Lowered risks of hypertension and cerebrovascular disease after vitamin/mineral supplementation: the Linxian Nutrition Intervention Trial

The Role of Oxidative Stress in Hypertension: The Insight into Antihypertensive Properties of Vitamins A, C and E

Hypertension stands as a pervasive global health challenge, contributing significantly to mortality rates worldwide. Various factors, including lifestyle choices and dietary habits, contribute to the development of hypertension. In recent years, oxidative stress has garnered significant attention as a factor influencing hypertension risk, prompting a shift in research focus towards exploring it as a potential target for prevention and treatment. Antioxidants found in our diet, such as vitamins C, E and carotenoids exhibit the ability to neutralize reactive oxygen species, thereby mitigating oxidative stress. In addition, Vitamin A has an antioxidant effect despite not being an antioxidant itself. Consequently, supplementation or increased intake of these antioxidants has been hypothesized to potentially lower blood pressure levels and aid in the management of hypertension, thereby potentially prolonging life expectancy. Research findings regarding this effect have been diverse. This paper examines the existing literature demonstrating favorable outcomes associated with antioxidant supplementation.

Folic acid supplementation for stroke prevention: A systematic review and meta-analysis of 21 randomized clinical trials worldwide

BACKGROUND & AIMS

The AHA/ASA guidelines for primary stroke prevention are almost a decade old. The current recommendation regarding folic acid supplementation is based on only 8 clinical trials, and an additional 13 folate trials have been published since then. This meta-analysis aims to fill in critical evidence gaps by comprehensively evaluating 21 published trials with particular attention given to identifying the true influences through stratification.

METHODS

PubMed, the Cochrane Central Register of Controlled Trials, and Embase were searched from inception to April 4, 2023. This study included all randomized controlled trials (RCTs) of folic acid with stroke as one of the reporting endpoints. Relative risks and 95% confidence intervals were used to assess the association between folic acid supplementation and the risk of stroke in a random-effects model.

RESULTS

Results from the 21 pooled RCTs totaling 115,559 participants showed that folic acid supplementation significantly reduced the risk of stroke by 10% (RR 0.90, 95%CI 0.83 to 0.98). Subgroup analyses showed that folic acid efficacy was greater in areas without fortified grain or with partially-fortified grain (RR = 0.83, 95% CI 0.75 to 0.93; RR = 1.04 in areas with grain fortification, P-interaction = 0.003). In this group, folic acid supplementation was most efficacious in those without a history of stroke or myocardial infarction (RR = 0.77, 95% CI 0.68 to 0.86; RR = 0.94 for participants with a history of stroke or myocardial infarction, P-interaction = 0.008). The efficacy of folic acid remained consistent regardless of baseline folate levels, folic acid dosage, baseline vitamin B12 levels, vitamin B12 dosage, homocysteine reduction, intervention duration, and whether folic acid was taken alone or in combination (all P-interaction>0.05). All 21 trials were free of attrition bias and reporting bias, and there was no significant publication bias.

CONCLUSIONS

This is by far the largest meta-analysis of RCTs regarding folic acid supplementation and stroke, demonstrating the overall benefit of folic acid for stroke prevention. Grain fortification and history of stroke or myocardial infarction may be the most important influences on the efficacy of folic acid for stroke prevention.

Dosage exploration of combined B-vitamin supplementation in stroke prevention: a meta-analysis and systematic review

BACKGROUND

The optimal dosage range for B-vitamin supplementation for stroke prevention has not received sufficient attention.

OBJECTIVE

Our aim was to determine the optimal dosage range of a combination of folic acid, vitamin B12, and vitamin B6 supplementation in stroke prevention.

METHODS

We searched PubMed, the Cochrane Central Register of Controlled Trials, and Embase database for randomized controlled trials published between January 1966 and April 2023, whose participants received B-vitamin supplementation and that reported the number of stroke cases. Relative risk (RR) was used to measure the effect of combined supplementation on risk of stroke using a fixed-effects model. Risk of bias was assessed with the Cochrane risk-of-bias algorithm.

RESULTS

The search identified 14 randomized controlled trials of folic acid combined with vitamin B12 and vitamin B6 supplementation for stroke prevention that included 76,664 participants with 2720 stroke cases. In areas without and with partial folic acid fortification, combined B-vitamin supplementation significantly reduced the risk of stroke by 34% [RR: 0.66; 95% confidence interval (CI): 0.50, 0.86] and 11% (RR: 0.89; 95% CI: 0.79, 1.00), respectively. Further analysis showed that a dosage of folic acid ≤0.8 mg/d and vitamin B12 ≤0.4 mg/d was best for stroke prevention (RR: 0.65; 95% CI: 0.48, 0.86) in these areas. In contrast, no benefit of combined supplementation was found in fortified areas (RR: 1.04; 95% CI: 0.94, 1.16).

CONCLUSIONS

Our meta-analysis found that the folic acid combined with vitamin B12 and vitamin B6 supplementation strategy significantly reduced the risk of stroke in areas without and with partial folic acid fortification. Combined dosages not exceeding 0.8 mg/d for folic acid and 0.4 mg/d for vitamin B12 supplementation may be more effective for populations within these areas. This trial was registered at PROSPERO asCRD42022355077.

Lifestyle management of hypertension: International Society of Hypertension position paper endorsed by the World Hypertension League and European Society of Hypertension

Hypertension, defined as persistently elevated systolic blood pressure (SBP) >140 mmHg and/or diastolic blood pressure (DBP) at least 90 mmHg (International Society of Hypertension guidelines), affects over 1.5 billion people worldwide. Hypertension is associated with increased risk of cardiovascular disease (CVD) events (e.g. coronary heart disease, heart failure and stroke) and death. An international panel of experts convened by the International Society of Hypertension College of Experts compiled lifestyle management recommendations as first-line strategy to prevent and control hypertension in adulthood. We also recommend that lifestyle changes be continued even when blood pressure-lowering medications are prescribed. Specific recommendations based on literature evidence are summarized with advice to start these measures early in life, including maintaining a healthy body weight, increased levels of different types of physical activity, healthy eating and drinking, avoidance and cessation of smoking and alcohol use, management of stress and sleep levels. We also discuss the relevance of specific approaches including consumption of sodium, potassium, sugar, fibre, coffee, tea, intermittent fasting as well as integrated strategies to implement these recommendations using, for example, behaviour change-related technologies and digital tools.

Vitamin C supplementation showed greater effects on systolic blood pressure in hypertensive and diabetic patients: an updated systematic review and meta-analysis of randomised clinical trials

Results from randomised controlled trials (RCTs) testing the effect of vitamin C supplementation on blood pressure (BP) have been inconsistent. This systematic review evaluated the effects of vitamin C supplementation on BP and included RCTs testing the effects of vitamin C supplementation alone, on systolic and diastolic BP in adult participants (≥18 years). Random-effect models were conducted to estimate the pooled effects of vitamin C supplementation on BP. A total of 20 studies with 890 participants were included. The median dose of vitamin C was 757.5 mg/d, the median duration was 6 weeks. Vitamin C supplementation was found to reduce systolic BP by -3.0 mmHg (95%CI: -4.7, -1.3 mmHg; p = 0.001). Subgroup analysis showed a more pronounced effect on systolic BP in patients with hypertension (-3.2 mmHg, 95%CI -5.2, -1.2 mmHg, p = 0.002) and diabetes (-4.6 mmHg, 95%CI -8.9, -0.3 mmHg, p = 0.03). Further research needs to evaluate the long-term effect of vitamin C on BP in populations with impaired cardio-metabolic health.

Association between oxidative balance score and new-onset hypertension in adults: A community-based prospective cohort study

Introduction

Oxidative stress plays a key role in the pathophysiology of hypertension development. The oxidative balance score (OBS) comprises dietary and lifestyle pro- and anti-oxidant components and reflects the overall oxidative stress burden. We aimed to evaluate the association between the OBS and new-onset hypertension (HTN) using large, community-based, prospective Korean cohort data.

Methods

Among 10,030 participants aged 40-69 years included in the Korean Genome and Epidemiology Study, the data of 5,181 participants were analyzed. The hazard ratio (HR) and 95% confidence interval (CI) for new-onset HTN according to sex-specific OBS quartile groups were calculated using univariable and multivariable Cox proportional hazard regression analyses.

Results

During the mean 13.6-year follow-up period, 1,157 men and 1,196 women developed new-onset HTN. Compared to the Q1 group, the adjusted HRs (95%CI) for new-onset HTN in the Q2, Q3, and Q4 groups were 0.96 (0.82-1.16), 0.85 (0.72-0.99), and 0.71 (0.59-0.86) in men and 0.81 (0.69-0.95), 0.81(0.68-0.95), and 0.70 (0.57-0.84) in women, respectively.

