % CI -6·7, -4·6; P<0·0001) followed by seasonality and smoking. B-vitamin status in older adults is affected by health and lifestyle, medication, sampling period and geographic location. We observed a high prevalence of low B12 and folate status, indicating that the current policy of voluntary fortification is ineffective for older adults.

Circulating Micronutrient Biomarkers Are Associated With 3 Measures of Frailty: Evidence From the Irish Longitudinal Study on Ageing

OBJECTIVES

To examine the associations between 3 frailty instruments and circulating micronutrients in a large representative sample of older adults.

DESIGN

Cross-sectional data from a nationally representative cohort study conducted between October 2009 and July 2011.

PARTICIPANTS AND SETTING

Adults age ≥50 years (n = 4068) living in the community in Ireland.

MEASUREMENTS

Circulating micronutrients (lutein, zeaxanthin, folate, vitamin B-12, and vitamin D) were measured, transformed, and standardized. Frailty was assessed using the Frailty Phenotype, the Frailty Index, and the FRAIL Scale (fatigue, resistance, ambulation, illnesses, and loss of weight), instruments. Multinomial logistic regression determined associations between micronutrients and prefrailty or frailty. Models were adjusted for sociodemographic, lifestyle, health, and seasonal factors.

RESULTS

Adjusting for age, sex, and educational attainment, all 3 measures of frailty were associated with lower levels of lutein [relative risk ratios (RRRs): 0.43‒0.63], zeaxanthin (RRRs: 0.49‒0.63), and vitamin D (RRRs: 0.51‒0.75), and with the accumulation of micronutrient insufficiencies (RRRs: 1.42‒1.90). Attenuated but significant associations were also observed with all measures of prefrailty for lutein, vitamin D, and number of micronutrient insufficiencies. The associations with frailty persisted following additional adjustment for social, lifestyle, and health and seasonal factors, and following multiple test correction.

CONCLUSIONS AND IMPLICATIONS

We have presented the most consistent evidence in the largest study to date that micronutrient concentrations are associated with prefrailty and frailty in older adults. Our data suggest that low micronutrient status has potential as an easily modifiable marker and intervention target for frailty and supports further investigation into micronutrient supplementation and fortification to prevent frailty and disability among older adults.

Association of dietary folate and vitamin B-12 intake with genome-wide DNA methylation in blood: a large-scale epigenome-wide association analysis in 5841 individuals

BACKGROUND

Folate and vitamin B-12 are essential micronutrients involved in the donation of methyl groups in cellular metabolism. However, associations between intake of these nutrients and genome-wide DNA methylation levels have not been studied comprehensively in humans.

OBJECTIVE

The aim of this study was to assess whether folate and/or vitamin B-12 intake are asssociated with genome-wide changes in DNA methylation in leukocytes.

METHODS

A large-scale epigenome-wide association study of folate and vitamin B-12 intake was performed on DNA from 5841 participants from 10 cohorts using Illumina 450k arrays. Folate and vitamin B-12 intakes were calculated from food-frequency questionnaires (FFQs). Continuous and categorical (low compared with high intake) linear regression mixed models were applied per cohort, controlling for confounders. A meta-analysis was performed to identify significant differentially methylated positions (DMPs) and regions (DMRs), and a pathway analysis was performed on the DMR annotated genes.

RESULTS

The categorical model resulted in 6 DMPs, which are all negatively associated with folate intake, annotated to FAM64A, WRAP73, FRMD8, CUX1, and LCN8 genes, which have a role in cellular processes including centrosome localization, cell proliferation, and tumorigenesis. Regional analysis showed 74 folate-associated DMRs, of which 73 were negatively associated with folate intake. The most significant folate-associated DMR was a 400-base pair (bp) spanning region annotated to the LGALS3BP gene. In the categorical model, vitamin B-12 intake was associated with 29 DMRs annotated to 48 genes, of which the most significant was a 1100-bp spanning region annotated to the calcium-binding tyrosine phosphorylation-regulated gene (CABYR). Vitamin B-12 intake was not associated with DMPs.

CONCLUSIONS

We identified novel epigenetic loci that are associated with folate and vitamin B-12 intake. Interestingly, we found a negative association between folate and DNA methylation. Replication of these methylation loci is necessary in future studies.

