Folic acid supplementation and blood pressure: a GRADE-assessed systematic review and dose-response meta-analysis of 41,633 participants

Effect of vitamin B2, vitamin C, vitamin D, vitamin E and folic acid in adults with essential hypertension: a systematic review and network meta-analysis

OBJECTIVES

The objective of the current study is to compare the treatment effects of different vitamins on essential hypertension to provide an initial basis for developing evidence-based practices.

DESIGN

Systematic review and network meta-analysis.

DATA SOURCES

Five electronic databases (PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov) were searched from their inception to 25 September 2023.

OUTCOMES

The primary outcomes were the difference between the intervention group and the control group in changes in office systolic blood pressure (SBP) and office diastolic blood pressure (DBP) from baseline. The secondary outcomes were the difference between the intervention group and the control group in changes in 24-hour mean ambulatory systolic blood pressure (24 hours SBP), 24-hour mean ambulatory diastolic blood pressure (24 hours DBP) and heart rate (HR) from baseline.

RESULTS

A total of 23 studies comparing five vitamins (vitamin B2, vitamin C, vitamin D, vitamin E, folic acid) and involving 2218 participants were included. The included trials were all vitamin versus placebo, so the network was star-shaped. Among the five vitamins, only vitamin E was significantly more effective at reducing SBP (mean difference: -14.14 mm Hg, 95% credible intervals: -27.62 to -0.88) than placebo. In addition, no evidence was found that any of the five vitamins influenced DBP, 24 hours SBP, 24 hours DBP, or HR. The dose of vitamins, geographical region and percentage of males (only SBP) might be sources of heterogeneity. Sensitivity and subgroup analysis revealed that the effect of vitamin intervention on blood pressure varies according to different doses of vitamins.

CONCLUSIONS

According to the results, vitamin E might be an effective measure to reduce SBP, but more research is needed to validate this finding.

PROSPERO REGISTRATION NUMBER

CRD42022352332.

Evidence on the use of alternative substances and therapies in hypertension

OBJECTIVE

Review of some of the best-known biological and non-biological complementary/alternative therapies/medicines (CAM) and their relationship with blood pressure (BP) and hypertension (HT).

SEARCH STRATEGY

Narrative review assessing a recent series of systematic reviews, meta-analyses, and clinical trials published in recent years, focusing on the effects of CAM on BP and HT.

SELECTION OF STUDIES

We searched EMBASE, MEDLINE, Cochrane Library and Google Scholar, obtaining a total of 4336 articles, finally limiting the search to 181 after applying filters.

SYNTHESIS OF RESULTS

Some studies on biological therapies show some usefulness in BP reduction with an adequate benefit-risk balance, although there is a scarcity of high-quality trials that support these results. Some mind-body therapies have shown hypothetical benefit; in contrast, others lack robust evidence.

CONCLUSIONS

Although some therapies present a reasonable risk-benefit ratio, they should in no case replace pharmacological treatment when indicated.

Metabolomic biomarkers of habitual B vitamin intakes unveil novel differentially methylated positions in the human epigenome

BACKGROUND

B vitamins such as folate (B9), B6, and B12 are key in one carbon metabolism, which generates methyl donors for DNA methylation. Several studies have linked differential methylation to self-reported intakes of folate and B12, but these estimates can be imprecise, while metabolomic biomarkers can offer an objective assessment of dietary intakes. We explored blood metabolomic biomarkers of folate and vitamins B6 and B12, to carry out epigenome-wide analyses across up to three European cohorts. Associations between self-reported habitual daily B vitamin intakes and 756 metabolites (Metabolon Inc.) were assessed in serum samples from 1064 UK participants from the TwinsUK cohort. The identified B vitamin metabolomic biomarkers were then used in epigenome-wide association tests with fasting blood DNA methylation levels at 430,768 sites from the Infinium HumanMethylation450 BeadChip in blood samples from 2182 European participants from the TwinsUK and KORA cohorts. Candidate signals were explored for metabolite associations with gene expression levels in a subset of the TwinsUK sample (n = 297). Metabolomic biomarker epigenetic associations were also compared with epigenetic associations of self-reported habitual B vitamin intakes in samples from 2294 European participants.