Discussion

Individuals with high OBS are at lower risk of developing HTN. This study suggests that a healthy lifestyle and antioxidant rich diet could be a preventive strategy for HTN.

The role of B vitamins in stroke prevention

Elevated plasma levels of homocysteine (Hcy) are a recognized risk factor for stroke. This relationship represents one aspect of the debated `Hcy hypothesis'. Elevated Hcy may be an independent and treatable cause of atherosclerosis and thrombotic vascular diseases. Further observations indicate that proper dietary supplementation with B-vitamins decreases total plasma Hcy concentrations and may be an effective intervention for stroke prevention. Metabolic vitamin B₁₂ deficiency is a nutritional determinant of total Hcy and stroke risk. Genetic factors may link B vitamins with stroke severity due to the impact on Hcy metabolism of polymorphism in the genes coding for methylenetetrahydrofolate reductase, methionine-synthase, methionine synthase reductase, and cystathionine β-synthase. Several meta-analyses of large randomized controlled trials exist. However, they are not completely in agreement about B vitamins' role, particularly folic acid levels, vitamin B₁₂, and B₆, in lowering the homocysteine concentrations in people at high stroke risk. A very complex relationship exists between Hcy and B vitamins, and several factors appear to modify the preventive effects of B vitamins in stroke. This review highlights the regulating factors of the active role of B vitamins active in stroke prevention. Also, inputs for further large, well-designed studies, for specific, particularly sensitive subgroups are given.

Oral leukoplakia and the long-term risk of upper gastrointestinal cancer deaths in the Linxian dysplasia population

BACKGROUND

To investigate oral leukoplakia (OL) and risk of upper gastrointestinal (UGI) cancer deaths in the Linxian Dysplasia Nutrition Intervention Trial (NIT) cohort.

METHODS

A total of 3318 subjects with esophageal squamous dysplasia enrolled on 1 May 1985, and were followed up until 30 September 2015. Participants with OL at baseline were treated as an exposed group, while the remainder was selected as a control group. All subjects were followed monthly and reviewed quarterly by the Linxian Cancer Registry. Cox proportional hazard model was used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs).

RESULTS

During the 30-year follow-up, a total of 902 UGI cancer deaths occurred, including 541 esophageal squamous cell carcinoma (ESCC) related, 284 gastric cardia carcinoma (GCC) related, and 77 gastric noncardia carcinoma (GNCC) related deaths. Relative to subjects without OL, the long-term risk of ESCC mortality in participants with OL increased by 26.1% (HR = 1.26, 95% CI: 1.05-1.52). In the subgroup analyses, adverse effects of OL on ESCC mortality were observed especially in younger subjects (HR = 1.48, 95% CI: 1.11-1.97), females (HR = 1.44, 95% CI: 1.11-1.89), non-smokers (HR = 1.44, 95% CI: 1.15-1.81), nondrinkers (HR = 1.28, 95% CI: 1.04-1.57), and individuals with a family history of cancer (HR = 1.37, 95% CI: 1.05-1.79). No associations were observed between OL and risk of GCC and GNCC mortality.

CONCLUSIONS

OL may increase the long-term risk of ESCC mortality, especially in younger subjects, females, nondrinkers, non-smokers, and subjects with a family cancer history. Future studies are needed to explore the potentially etiological mechanism.

Value of plasma homocysteine to predict stroke, cardiovascular diseases, and new-onset hypertension: A retrospective cohort study

The influences of hyperhomocysteinemia on cardiovascular diseases (CVDs), stroke and new-onset hypertension are unclear. The aim of the study is to explore the associations of homocysteine levels with stroke, CVDs, and new-onset hypertension in Chinese individuals.This retrospective cohort study included outpatients and inpatients from the Department of Geriatrics at Ruijin Hospital affiliated to Shanghai Jiaotong University School of Medicine from January to December 2000. They were divided based on their homocysteine (Hcy) levels in 2000: Q1 (<10 μmol/L), Q2 (10-15 μmol/L), and Q3 (>15 μmol/L) and according to whether they had hypertension at baseline. Information about stroke, mortality and major adverse cardiac events, and newly onset hypertension was gathered in December each year until 2017. The effects of Hcy levels on the risk for stroke and CVDs among all patients, and new-onset hypertension among patients without hypertension at baseline were evaluated.After adjustment for confounders, compared with the Q1 group (Hcy <10 μmol/L), when the Hcy increased to 10 to 15 μmol/L, the risks for stroke, CVDs, and new-onset hypertension significantly increased, and the hazard ratio and 95% confidence interval were 2.02 (1.35-3.05, P = .001), 2.22 (1.32-3.76, P = .003), and 7.20 (4.52-11.48, P < .001), respectively. Hcy improved the predictive capability of traditional risk factors for stroke. The optimal cut-off value of Hcy for predicting stroke was 13.4 μmol/L (sensitivity: 70.9%, specificity: 62.2%).Hcy 10 to 15 μmol/L is significantly associated with the risks for stroke, mortality and major adverse cardiac events, and hypertension. The best cut-off point of Hcy for predicting stroke is 13.4 μmol/L.

Fresh fruit consumption may decrease the long-term risk of esophageal cancer mortality: A 30-year follow-up study in the Linxian Dysplasia Nutrition Intervention trial (NIT)

BACKGROUND

The objective of this study was to explore the association between fresh fruit consumption and long-term risk of upper gastrointestinal cancer (UGI) in the Linxian Dysplasia Nutrition Intervention Trial (NIT) cohort.

METHODS

A cohort of 3318 subjects with esophageal squamous dysplasia participated in the Linxian Dysplasia NIT in May 1985 and were followed up until 30 September 2015. Demographic characteristics, lifestyle, and history of diseases were collected at the baseline. The primary endpoint was death from esophageal squamous cell carcinoma (ESCC), gastric cardia carcinoma (GCC), and gastric noncardia carcinoma (GNCC). Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were estimated using the Cox proportional hazard model.

RESULTS

In the 30-year follow-up, a total of 541 ESCC, 284 GCC, and 77 GNCC deaths occurred. Relative to those who never or rarely consumed fresh fruit, the risk of ESCC mortality in participants who consumed fresh fruit more than 12 times/year were significantly decreased by 37.3% (HR = 0.63, 95% CI: 0.49-0.81). In the subgroup analyses, significantly protective effects on ESCC mortality were observed especially in females (HR = 0.59, 95% CI: 0.40-0.89), non-smokers (HR = 0.67, 95% CI: 0.48-0.94), and nondrinkers (HR = 0.69, 95% CI: 0.51-0.93).

CONCLUSIONS

Consuming fresh fruit more than 12 times/year may reduce the long-term risk of ESCC mortality in this dysplasia population, particularly in females, non-smokers, and nondrinkers. Future studies are needed to confirm these findings.

Serum levels of carotenoids in patients with osteonecrosis of the femoral head are lower than in healthy, community-living people

PURPOSE

Oxidative stress is closely associated with the pathogenesis of nontraumatic osteonecrosis of the femoral head (ONFH). This study aimed to determine whether the serum levels of antioxidant nutrients were decreased in patients with ONFH.

METHODS

We analyzed the serum levels of antioxidant nutrients in 39 patients with ONFH (ONFH group) and 78 age- and gender-matched healthy people (control group) who voluntarily participated in the Yakumo study, which is a comprehensive health examination program. We measured and compared the serum levels of α-tocopherol (vitamin E) and total carotenoids, including zeaxanthin/lutein, β-cryptoxanthin, lycopene, α-carotene, and β-carotene, in the ONFH and control groups using high-performance liquid chromatography.

RESULTS

The mean serum levels of total carotenoids were significantly lower in the ONFH group than in the control group (2.36 ± 1.26 and 3.79 ± 2.36 µmol/l, respectively, p < 0.001). However, no significant difference was found in α-tocopherol between the two groups (26.37 ± 6.90 µmol/l in the ONFH group and 26.24 ± 6.28 µmol/l in the control group, p = 0.920). Among each carotenoid, the serum levels of zeaxanthin/lutein, lycopene, and β-carotene were significantly lower in the ONFH group than in the control group ( p < 0.001).

CONCLUSIONS

The serum levels of carotenoids were lower in patients with ONFH than in healthy, community-living people. This result suggests that carotenoids may be related to the pathogenesis of ONFH.