Serum folate concentrations at diagnosis are associated with hepatocellular carcinoma survival in the Guangdong Liver Cancer Cohort study

Existing data on folate status and hepatocellular carcinoma (HCC) prognosis are scarce. We prospectively examined whether serum folate concentrations at diagnosis were associated with liver cancer-specific survival (LCSS) and overall survival (OS) among 982 patients with newly diagnosed, previously untreated HCC, who were enrolled in the Guangdong Liver Cancer Cohort (GLCC) study between September 2013 and February 2017. Serum folate concentrations were measured using chemiluminescent microparticle immunoassay. Cox proportional hazards models were performed to estimate hazard ratios (HR) and 95 % CI by sex-specific quartile of serum folate. Compared with patients in the third quartile of serum folate, patients in the lowest quartile had significantly inferior LCSS (HR = 1·48; 95 % CI 1·05, 2·09) and OS (HR = 1·43; 95 % CI 1·03, 1·99) after adjustment for non-clinical and clinical prognostic factors. The associations were not significantly modified by sex, age at diagnosis, alcohol drinking status and Barcelona Clinic Liver Cancer (BCLC) stage. However, there were statistically significant interactions on both multiplicative and additive scale between serum folate and C-reactive protein (CRP) levels or smoking status and the associations of lower serum folate with worse LCSS and OS were only evident among patients with CRP > 3·0 mg/l or current smokers. An inverse association with LCSS were also observed among patients with liver damage score ≥3. These results suggest that lower serum folate concentrations at diagnosis are independently associated with worse HCC survival, most prominently among patients with systemic inflammation and current smokers. A future trial of folate supplementation seems to be promising in HCC patients with lower folate status.

Nutritional challenges for older adults in Europe: current status and future directions

Population ageing is rapidly progressing and it is estimated that by 2050 one in every five people globally will be aged 60 years or over. Research has shown that adequate nutritional status can positively impact the ageing process, resulting in improved quality of life and the prevention of chronic disease and mortality. However, due to physiological and social changes associated with ageing, older adults may be at increased risk of nutrient deficiencies. This review aims to investigate the nutrient intake and status of older adults in Europe and to explore the potential role of fortified foods and nutritional supplements in addressing some of the nutritional challenges identified in this population group. The available literature has highlighted unfavourable intakes of total and saturated fat, sugar, salt and dietary fibre together with low intakes and suboptimal status of key micronutrients such as vitamins D, B2, B12, folate and calcium. Evidence has shown that the consumption of fortified foods and use of nutritional supplements make significant contributions to intakes and status of these micronutrients in older adults. Continued monitoring of nutrient intake and status is important in light of changing fortification practices and food consumption patterns. Future strategies to address the nutritional issues identified in older adults could include the promotion of healthy food choices together with improvements of the food supply including reformulation (fat, sugar and salt), food fortification or supplementation to support successful ageing of our populations.

Arsenic, one carbon metabolism and diabetes-related outcomes in the Strong Heart Family Study

BACKGROUND

Inorganic arsenic exposure and inter-individual differences in its metabolism have been associated with cardiometabolic risk. A more efficient arsenic metabolism profile (lower MMA%, higher DMA%) has been associated with reduced risk for arsenic-related health outcomes; however, this profile has also been associated with increased risk for diabetes-related outcomes. The mechanism behind these contrasting associations is equivocal; we hypothesized one carbon metabolism (OCM) may play a role.

METHODS

We evaluated the association between OCM-related variables (nutrient intake and genetic variants) and both arsenic metabolism biomarkers (iAs%, MMA% and DMA%) and diabetes-related outcomes (metabolic syndrome, diabetes, HOMA2-IR and waist circumference) in 935 participants free of prevalent diabetes and metabolic syndrome from the Strong Heart Family Study, a family-based prospective cohort comprised of American Indian tribal members aged 14+ years.

RESULTS

Of the 935 participants free of both diabetes and metabolic syndrome at baseline, 279 (29.8%) developed metabolic syndrome over a median of 5.3 years of follow-up and of the 1458 participants free of diabetes at baseline, 167 (11.3%) developed diabetes over follow-up. OCM nutrients were not associated with arsenic metabolism, however, higher vitamin B₆ was associated with diabetes-related outcomes (higher HOMA2-IR and increased risk for diabetes and metabolic syndrome). A polymorphism in an OCM-related gene, methionine synthase (MTR), was associated with both higher MMA% (β = 2.57, 95% CI: 0.22, 4.92) and lower HOMA2-IR (GMR = 0.79, 95% CI = 0.66, 0.93 per 5 years of follow-up). Adjustment for OCM variables did not affect previously reported associations between arsenic metabolism and diabetes-related outcomes; however, the association between the MTR variant and diabetes-related outcomes were attenuated after adjustment for arsenic metabolism.

CONCLUSIONS

Our findings suggest MMA% may be a partial mediator in the association between OCM and diabetes-related outcomes. Additional mediation analyses with longer follow-up period are needed to confirm this finding. Further research is needed to determine whether excess B vitamin intake is associated with increased risk for diabetes-related outcomes.