RESULTS

Eighteen metabolites were associated with B vitamin intakes after correction for multiple testing (Bonferroni-adj. p < 0.05), of which 7 metabolites were available in both cohorts and tested for epigenome-wide association. Three metabolites - pipecolate (metabolomic biomarker of B6 and folate intakes), pyridoxate (marker of B6 and folate) and docosahexaenoate (DHA, marker of B6) - were associated with 10, 3 and 1 differentially methylated positions (DMPs), respectively. The strongest association was observed between DHA and DMP cg03440556 in the SCD gene (effect = 0.093 ± 0.016, p = 4.07E-09). Pyridoxate, a catabolic product of vitamin B6, was inversely associated with CpG methylation near the SLC1A5 gene promoter region (cg02711608 and cg22304262) and with SLC7A11 (cg06690548), but not with corresponding changes in gene expression levels. The self-reported intake of folate and vitamin B6 had consistent but non-significant associations with the epigenetic signals.

CONCLUSION

Metabolomic biomarkers are a valuable approach to investigate the effects of dietary B vitamin intake on the human epigenome.

Folate, vitamin B6, and vitamin B12 intakes are negatively associated with the prevalence of hypertension: A national population-based study

We hypothesized that the prevalence of hypertension is related to B-vitamin intake in the general population, but it has not been sufficiently studied. This study aimed to investigate the intakes of dietary folate, vitamin B₆, and vitamin B₁₂ concerning hypertension in US adults. A total of 55 569 adults from National Health and Nutrition Examination Survey III and 1999-2014 were included in this study. Nutrient intake was collected from subjects through one or two 24-hour dietary reviews. Multiple logistic regression models were used to examine the relationship between these nutrient intakes and hypertension. Among male participants, dietary folate, vitamin B₆, and vitamin B₁₂ intakes were significantly and negatively associated with the prevalence of hypertension, with multivariate-adjusted odds ratios (ORs) of 0.61 (95% confidence interval [CI], 0.55-0.68), 0.65 (95% CI, 0.59-0.72), and 0.84 (95% CI, 0.75-0.95) for the highest quartile group compared with the lowest group. Results were similar for female participants, with multivariate-adjusted ORs of 0.63 (95% CI, 0.57-0.71), 0.60 (95% CI, 0.53-0.66), and 0.87 (95% CI, 0.77-0.98) for the highest quartile group. Moreover, there was a linear trend (P_trend < .001) in both men and women that the prevalence of hypertension tended to decrease with increased intake of folate, vitamin B₆, and vitamin B₁₂; however, the decreases above the third quartile were negligible. Dietary folate, vitamin B₆, and vitamin B₁₂ were significantly associated negatively with hypertension, indicating that these nutrients might have a protective effect against hypertension in United States adults.

The effects of folic acid supplementation on endothelial function in adults: a systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND

Endothelial dysfunction serves as an early marker for the risk of cardiovascular disease (CVD); therefore, it is an attractive site of therapeutic interventions to reduce the risk of CVD. This study was conducted to investigate the effect of folic acid supplementation on endothelial function markers in randomized controlled trials (RCTs).

METHODS

PubMed, ISI web of science, and Scopus databases were searched up to July 2022 for detecting eligible studies. A random-effects model was used for meta-analysis, and linear Meta-regression and non-linear dose-response analysis were performed to assess whether the effect of folic acid supplementation was affected by the dose and duration of intervention. Cochrane tools were also used to assess the risk of bias in the included studies.

RESULTS

Twenty-one studies, including 2025 participants (1010 cases and 1015 controls), were included in the present meta-analysis. Folic acid supplementation significantly affected the percentage of flow-mediated dilation (FMD%) (WMD: 2.59%; 95% CI: 1.51, 3.67; P < 0.001) and flow-mediated dilation (FMD) (WMD: 24.38 μm; 95% CI: 3.08, 45.68; P = 0.025), but not end-diastolic diameter (EDD) (WMD: 0.21 mm; 95% CI: - 0.09, 0.52; P = 0.176), and intercellular adhesion molecule (ICAM) (WMD: 0.18 ng/ml; 95% CI: - 10.02, 13.81; P = 0.755).

CONCLUSIONS

These findings suggest that folic acid supplementation may improve endothelial function by increasing FMD and FMD% levels.

TRIAL REGISTRATION

PROSPERO registration cod: CRD42021289744.

Folic acid protects against tuberculosis-drug-induced liver injury in rats and its potential mechanism by metabolomics