High dietary total antioxidant capacity is associated with a reduced risk of hypertension in French women

Background

Although there is evidence for a reduced risk of hypertension associated with fruit and vegetable consumption, the relationship between the total antioxidant capacity of the diet (TAC) and the risk of hypertension has not been previously examined. We aimed to evaluate that association in the large E3N French prospective cohort of women.

Methods

Dietary TAC was estimated using total radical-trapping ability parameter (TRAP) assay food values; self-reported incident hypertension cases were validated. Cox regression models were adjusted for conventional risk factors, body mass index, physical activity, energy, sodium, magnesium, omega-3 fatty acids, and alcohol.

Results

After an average 12.7 years of follow up, there were 9350 incident cases of hypertension among 40,576 women. Dietary TAC was inversely associated with the risk of hypertension with a 15% lower risk of hypertension in those in the fifth vs. first quintile (HR_Q5 0.85 [CI 95% 0.74; 0.95] p-trend 0.03) An inverse dose-effect relationship was observed for dietary TAC excluding coffee (HR_Q5 0.85 [CI 95% 0.74; 0.95], p-trend 0.0008), while for dietary TAC from coffee, only the highest quintile was inversely associated with risk (HR_Q5 0.86 [0.75, 0.97], p-trend 0.20). In a fully partitioned model with major dietary TAC contributors, TAC from fruit/vegetables, wine, and miscellaneous sources was inversely associated with risk, while associations with TAC from coffee, tea, and chocolate were not statistically significant.

Conclusions

In a large prospective cohort, the risk of incident hypertension in women was inversely associated with the antioxidant capacity of the diet, suggesting that promoting a diet naturally rich in antioxidants might help prevent the development of hypertension.

Electronic supplementary material

The online version of this article (10.1186/s12937-019-0456-0) contains supplementary material, which is available to authorized users.

Effects of Multivitamin and Multimineral Supplementation on Blood Pressure: A Meta-Analysis of 12 Randomized Controlled Trials

Previous studies have not drawn a consistent conclusion about effect of multivitamin and multimineral supplementation (MVMS) on blood pressure. A comprehensive search of PubMed, Embase and Cochrane Library (up to May 2018) and references of relevant articles was undertaken. The present meta-analysis included 12 randomized controlled trials (RCTs), of which eight RCTs in 2011 subjects evaluated the effect of MVMS on blood pressure and four RCTs in 21,196 subjects evaluated the effect of MVMS on the risk of hypertension. MVMS had a lowering effect on systolic blood pressure (SBP) and diastolic blood pressure (DBP): the weighted mean difference (WMD) was -1.31 mmHg (95% CI, -2.48 to -0.14 mmHg) and -0.71 mmHg (95% CI, -1.43 to 0.00 mmHg), respectively. Subgroup analysis indicated that the lowering effect of MVMS on blood pressure was only significant in 134 subjects with chronic disease but not in 1580 healthy subjects, and the WMD for systolic blood pressure (SBP) and DBP in subjects with chronic disease was -6.29 mmHg (95% CI, -11.09 to -1.50 mmHg) and -2.32 mmHg (95% CI, -4.50 to -0.13 mmHg), respectively. The effect size of MVMS on SBP in 58 hypertensive subjects (WMD, -7.98 mmHg; 95% CI, -14.95 to -1.02 mmHg) was more than six times of that in 1656 normotensive subjects (WMD, -1.25 mmHg; 95% CI, -2.48 to -0.02 mmHg). However, no significant effect on DBP was observed in both hypertensive and normotensive subgroups. There was no significant effect of MVMS on risk of hypertension in 22,852 subjects with a normal blood pressure at baseline. In conclusion, although MVMS had a significant lowering effect on blood pressure in normotensive subjects, the lowering effect was too small to effectively prevent future hypertension. MVMS may be an effective method for blood pressure control in subjects with chronic disease including hypertension, but the sample size of subjects with hypertension or other chronic disease was too small, and more well-designed RCTs are needed to confirm this result.

Antioxidant effects of vitamins in type 2 diabetes: a meta-analysis of randomized controlled trials

BACKGROUND

Vitamins are essential micronutrients with antioxidant potential that may provide a complementary treatment for patients with chronic diseases. Our aim was to assess the effect of vitamin supplementation on the antioxidant status and glycemic index of type 2 diabetes mellitus patients.

METHODS

We performed a systematic review with meta-analyses. Electronic searches were conducted in PubMed, Scopus, and Web of Science (December 2017). Randomized controlled trials evaluating the effect of any vitamin or vitamin complex supplementation on antioxidant status as primary outcome were included. The outcomes considered were: reduction of malondialdehyde (MDA); augmentation of glutathione peroxidase (GPx); changes in total antioxidant capacity (TAC), enhance in superoxide dismutase enzyme-SOD, and thiobarbituric acid reactive substances (TBARS). Outcomes of glycemic control were also evaluated. Pairwise meta-analyses were performed using software Review Manager 5.3.

RESULTS

Thirty trials fulfilled the inclusion criteria, but only 12 could be included in the meta-analyses of antioxidant outcomes. The most commonly studied vitamins were B, C, D and E. Vitamin E was related to significant reduction of blood glucose as well as glycated hemoglobin compared to placebo, while both vitamins C and E were mainly associated with reducing MDA and TBARS and elevating GPx, SOD and TAC, compared to placebo. However, outcome reports in this field are still inconsistent (e.g. because of a lack of standard measures).

CONCLUSIONS

Supplementation of vitamin E may be a valuable strategy for controlling diabetes complications and enhancing antioxidant capacity. The effects of other micronutrients should be further investigated in larger and well-designed trials to properly place these complementary therapies in clinical practice.

Folic Acid in Stroke Prevention in Countries without Mandatory Folic Acid Food Fortification: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND AND PURPOSE

Additional folic acid (FA) treatment appears to have a neutral effect on reducing vascular risk in countries that mandate FA fortification of food (e.g., USA and Canada). However, it is uncertain whether FA therapy reduces stroke risk in countries without FA food fortification. The purpose of this study was to comprehensively evaluate the efficacy of FA therapy on stroke prevention in countries without FA food fortification.

METHODS

PubMed, EMBASE, and clinicaltrials.gov from January 1966 to August 2016 were searched to identify relevant studies. Relative risk (RR) with 95% confidence interval (CI) was used as a measure of the association between FA supplementation and risk of stroke, after pooling data across trials in a random-effects model.

RESULTS

The search identified 13 randomized controlled trials (RCTs) involving treatment with FA that had enrolled 65,812 participants, all of which stroke was reported as an outcome measure. After all 13 RCTs were pooled, FA therapy versus control was associated with a lower risk of any future stroke (RR, 0.85; 95% CI, 0.77 to 0.95). FA alone or combination of FA and minimal cyanocobalamin (≤0.05 mg/day) was associated with a lower risk of future stroke (RR, 0.75; 95% CI, 0.66 to 0.86) whereas combination of FA and cyanocobalamin (≥0.4 mg/day) was not associated with a lower risk of future stroke (RR, 0.95; 95% CI, 0.86 to 1.05).

CONCLUSIONS

FA supplement reduced stroke in countries without mandatory FA food fortification. The benefit was found mostly in patients receiving FA alone or combination of FA and minimal cyanocobalamin.

B vitamins in stroke prevention: time to reconsider

B vitamin therapy lowers plasma total homocysteine concentrations, and might be a beneficial intervention for stroke prevention; however, cyanocobalamin (a form of vitamin B12) can accelerate decline in renal function and increase the risk of cardiovascular events in patients with impaired renal function. Although early trials did not show benefit in reduction of stroke, these results might have been due to harm in participants with impaired renal function. In patients with diabetic nephropathy, cyanocobalamin is harmful, whereas B vitamins appear to reduce cardiovascular events in study participants with normal renal function. Our meta-analysis of individual patient data from two large trials of B vitamin therapy (VISP and VITATOPS) indicates that patients with impaired renal function who are exposed to high-dose cyanocobalamin do not benefit from therapy with B vitamins for the prevention of stroke (risk ratio 1·04, 95% CI 0·84-1·27), however, patients with normal renal function who are not exposed to high-dose cyanocobalamin benefit significantly from this treatment (0.78, 0·67-0·90; interaction p=0·03). The potential benefits of B vitamin therapy with folic acid and methylcobalamin or hydroxycobalamin, instead of cyanocobalamin, to lower homocysteine concentrations in people at high risk of stroke warrant further investigation.