Folic acid modulates VPO1 DNA methylation levels and alleviates oxidative stress-induced apoptosis in vivo and in vitro

Endothelial cell injury and apoptosis play a primary role in the pathogenesis of atherosclerosis. Moreover, accumulating evidence indicates that oxidative injury is an important risk factor for endothelial cell damage. In addition, low folate levels are considered a contributing factor to promotion of vascular disease because of the deregulation of DNA methylation. We aimed to investigate the effects of folic acid on injuries induced by oxidative stress that occur via an epigenetic gene silencing mechanism in ApoE knockout mice fed a high-fat diet and in human umbilical vein endothelial cells treated with oxidized low-density lipoprotein (ox-LDL). We assessed how folic acid influenced the levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG, an oxidative DNA damage marker) and cellular apoptosis in in vivo and in vitro models. Furthermore, we analyzed DNA methyltransferase (DNMT) activity, vascular peroxidase 1 (VPO1) expression, and promoter methylation in human umbilical vein endothelial cells. Our data showed that folic acid reduced 8-OHdG levels and decreased apoptosis in the aortic tissue of ApoE^−/− mice. Likewise, our in vitro experiments showed that folic acid protects against endothelial dysfunction induced by ox-LDL by reducing reactive oxygen species (ROS)-derived oxidative injuries, 8-OHdG content, and the apoptosis ratio. Importantly, this effect was indirectly caused by increased DNMT activity and altered DNA methylation at VPO1 promoters, as well as changes in the abundance of VPO1 expression. Collectively, we conclude that folic acid supplementation may prevent oxidative stress-induced apoptosis and suppresses ROS levels through downregulating VPO1 as a consequence of changes in DNA methylation, which may contribute to beneficial effects on endothelial function.

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Folic acid reduces oxidative stress-induced injuries in atherosclerosis.

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Folic acid decreases 8-OHdG levels and apoptosis in vivo and in vitro.

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Folic acid supplementation increases DNMT levels and regulates VPO1 expression.

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VPO1 expression is modulated by epigenetic silencing via promoter methylation.

Effect of Smoking and Folate Levels on the Efficacy of Folic Acid Therapy in Prevention of Stroke in Hypertensive Men

BACKGROUND AND PURPOSE

We aimed to examine whether the efficacy of folic acid therapy in the primary prevention of stroke is jointly affected by smoking status and baseline folate levels in a male population in a post hoc analysis of the CSPPT (China Stroke Primary Prevention Trial).

METHODS

Eligible participants of the CSPPT were randomly assigned to a double-blind daily treatment of a combined enalapril 10-mg and folic acid 0.8-mg tablet or an enalapril 10-mg tablet alone. In total, 8384 male participants of the CSPPT were included in the current analyses. The primary outcome was first stroke.

RESULTS

The median treatment duration was 4.5 years. In the enalapril-alone group, the first stroke risk varied by baseline folate levels and smoking status (never versus ever). Specifically, there was an inverse association between folate levels and first stroke in never smokers (P for linear trend=0.043). However, no such association was found in ever smokers. A test for interaction between baseline folate levels and smoking status on first stroke was significant (P=0.045). In the total sample, folic acid therapy significantly reduced the risk of first stroke in never smokers with folate deficiency (hazard risk, 0.36; 95% confidence interval, 0.16-0.83) and in ever smokers with normal folate levels (hazard risk, 0.69; 95% confidence interval, 0.48-0.99).

CONCLUSIONS

Baseline folate levels and smoking status can interactively affect the risk of first stroke. Our data suggest that compared with never smokers, ever smokers may require a higher dosage of folic acid to achieve a greater beneficial effect on stroke. Our findings need to be confirmed by future randomized trials.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00794885.

The Effects of Folate Supplementation on Diabetes Biomarkers Among Patients with Metabolic Diseases: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Although several studies have evaluated the effect of folate supplementation on diabetes biomarkers among patients with metabolic diseases, findings are inconsistent. This review of randomized controlled trials (RCTs) was performed to summarize the evidence on the effects of folate supplementation on diabetes biomarkers among patients with metabolic diseases. Randomized-controlled trials (RCTs) published in PubMed, EMBASE, Web of Science and Cochrane Library databases up to 1 September 2017 were searched. Two review authors independently assessed study eligibility, extracted data, and evaluated risk of bias of included studies. Heterogeneity was measured with a Q-test and with I2 statistics. Data were pooled by using the fix or random-effect model based on the heterogeneity test results and expressed as standardized mean difference (SMD) with 95% confidence interval (CI). A total of sixteen randomized controlled trials involving 763 participants were included in the final analysis. The current meta-analysis showed folate supplementation among patients with metabolic diseases significantly decreased insulin (SMD -1.28; 95% CI, -1.99, -0.56) and homeostasis model assessment of insulin resistance (HOMA-IR) (SMD -1.28; 95% CI, -1.99, -0.56). However, folate supplementation did not affect fasting plasma glucose (FPG) (SMD -0.30; 95% CI, -0.63, 0.02) and hemoglobin A1C (HbA1c) (SMD -0.29; 95% CI, -0.61, 0.03). The results of this meta-analysis study demonstrated that folate supplementation may result in significant decreases in insulin levels and HOMA-IR score, but does not affect FPG and HbA1c levels among patients with metabolic diseases.