Observational study indicated that folic acid (FA) supplementation may protect against tuberculosis-drug-induced liver injury (TBLI). The aim is to investigate the effect and mechanism of FA on TBLI in rats. Liver injury was induced by a daily gavage of isoniazid (INH) and rifampicin (RIF) in the model and FA groups. Rats in the FA group were also treated with 2.5 mg/kg body weight FA. Rats in the control group were not treated. Eight rats were used in each group. The severity of liver injury was measured by the serum levels of hepatic enzymes and histological score. The metabolites in serum and liver tissues were analyzed by HPLC-Q-TOF-MS/MS. FA treatment significantly reduced alanine aminotransferase and liver necrosis. Seventy-nine differential metabolites in the serum and liver tissues were identified among the three groups. N-acylethanolamines, INH and RIF metabolites, phosphatidylcholines, lysophosphatidylcholines, monoglycerides, diglycerides and bile acids were regulated by FA treatment, involving key metabolic pathways, such as N-acylethanolamine metabolism, INH and RIF metabolism, liver regeneration, inflammation alleviation and bile acid metabolism. RT-PCR and western blotting results confirmed the altered N-acylethanolamine metabolism and improved drug metabolism by FA. In conclusion, FA was protective against TBLI, which may be related to the regulation of N-acylethanolamine metabolism and drug detoxification by FA.

The effects of green tea supplementation on cardiovascular risk factors: A systematic review and meta-analysis

Purpose

A bulk of observational studies have revealed the protective role of green tea supplementation in cardiovascular diseases. The current systematic review and meta-analysis study aimed to establish the effects of green tea supplementation on cardiovascular risk factors including lipid profile, blood pressure, glycemic control markers and CRP.

Methods

A systematic literature search of randomized clinical trials (RCTs) that investigated the effects of green tea supplementation and cardiovascular risk factors was undertaken in online databases including PubMed/Medline, Scopus, Web of Science, and Embase using a combination of green tea and cardiovascular risk factors search terms. Meta-analyses were carried out using a random-effects model. The I2 index was used to assess the heterogeneity of RCTs.

Results

Among the initial 11,286 studies that were identified from electronic databases search, 55 eligible RCTs with 63 effect sizes were eligible. Results from the random effects meta-analysis showed that GTE supplementation significantly reduced TC (WMD = -7.62; 95% CI: -10.51, -4.73; P = < 0.001), LDL-C (WMD = -5.80; 95% CI: -8.30, -3.30; P = < 0.001), FBS (WMD = -1.67; 95% CI: -2.58, -0.75; P = < 0.001), HbA1c (WMD = -0.15; 95% CI: -0.26, -0.04; P = 0.008), DBP (WMD = -0.87; 95% CI: -1.45, -0.29; P = 0.003), while increasing HDL-C (WMD = 1.85; 95% CI: 0.87, 2.84; P = 0.010). Subgroup analyses based on the duration of supplementation (≥ 12 vs. < 12 weeks), dose of green tea extract (GTE) (≥1,000 vs. < 1,000 mg/d), sex (male, female, and both), baseline serum levels of lipid profile, and glycemic control factors demonstrated different results for some risk factors.

Conclusion

The current study suggests improvements in the lipid and glycemic profiles following green tea supplementation. These findings support previous evidence showing the health benefits of green tea supplementation on cardiometabolic risk factors.

Olympic Cycle Comparison of the Nutritional and Cardiovascular Health Status of an Elite-Level Female Swimmer: Case Study Report from Slovenia

Monitoring the many aspects that are crucial to an athlete’s performance progress is vital for further training planning and for the development of performance and the sport. We evaluated a four-year change (2018 vs. 2022) in the current nutritional and cardiovascular health status of the most successful elite-level female swimmer in Slovenia. Body composition and dietary intake were assessed using dual-energy X-ray absorptiometry and a standardized food questionnaire. The concentration of blood lipids, blood pressure, and serum micronutrients (B₁₂, 25(OH)D), potassium, calcium, phosphorus, magnesium, and iron) were measured. The four-year comparison showed an improved body composition status (i.e., increased body mass and decreased body fat (percentage and mass), increased lean soft tissue and total bone mineral density (BMD) (i.e., significantly decreased BMD of a left femoral neck and increased BMD of a spine and head)). We also measured an improvement in the cardiovascular health status of some markers (i.e., decreased total cholesterol, triglycerides, and blood pressure but increased low-density lipoprotein cholesterol), most likely due to the differences in assessed dietary intake (i.e., lower carbohydrate intake, higher total and saturated fat intake, and lower sodium intake). Notably, nutrient intakes that are generally of concern (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), vitamin B₁₂ and D, calcium, iron, and zinc (except for fiber intake)) were all within recommended ranges. However, the athlete’s vitamin K and potassium intake were not adequate. Furthermore, in 2018, the athlete did not consume dietary supplements, while she now regularly uses several dietary supplements, including EPA and DHA omega-3, vitamin D, multivitamins, carbohydrate powder, and sports drink. Moreover, from the micronutrient serum, only iron levels deviated from the reference values (37 μmol/L vs. 10.7–28.6 μmol/L). The presented screening example using valid, sensitive, and affordable methods and with rapid organizational implementation may be a viable format for regular monitoring.