Meta-analysis of folic acid efficacy trials in stroke prevention: Insight into effect modifiers

OBJECTIVE

To examine the efficacy and effect modifiers of folic acid supplementation in the prevention of stroke in regions without folic acid fortification based on relevant, up-to-date published randomized trials.

METHODS

Relative risk (RR) was used to measure the effect of folic acid supplementation on risk of stroke using a fixed effects model.

FINDINGS

Overall, folic acid supplementation significantly reduced the stroke risk by 11% (22 trials, n = 82,723; RR 0.89, 95% confidence interval [CI] 0.84-0.96). The effect was greater in low folate regions (2 trials, n = 24,020; Asia, 0.78, 0.67-0.90) compared to high folate regions (7 trials, n = 14,655; America, 1.05, 0.90-1.23), and among patients without folic acid fortification (11 trials, n = 49,957; 0.85; 0.77-0.94) compared with those with folic acid fortification (7 trials, n = 14,655; 1.05, 0.90-1.23). In further stratified analyses among trials without folic acid fortification, a larger beneficial effect was found in those trials that used a low dosage of folic acid (≤0.8 mg: 0.78, 0.69-0.88) or low baseline vitamin B₁₂ levels (<384 pg/mL: 0.78, 0.68-0.89). In the corresponding comparison groups, the effect sizes were attenuated and insignificant (p for interaction <0.05 for both). Although the interaction tests were not significant, there might be a higher benefit in trials with a low dosage of vitamin B₁₂, a low prevalence of statin use, but a high prevalence of hypertension.

CONCLUSIONS

Folic acid supplementation could reduce the stroke risk in regions without folic acid fortification, particularly in trials using a relatively low dosage of folic acid and with low vitamin B₁₂ levels.

Effects of vitamin C supplementation on glycaemic control: a systematic review and meta-analysis of randomised controlled trials

Randomised controlled trials (RCTs) have observed contrasting results on the effects of vitamin C on circulating biomarkers of glycaemic and insulin regulation. We conducted a systematic review and meta-analysis of RCTs testing the effect of vitamin C administration on glucose, HbA1c and insulin concentrations. Four databases (PubMed, Embase, Scopus and Cochrane Library) were used to retrieve RCTs published from inception until April 2016 and testing the effects of vitamin C in adult participants. The screening of 2008 articles yielded 22 eligible studies (937 participants). Overall, vitamin C did not modify glucose, HbA1c and insulin concentrations. However, subgroup analyses showed that vitamin C significantly reduced glucose concentrations (-0.44 mmol/l, 95% CI: -0.81, -0.07, P=0.01) in patients with type 2 diabetes and in interventions with a duration greater than 30 days (-0.53%, 95% CI: -0.79, -0.10, P=0.02). Vitamin C administration had greater effects on fasting (-13.63 pmol/l, 95% CI: -22.73, -4.54, P<0.01) compared to postprandial insulin concentration. Meta-regression analyses showed that age was a modifier of the effect of vitamin C on insulin concentration. Furthermore, the effect size was associated with baseline BMI and plasma glucose levels, and with the duration of the intervention. In conclusion, greater reduction in glucose concentrations observed in patients with diabetes, older individuals and with more prolonged supplementation. Personalised interventions with vitamin C may represent a feasible future strategy to enhance benefits and efficacy of interventions. Nevertheless, results need to be interpreted cautiously due to limitations in the primary studies analysed.

Folic Acid Supplementation and the Risk of Cardiovascular Diseases: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Results from observational and genetic epidemiological studies suggest that lower serum homocysteine levels are associated with lower incidence of cardiovascular disease (CVD). Numerous randomized controlled trials have investigated the efficacy of lowering homocysteine with folic acid supplementation for CVD risk, but conflicting results have been reported.

METHODS AND RESULTS

Three bibliographic databases (Medline, Embase, and the Cochrane Database of Systematic Reviews) were searched from database inception until December 1, 2015. Of the 1933 references reviewed for eligibility, 30 randomized controlled trials involving 82 334 participants were included in the final analysis. The pooled relative risks of folic acid supplementation compared with controls were 0.90 (95% CI 0.84-0.96; P=0.002) for stroke, 1.04 (95% CI 0.99-1.09; P=0.16) for coronary heart disease, and 0.96 (95% CI 0.92-0.99; P=0.02) for overall CVD. The intervention effects for both stroke and combined CVD were more pronounced among participants with lower plasma folate levels at baseline (both P<0.02 for interaction). In stratified analyses, a greater beneficial effect for overall CVD was seen in trials among participants without preexisting CVD (P=0.006 for interaction) or in trials with larger reduction in homocysteine levels (P=0.009 for interaction).

CONCLUSIONS

Our meta-analysis indicated a 10% lower risk of stroke and a 4% lower risk of overall CVD with folic acid supplementation. A greater benefit for CVD was observed among participants with lower plasma folate levels and without preexisting CVD and in studies with larger decreases in homocysteine levels. Folic acid supplementation had no significant effect on risk of coronary heart disease.

Multivitamin use and the risk of hypertension in a prospective cohort study of women

OBJECTIVE

Despite the widespread use of multivitamin supplements, little is known regarding their effects on blood pressure (BP) and the development of hypertension. We, therefore, sought to prospectively investigate how multivitamin use was associated with incident hypertension among middle-aged and older women.

METHODS

We studied 28 157 women from the Women's Health Study aged at least 45 years and free of cardiovascular disease, cancer, and hypertension at baseline. Women reported information on a wide range of lifestyle, clinical, and dietary factors, including multivitamin and other supplement use at baseline. Hypertension was identified on baseline and annual follow-up questionnaires. Incident hypertension was defined as either a new diagnosis of hypertension by a physician, initiation of antihypertensive medication, newly reported SBP at least 140 mmHg, or DBP at least 90 mmHg during follow-up.

RESULTS

During a mean follow-up of 11.5 years, we identified 16 316 cases of incident hypertension. We found that neither baseline (hazard ratio = 1.03, 95% confidence interval: 1.00, 1.07) nor time-varying multivitamin use (hazard ratio = 0.97, 95% confidence interval: 0.94-1.00) were associated with the risk of incident hypertension in multivariable-adjusted models. When we investigated the duration of multivitamin use reported at baseline, we also observed no association with the risk of hypertension.

CONCLUSION

The results from this prospective study of middle-aged and older women suggest that neither baseline multivitamin use nor time-varying multivitamin use is associated with the risk of developing hypertension.

Effect of supplementation of water-soluble vitamins on oxidative stress and blood pressure in prehypertensives

The objective of the study was to evaluate the effect of water-soluble vitamins on oxidative stress and blood pressure in prehypertensives. Sixty prehypertensives were recruited and randomized into 2 groups of 30 each. One group received water-soluble vitamins and the other placebo for 4 months. Further increase in blood pressure was not observed in the vitamin group which increased significantly in the placebo group at the end of 4 months. Malonedialdehyde and protein carbonylation were reduced during the course of treatment with vitamins whereas in the placebo group there was an increase in the level of malondialdehyde. In conclusion, supplementation of water-soluble vitamins in prehypertension reduces oxidative stress and its progression to hypertension.

Homocysteine, Ischemic Stroke, and Coronary Heart Disease in Hypertensive Patients

Background and Purpose—

Total homocysteine level (tHcy) is a risk factor of ischemic stroke (IS) and coronary heart disease. However, the results are conflicting and mainly focused on healthy individuals in developed countries.

Methods—

A prospective, population-based cohort study was conducted among 5935 participants from 60 communities in the city of Shenzhen, China. A Cox regression analysis was applied to evaluate the contribution of tHcy to the risk of IS and coronary heart disease. The effect of folic acid supplementation on tHcy levels was also evaluated among 501 patients with essential hypertension, who received an average of 2.5 years of folic acid supplementation.

Results—

After adjustment for confounding factors, the hazard ratios (95% confidence intervals) of IS caused by hyperhomocysteinemia were 2.18 (1.65–2.89), 2.40 (1.56–3.67), and 2.73 (1.83–4.08) in the total, male, and female participants, respectively. Compared with normal levels of tHcy (<15 μmol/L), the hazard ratios (95% confidence intervals) for IS in the highest tHcy category (≥30 μmol/L) were 4.96 (3.03–8.12), 6.11 (3.44–10.85), and 1.84 (0.52–6.46) in the total, males, and females participants, respectively. However, we did not observe a significant relationship between tHcy and the risk of coronary heart disease. The 2.5 years of folic acid supplementation reduced tHcy levels by 6.7 μmol/L (27.92%) in patients with essential hypertension.

Conclusions—

Hyperhomocysteinemia in Chinese hypertensive patients is significantly associated with IS risk but not coronary heart disease susceptibility, and folic acid supplementation can efficiently reduce tHcy levels.

Effect of vitamin C and vitamin E supplementation on endothelial function: a systematic review and meta-analysis of randomised controlled trials

Randomised controlled trials (RCT) testing the effects of antioxidant supplements on endothelial function (EF) have reported conflicting results. We aimed to investigate the effects of supplementation with antioxidant vitamins C and E on EF and to explore factors that may provide explanations for the inconsistent results. We searched four databases (MEDLINE, Embase, Cochrane Library and Scopus) from inception until May 2014 for RCT involving adult participants aged ≥18 years who were supplemented with vitamins C and E alone or in combination for more than 2 weeks and reporting changes in EF measured using flow mediated dilation or forearm blood flow. Data were pooled as standardised mean difference (SMD) and analysed using a random-effects model. Significant improvements in EF were observed in trials supplementing with vitamin C alone (500-2000 mg/d) (SMD: 0·25, 95% CI 0·02, 0·49, P=0·043) and vitamin E alone (300-1800 IU/d; 1 IU vitamin E=0·67 mg natural vitamin E) (SMD: 0·48, 95% CI 0·23, 0·72, P=0·0001), whereas co-administration of both vitamins was ineffective (vitamin C: 500-2000 mg/d; vitamin E: 400-1200 IU/d) (SMD: 0·12, 95% CI-0·18, 0·42, P=0·428). The effect of vitamin C supplementation on EF increased significantly with age (β 0·023, 95% CI 0·001, 0·05, P=0·042). There was a significant negative correlation between baseline plasma vitamin E concentration and the effect of vitamin E supplementation on EF (β-0·03, 95% CI-0·06, -0·001, P=0·029). Supplementation with either vitamin C or vitamin E alone improves EF. However, subgroup analysis emphasises the importance of careful characterisation and selection of a population group which may benefit from such supplementation.

Systematic review and meta-analysis of randomised controlled trials testing the effects of vitamin C supplementation on blood lipids

BACKGROUND & AIMS

Randomised controlled trials (RCTs) in humans revealed contradictory results regarding the effect of vitamin C supplementation on blood lipids. We aimed to conduct a systematic review and meta-analysis of RCTs investigating the effect of vitamin C supplementation on total cholesterol, low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C) and triglycerides and to determine whether the effects are modified by the participants' or intervention characteristics.

METHODS

Four databases (PubMed, Embase, Scopus and Cochrane Library) were searched from inception until August 2014 for RCTs supplementing adult participants with vitamin C for ≥ 2 weeks and reporting changes in blood lipids.

RESULTS

Overall, vitamin C supplementation did not change blood lipids concentration significantly. However, supplementation reduced total cholesterol in younger participants (≤52 years age) (-0.26 mmol/L, 95% CI: -0.45, -0.07) and LDL-C in healthy participants (-0.32 mmol/L, 95% CI: -0.57, -0.07). In diabetics, vitamin C supplementation reduced triglycerides significantly (-0.15 mmol/L, 95% CI: -0.30, -0.002) and increased HDL-C significantly (0.06 mmol/L, 95% CI: 0.02, 0.11). Meta-regression analyses showed the changes in total cholesterol (β: -0.24, CI: -0.36, -0.11) and in triglycerides (β: -0.17, CI: -0.30, -0.05) following vitamin C supplementation were greater in those with higher concentrations of these lipids at baseline. Greater increase in HDL-C was observed in participants with lower baseline plasma concentrations of vitamin C (β: -0.002, CI: -0.003, -0.0001).

CONCLUSIONS

Overall, vitamin C supplementation had no significant effect on lipid profile. However, subgroup and sensitivity analyses showed significant reductions in blood lipids following supplementation in sub-populations with dyslipidaemia or low vitamin C status at baseline. PROSPERO Database registration: CRD42014013487, http://www.crd.york.ac.uk/prospero/.

The effect of folate fortification on folic acid-based homocysteine-lowering intervention and stroke risk: a meta-analysis

OBJECTIVE

Folate and vitamin B12 are two vital regulators in the metabolic process of homocysteine, which is a risk factor of atherothrombotic events. Low folate intake or low plasma folate concentration is associated with increased stroke risk. Previous randomized controlled trials presented discordant findings in the effect of folic acid supplementation-based homocysteine lowering on stroke risk. The aim of the present review was to perform a meta-analysis of relevant randomized controlled trials to check the how different folate fortification status might affect the effects of folic acid supplementation in lowering homocysteine and reducing stroke risk.

DESIGN

Relevant randomized controlled trials were identified through formal literature search. Homocysteine reduction was compared in subgroups stratified by folate fortification status. Relative risks with 95 % confidence intervals were used as a measure to assess the association between folic acid supplementation and stroke risk.

SETTING

The meta-analysis included fourteen randomized controlled trials,

SUBJECTS

A total of 39 420 patients.

RESULTS

Homocysteine reductions were 26·99 (sd 1·91) %, 18·38 (sd 3·82) % and 21·30 (sd 1·98) %, respectively, in the subgroups without folate fortification, with folate fortification and with partial folate fortification. Significant difference was observed between the subgroups with folate fortification and without folate fortification (P=0·05). The relative risk of stroke was 0·88 (95 % CI 0·77, 1·00, P=0·05) in the subgroup without folate fortification, 0·94 (95 % CI 0·58, 1·54, P=0·82) in the subgroup with folate fortification and 0·91 (95 % CI 0·82, 1·01, P=0·09) in the subgroup with partial folate fortification.

CONCLUSIONS

Folic acid supplementation might have a modest benefit on stroke prevention in regions without folate fortification.

The role of homocysteine-lowering B-vitamins in the primary prevention of cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of mortality in the Western world. The effort of research should aim at the primary prevention of CVD. Alongside statin therapy, which is maintained to be an effective method of CVD prevention, there are alternative methods such as vitamin B substitution therapy with folic acid (FA), and vitamins B12 and B6 . B-vitamins may inhibit atherogenesis by decreasing the plasma level of homocysteine (Hcy)-a suspected etiological factor for atherosclerosis-and by other mechanisms, primarily through their antioxidant properties. Although Hcy-lowering vitamin trials have failed to demonstrate beneficial effects of B-vitamins in the prevention of CVD, a meta-analysis and stratification of a number of large vitamin trials have suggested their effectiveness in cardiovascular prevention (CVP) in some aspects. Furthermore, interpretation of the results from these large vitamin trials has been troubled by statin/aspirin therapy, which was applied along with the vitamin substitution, and FA fortification, both of which obscured the separate effects of vitamins in CVP. Recent research results have accentuated a new approach to vitamin therapy for CVP. Studies undertaken with the aim of primary prevention have shown that vitamin B substitution may be effective in the primary prevention of CVD and may also be an option in the secondary prevention of disease if statin therapy is accompanied by serious adverse effects. Further investigations are needed to determine the validity of vitamin substitution therapy before its introduction in the protocol of CVD prevention.

Antioxidant vitamin supplementation reduces arterial stiffness in adults: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Several studies tested the effects of supplementation with antioxidant vitamins on arterial stiffness, but the results were contradictory.

OBJECTIVES

The aim of our study was to conduct a systematic review and meta-analysis investigating the effect of antioxidant vitamins on arterial stiffness and to determine whether the effects on arterial stiffness vary according to dose, duration of intervention, and health or nutritional status of the included participants.

METHODS

We searched 3 databases (Medline, Embase, and Scopus) for articles that potentially met the following eligibility criteria: 1) randomized controlled trials comparing antioxidant vitamins (vitamins C, E, and A and β-carotene) to either placebo or no active control in 2) adult participants aged ≥18 y; 3) antioxidant vitamins administered alone or in combination, irrespective of dose, duration, and route of administration; and 4) changes in arterial stiffness or arterial compliance. Data were pooled as standardized mean differences (SMDs) and analyzed using fixed- and random-effects models.

RESULTS

Data synthesis showed that antioxidant vitamins reduced arterial stiffness significantly (SMD: -0.17; 95% CI: -0.26, -0.08; P < 0.001). This effect was significant in experimental (SMD: -1.02; 95% CI: -1.54, -0.49; P < 0.001) and primary prevention (SMD: -0.14; 95% CI: -0.24, -0.04; P < 0.01) studies, whereas a trend for reduced arterial stiffness was observed in studies including participants with diseases (SMD: -0.19; 95% CI: -0.40, 0.02; P = 0.08). Vitamin supplementation improved arterial stiffness irrespective of age group and duration of intervention. Antioxidant vitamins were more effective in participants with low baseline plasma concentrations of vitamins C (SMD: -0.35; 95% CI: -0.62, -0.07; P < 0.016) and E (SMD: -0.79; 95% CI: -1.23, -0.33; P < 0.01).

CONCLUSIONS

Supplementation with antioxidant vitamins has a small, protective effect on arterial stiffness. The effect may be augmented in those with lower baseline plasma vitamin E and C concentrations. This trial was registered at PROSPERO as CRD42014007260.

Elevated plasma homocysteine level is associated with ischemic stroke in Chinese hypertensive patients

BACKGROUND

Accumulating data suggest that hyperhomocysteinemia is associated with the risk of ischemic stroke (IS) and coronary heart disease (CHD) in the general population, but the relationship remains unclear in hypertensive patients. We examined the association of total homocysteine (tHcy) with IS and CHD in hypertensive patients.

METHODS

A total of 5935 Chinese hypertensive patients were recruited in a community-based cross-sectional study from 60 communities in Shenzhen, China. Plasma tHcy was quantitatively measured using the enzyme cycle method. Conventional risk factors for IS and CHD were obtained through questionnaire interviews and physical examinations. We included cerebral infarction, embolism and small-vessel disease as IS; and myocardial infarction, angina pectoris, coronary revascularization, and cardiac arrest as CHD. IS and CHD were retrospectively adjudicated by specialists via interviews, hospital records or relevant tests.

RESULTS

Significantly higher values of tHcy were observed in IS patients than in non-IS controls among both men and women. Greater tHcy level was dose dependently associated with an increased risk of IS presence in women, men and them combined (p-trend: 0.002, 3.8×10(-4) and 0.001). The odds ratios (95% CI) of IS for tHcy ≥30 (vs. <15) μmol/L were 2.84 (1.73-4.34) in men, 4.41 (1.62-9.15) in women, and 2.86 (1.72-4.75) in their combination after adjusting for other main risk factors of IS. We did not find any significant association between tHcy and presence of CHD after the adjustment for covariates.

CONCLUSIONS

Plasma homocysteine level is positively associated with the presence of IS, but not CHD, in Chinese hypertensive patients.

Regulatory metabolites of vitamin E and their putative relevance for atherogenesis

Vitamin E is likely the most important antioxidant in the human diet and α-tocopherol is the most active isomer. α-Tocopherol exhibits anti-oxidative capacity in vitro, and inhibits oxidation of LDL. Beside this, α-tocopherol shows anti-inflammatory activity and modulates expression of proteins involved in uptake, transport and degradation of tocopherols, as well as the uptake, storage and export of lipids such as cholesterol. Despite promising anti-atherogenic features in vitro, vitamin E failed to be atheroprotective in clinical trials in humans. Recent studies highlight the importance of long-chain metabolites of α-tocopherol, which are formed as catabolic intermediate products in the liver and occur in human plasma. These metabolites modulate inflammatory processes and macrophage foam cell formation via mechanisms different than that of their metabolic precursor α-tocopherol and at lower concentrations. Here we summarize the controversial role of vitamin E as a preventive agent against atherosclerosis and point the attention to recent findings that highlight a role of these long-chain metabolites of vitamin E as a proposed new class of regulatory metabolites. We speculate that the metabolites contribute to physiological as well as pathophysiological processes.

Folic acid supplementation with and without vitamin B6 and revascularization risk: a meta-analysis of randomized controlled trials

BACKGROUND & AIMS

There is a growing amount of data and a continuing controversy over the effect of folic acid supplementation with and without vitamin B6 on revascularization risk.

METHODS

We conducted a meta-analysis based on up-to-date published relevant randomized trials to further examine this issue. Relative risk (RR) was used to measure the effect of folic acid supplementation on risk of revascularization using a random-effects model. Total revascularization was defined as any arterial revascularization. Restenosis was defined as stenosis of more than 50 percent of the luminal diameter.

RESULTS

Overall, folic acid supplementation had no significant effect on coronary revascularization (9 trials, n = 27,418, RR = 0.99; 95%CI:0.88-1.11, P = 0.88), coronary artery bypass grafting (CABG) (5 trials, n = 10,703, 0.90; 0.79-1.03, P = 0.11), percutaneous coronary intervention (PCI) (5 trials, n = 10,703, 1.05; 0.89-1.23, P = 0.59), coronary restenosis (3 trials, n = 926, 1.05; 0.89-1.23, P = 0.59) or total revascularization (7 trials, n = 29,314, 1.06; 95%CI: 0.99-1.13, P = 0.10). However, a greater beneficial effect was observed for coronary revascularization among those trials with a moderate dose of vitamin B6 (5-10 mg/d; RR: 0.47; 95%CI: 0.28-0.80, P = 0.005), but not in trials without vitamin B6 or with a high dose of vitamin B6. And a non-significant greater total revascularization risk was observed in trials with a higher folic acid dose (>2 mg/d, RR = 1.11; 95%CI: 0.98-1.25, P = 0.09; ≥5 mg/d, RR = 1.98; 95%CI: 0.93-4.20, P = 0.08).

CONCLUSIONS

Our analyses indicate that folic acid supplementation has no significant effect on coronary revascularization, CABG, PCI, coronary restenosis or total revascularization. However, a combination of folic acid and moderate vitamin B6 may be beneficial in reducing coronary revascularization risk.

Does vitamin C deficiency increase lifestyle-associated vascular disease progression? Evidence based on experimental and clinical studies

SIGNIFICANCE

Despite continuous advances in the prevention of cardiovascular disease (CVD), critical issues associated with an unhealthy lifestyle remain an increasing cause of morbidity and mortality in industrialized countries.

RECENT ADVANCES

A growing body of literature supports a specific role for vitamin C in a number of reactions that are associated with vascular function and control including, for example, nitric oxide bioavailability, lipid metabolism, and vascular integrity.

CRITICAL ISSUES

A large body of epidemiological evidence supports a relationship between poor vitamin C status and increased risk of developing CVD, and the prevalence of deficiency continues to be around 10%-20% of the general Western population although this problem could easily and cheaply be solved by supplementation. However, large intervention studies using vitamin C have not found a beneficial effect of supplementation. This review outlines the proposed mechanism by which vitamin C deficiency worsens CVD progression. In addition, it discusses problems with the currently available literature, including the discrepancies between the large intervention studies and the experimental and epidemiological literature.

FUTURE DIRECTIONS

Increased insights into vitamin C deficiency-mediated CVD progression will enable the design of future randomized controlled trials that are better suited to test the efficacy of vitamin C in disease prevention as well as the identification of high-risk individuals which could possibly benefit from supplementation.

Effect of B-vitamin supplementation on stroke: a meta-analysis of randomized controlled trials

Background

B vitamins have been extensively used to reduce homocysteine levels; however, it remains uncertain whether B vitamins are associated with a reduced risk of stroke. Our aim was to evaluate the effects of B vitamins on stroke.

Methodology and Principal findings

We systematically searched PubMed, EmBase, and the Cochrane Central Register of Controlled Trials to identify studies for our analysis. Relative risk (RR) was used to measure the effect of B-vitamin supplementation on the risk of stroke. The analysis was further stratified based on factors that could affect the treatment effects. Of the 13,124 identified articles, we included 18 trials reporting data on 57,143 individuals and 2,555 stroke events. B-vitamin supplementation was not associated with a significant reduction in the risk of stroke (RR, 0.91, 95%CI: 0.82–1.01, P = 0.075; RD, -0.003, 95%CI: -0.007–0.001, P = 0.134). Subgroup analyses suggested that B-vitamin supplementation might reduce the risk of stroke if included trials had a man/woman ratio of more than 2 or subjects received dose of folic acid less than 1 mg. Furthermore, in a cumulative meta-analysis for stroke, the originally proposed nonsignificant B-vitamin effect was refuted by the evidence accumulated up to 2006. There is a small effect with borderline statistical significance based on data gathered since 2007.

Conclusions/Significance

Our study indicates that B-vitamin supplementation is not associated with a lower risk of stroke based on relative and absolute measures of association. Subgroup analyses suggested that B-vitamin supplementation can effectively reduce the risk of stroke if included trials had a man/woman ratio of more than 2 or subjects received dose of folic acid less than 1 mg.

The role of oxidized low-density lipoproteins in atherosclerosis: the myths and the facts

The oxidative modification hypothesis of atherosclerosis, which assigns to oxidized low-density lipoproteins (LDLs) a crucial role in atherosclerosis initiation and progression, is still debated. This review examines the role played by oxidized LDLs in atherogenesis taking into account data derived by studies based on molecular and clinical approaches. Experimental data carried out in cellular lines and animal models of atherosclerosis support the proatherogenic role of oxidized LDLs: (a) through chemotactic and proliferating actions on monocytes/macrophages, inciting their transformation into foam cells; (b) through stimulation of smooth muscle cells (SMCs) recruitment and proliferation in the tunica intima; (c) through eliciting endothelial cells, SMCs, and macrophages apoptosis with ensuing necrotic core development. Moreover, most of the experimental data on atherosclerosis-prone animals benefiting from antioxidant treatment points towards a link between oxidative stress and atherosclerosis. The evidence coming from cohort studies demonstrating an association between oxidized LDLs and cardiovascular events, notwithstanding some discrepancies, seems to point towards a role of oxidized LDLs in atherosclerotic plaque development and destabilization. Finally, the results of randomized clinical trials employing antioxidants completed up to date, despite demonstrating no benefits in healthy populations, suggest a benefit in high-risk patients. In conclusion, available data seem to validate the oxidative modification hypothesis of atherosclerosis, although additional proofs are still needed.

Efficacy of vitamin and antioxidant supplements in prevention of cardiovascular disease: systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To assess the efficacy of vitamin and antioxidant supplements in the prevention of cardiovascular diseases.

DESIGN

Meta-analysis of randomised controlled trials.

DATA SOURCES AND STUDY SELECTION

PubMed, EMBASE, the Cochrane Library, Scopus, CINAHL, and ClinicalTrials.gov searched in June and November 2012. Two authors independently reviewed and selected eligible randomised controlled trials, based on predetermined selection criteria.

RESULTS

Out of 2240 articles retrieved from databases and relevant bibliographies, 50 randomised controlled trials with 294,478 participants (156,663 in intervention groups and 137,815 in control groups) were included in the final analyses. In a fixed effect meta-analysis of the 50 trials, supplementation with vitamins and antioxidants was not associated with reductions in the risk of major cardiovascular events (relative risk 1.00, 95% confidence interval 0.98 to 1.02; I(2)=42%). Overall, there was no beneficial effect of these supplements in the subgroup meta-analyses by type of prevention, type of vitamins and antioxidants, type of cardiovascular outcomes, study design, methodological quality, duration of treatment, funding source, provider of supplements, type of control, number of participants in each trial, and supplements given singly or in combination with other supplements. Among the subgroup meta-analyses by type of cardiovascular outcomes, vitamin and antioxidant supplementation was associated with a marginally increased risk of angina pectoris, while low dose vitamin B(6) supplementation was associated with a slightly decreased risk of major cardiovascular events. Those beneficial or harmful effects disappeared in subgroup meta-analysis of high quality randomised controlled trials within each category. Also, even though supplementation with vitamin B(6) was associated with a decreased risk of cardiovascular death in high quality trials, and vitamin E supplementation with a decreased risk of myocardial infarction, those beneficial effects were seen only in randomised controlled trials in which the supplements were supplied by the pharmaceutical industry.

CONCLUSION

There is no evidence to support the use of vitamin and antioxidant supplements for prevention of cardiovascular diseases.

Efficacy of folic acid supplementation in cardiovascular disease prevention: an updated meta-analysis of randomized controlled trials

BACKGROUND

In observational studies, lower serum homocysteine levels are associated with a lower incidence of cardiovascular disease (CVD). However, individual randomized controlled trials (RCTs) have yielded mixed findings regarding the efficacy of therapeutic homocysteine in lowering cardiovascular risk. Our aim was to perform an updated meta-analysis of relevant RCTs to assess the efficacy of folic acid supplementation in the prevention of CVD, coronary heart disease (CHD), and stroke.

METHODS

We performed systematic search to identify RCTs reported at least one of the CVD, CHD, or stroke as outcomes. Relative risk (RR) with 95% confidence interval was used as a measure of the association between folic acid supplementation and risk of CVD, CHD, stroke, and all-cause mortality. The analysis was further stratified by factors that could affect the treatment effects.

RESULTS

The systematic search identified 26 RCTs enrolling 58,804 participants. Pooling the RRs showed that folic acid supplementation was not associated with any significant change in the risk of CVD (RR 0.98, 0.95 to 1.02; p=0.36), CHD (RR 1.03, 0.98 to 1.08; p=0.23), and all-cause mortality (RR 1.00, 0.96 to 1.04; p=0.92), but was linked to a decreasing trend in stroke risk (RR 0.93, 0.86 to 1.00; p=0.05). In stratified analyses, the only heterogeneity was found for stroke risk reduction among groups with (RR 1.07, 0.92 to 1.25) vs. without (RR 0.88, 0.81 to 0.96) mandatory grain fortification (P for heterogeneity=0.03).

CONCLUSIONS

This meta-analysis suggests that there might be a potentially modest benefit of folic acid supplementation in stroke prevention.

Efficacy of folic acid supplementation in stroke prevention: new insight from a meta-analysis

AIMS

  There are growing data and a continuing controversy over the efficacy of folic acid supplementation in stroke prevention. We conducted a meta-analysis based on relevant, up-to-date published randomised trials to further examine this issue.

METHODS

  Relative risk (RR) was used to measure the effect of folic acid supplementation on risk of stroke with a fixed-effects model.

RESULTS

  Overall, folic acid supplementation reduced the risk of stroke by 8% (n = 55,764; RR: 0.92; 95% CI: 0.86-1.00, p = 0.038). In the 10 trials with no or partial folic acid fortification (n = 43,426), the risk of stroke was reduced by 11% (0.89; 0.82-0.97, p = 0.010). Within these trials, a greater beneficial effect was observed among trials with a lower percent use of statins [≤ 80% (median); 0.77; 0.64-0.92, p = 0.005], and a meta-regression analysis also suggested a positive dose-response relationship between percent use of statins and log-RR for stroke associated with folic acid supplementation (p = 0.013). A daily dose of 0.4-0.8mg folic acid appeared to be adequate for stroke prevention in comparison with larger doses. In the remaining five trials conducted in populations with folic acid fortification (n = 12,338), folic acid supplementation had no effect on stroke risk (1.03; 0.88-1.21, 0.69).

CONCLUSIONS

  Our analysis indicated that folic acid supplementation is effective in stroke prevention in populations with no or partial folic acid fortification. In addition, a greater beneficial effect was observed among trials with a lower percent use of statins. Our findings underscore the importance of identifying target populations that can particularly benefit from folic acid therapy.

Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials

BACKGROUND

In observational studies, increased vitamin C intake, vitamin C supplementation, and higher blood concentrations of vitamin C are associated with lower blood pressure (BP). However, evidence for blood pressure-lowering effects of vitamin C in clinical trials is inconsistent.

OBJECTIVE

The objective was to conduct a systematic review and meta-analysis of clinical trials that examined the effects of vitamin C supplementation on BP.

DESIGN

We searched Medline, EMBASE, and Central databases from 1966 to 2011. Prespecified inclusion criteria were as follows: 1) use of a randomized controlled trial design; 2) trial reported effects on systolic BP (SBP) or diastolic BP (DBP) or both; 3) trial used oral vitamin C and concurrent control groups; and 4) trial had a minimum duration of 2 wk. BP effects were pooled by random-effects models, with trials weighted by inverse variance.

RESULTS

Twenty-nine trials met eligibility criteria for the primary analysis. The median dose was 500 mg/d, the median duration was 8 wk, and trial sizes ranged from 10 to 120 participants. The pooled changes in SBP and DBP were -3.84 mm Hg (95% CI: -5.29, -2.38 mm Hg; P < 0.01) and -1.48 mm Hg (95% CI: -2.86, -0.10 mm Hg; P = 0.04), respectively. In trials in hypertensive participants, corresponding reductions in SBP and DBP were -4.85 mm Hg (P < 0.01) and -1.67 mm Hg (P = 0.17). After the inclusion of 9 trials with imputed BP effects, BP effects were attenuated but remained significant.

CONCLUSIONS

In short-term trials, vitamin C supplementation reduced SBP and DBP. Long-term trials on the effects of vitamin C supplementation on BP and clinical events are needed.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Our systematic review has demonstrated that antioxidant supplements may increase mortality. We have now updated this review.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements for prevention of mortality in adults.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index Expanded, and Conference Proceedings Citation Index-Science to February 2011. We scanned bibliographies of relevant publications and asked pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Random-effects and fixed-effect model meta-analyses were conducted. Risk of bias was considered in order to minimise the risk of systematic errors. Trial sequential analyses were conducted to minimise the risk of random errors. Random-effects model meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Seventy-eight randomised trials with 296,707 participants were included. Fifty-six trials including 244,056 participants had low risk of bias. Twenty-six trials included 215,900 healthy participants. Fifty-two trials included 80,807 participants with various diseases in a stable phase. The mean age was 63 years (range 18 to 103 years). The mean proportion of women was 46%. Of the 78 trials, 46 used the parallel-group design, 30 the factorial design, and 2 the cross-over design. All antioxidants were administered orally, either alone or in combination with vitamins, minerals, or other interventions. The duration of supplementation varied from 28 days to 12 years (mean duration 3 years; median duration 2 years). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects model meta-analysis (21,484 dead/183,749 (11.7%) versus 11,479 dead/112,958 (10.2%); 78 trials, relative risk (RR) 1.02, 95% confidence interval (CI) 0.98 to 1.05) but significantly increased mortality in a fixed-effect model (RR 1.03, 95% CI 1.01 to 1.05). Heterogeneity was low with an I(2)- of 12%. In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. Meta-regression analysis did not find a significant difference in the estimated intervention effect in the primary prevention and the secondary prevention trials. In the 56 trials with a low risk of bias, the antioxidant supplements significantly increased mortality (18,833 dead/146,320 (12.9%) versus 10,320 dead/97,736 (10.6%); RR 1.04, 95% CI 1.01 to 1.07). This effect was confirmed by trial sequential analysis. Excluding factorial trials with potential confounding showed that 38 trials with low risk of bias demonstrated a significant increase in mortality (2822 dead/26,903 (10.5%) versus 2473 dead/26,052 (9.5%); RR 1.10, 95% CI 1.05 to 1.15). In trials with low risk of bias, beta-carotene (13,202 dead/96,003 (13.8%) versus 8556 dead/77,003 (11.1%); 26 trials, RR 1.05, 95% CI 1.01 to 1.09) and vitamin E (11,689 dead/97,523 (12.0%) versus 7561 dead/73,721 (10.3%); 46 trials, RR 1.03, 95% CI 1.00 to 1.05) significantly increased mortality, whereas vitamin A (3444 dead/24,596 (14.0%) versus 2249 dead/16,548 (13.6%); 12 trials, RR 1.07, 95% CI 0.97 to 1.18), vitamin C (3637 dead/36,659 (9.9%) versus 2717 dead/29,283 (9.3%); 29 trials, RR 1.02, 95% CI 0.98 to 1.07), and selenium (2670 dead/39,779 (6.7%) versus 1468 dead/22,961 (6.4%); 17 trials, RR 0.97, 95% CI 0.91 to 1.03) did not significantly affect mortality. In univariate meta-regression analysis, the dose of vitamin A was significantly associated with increased mortality (RR 1.0006, 95% CI 1.0002 to 1.001, P = 0.002).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.

Hypothesis: hyperhomocysteinemia is an indicator of oxidant stress

Elevated plasma homocysteine levels are associated with an increased risk of atherosclerosis and thrombosis, as well as a variety of other pathologies such as birth defects, Alzheimer's disease and other dementias, osteoporosis, diabetes and renal disease. Homocysteine metabolism is catalyzed by a number of enzymes that require B-vitamins as cofactors, and homocysteine levels are particularly responsive to folate status. The predictive power of plasma homocysteine level as a risk factor for atherothrombotic orders raised the appealing hypothesis that reduction of homocysteine levels by vitamin supplementation might result in a commensurate reduction is the risk of atherothrombotic events. Unfortunately, most clinical trials failed to show a significant benefit of vitamin supplementation on cardiovascular events, in spite of significant lowering of plasma homocysteine levels. Thus, it is not clear whether homocysteine actually plays a causal role in many pathologies with which it is associated, or whether it is instead a marker for some other underlying mechanism. A large body of data links hyperhomocysteinemia and folate status with oxidant stress. In this article I review data that suggests that homocysteine not only promotes cellular and protein injury via oxidant mechanisms, but is also a marker for the presence of pathological oxidant stress. Thus, it is possible that hyperhomocysteinemia is not a common primary cause of atherothrombotic disorders in the general population, but rather a marker of systemic or endothelial oxidant stress that is a major mediator of these disorders.

Effect of folic acid supplementation on cardiovascular outcomes: a systematic review and meta-analysis

BACKGROUND

Folic acid is widely used to lower homocysteine concentrations and prevent adverse cardiovascular outcomes. However, the effect of folic acid on cardiovascular events is not clear at the present time. We carried out a comprehensive systematic review and meta-analysis to assess the effects of folic acid supplementation on cardiovascular outcomes.

METHODOLOGY AND PRINCIPAL FINDINGS

We systematically searched Medline, EmBase, the Cochrane Central Register of Controlled Trials, reference lists of articles, and proceedings of major meetings for relevant literature. We included randomized placebo-controlled trials that reported on the effects of folic acid on cardiovascular events compared to placebo. Of 1594 identified studies, we included 16 trials reporting data on 44841 patients. These studies reported 8238 major cardiovascular events, 2001 strokes, 2917 myocardial infarctions, and 6314 deaths. Folic acid supplementation as compared to placebo had no effect on major cardiovascular events (RR, 0.98; 95% CI, 0.93-1.04), stroke (RR, 0.89; 95% CI,0.78-1.01), myocardial infarction (RR, 1.00; 95% CI, 0.93-1.07), or deaths from any cause (RR, 1.00;95% CI, 0.96-1.05). Moreover, folic acid as compared to placebo also had no effect on the following secondary outcomes: risk of revascularization (RR, 1.05; 95%CI, 0.95-1.16), acute coronary syndrome (RR, 1.06; 95%CI, 0.97-1.15), cancer (RR, 1.08; 95%CI, 0.98-1.21), vascular death (RR, 0.94; 95%CI,0.88-1.02), or non-vascular death (RR, 1.06; 95%CI, 0.97-1.15).

CONCLUSION/SIGNIFICANCE

Folic acid supplementation does not effect on the incidence of major cardiovascular events, stroke, myocardial infarction or all cause mortality.

The prevalence and trends of overweight, obesity and nutrition-related non-communicable diseases in the Arabian Gulf States

This paper reviews studies on the prevalence of overweight, obesity and related nutrition-related non-communicable diseases in Bahrain, Kuwait, Qatar, Oman, Saudi Arabia and the UAE. Obesity is common among women; while men have an equal or higher overweight prevalence. Among adults, overweight plus obesity rates are especially high in Kuwait, Qatar and Saudi Arabia, and especially among 30-60 year olds (70-85% among men; 75-88% among women), with lower levels among younger and elderly adults. The rate of increase in obesity was pronounced in Saudi Arabia and Kuwait. Prevalence of obesity is high among Kuwaiti and Saudi pre-schoolers (8-9%), while adolescent overweight and obesity are among the highest in the world, with Kuwait having the worst estimates (40-46%); however, comparison of child data is difficult because of differing standards. Among nutrition-related non-communicable diseases, hypertension and diabetes levels are very high and increase with age, with the UAE performing the worst because of a rapid rate of increase between 1995 and 2000. Additional monitoring of the prevalence of metabolic syndrome and cancers is necessary. Nationally representative longitudinal surveys with individual, household and community-level information are needed to determine the importance of various factors that contribute to these troubling trends.

Vitamin E and risk of cardiovascular diseases: a review of epidemiologic and clinical trial studies

Cardiovascular diseases are the leading cause of worldwide mortality. There is strong epidemiologic evidence for a beneficial effect of vitamin E on cardiovascular disease risk. However, conflicting results have been reported by intervention studies. To assess the potential benefit of vitamin E intake on the risk of cardiovascular diseases, fifty-nine published reports from observational studies, retrospective and prospective, randomised clinical trials, meta-analyses as well as pooling analyses were reviewed. The paper provides a detailed discussion about design, quality and limitations of these studies with regard to the evidence of the hypothesized relationship between vitamin E and cardiovascular diseases.

Efficacy of homocysteine-lowering therapy with folic Acid in stroke prevention: a meta-analysis

BACKGROUND AND PURPOSE

Although a lower serum homocysteine concentration is associated with a reduced risk of stroke in epidemiologic studies, randomized, controlled trials have yielded mixed findings regarding the effect of therapeutic homocysteine lowering on stroke prevention. We performed a meta-analysis of randomized, controlled trials to assess the efficacy of folic acid supplementation in the prevention of stroke.

METHODS

Salient trials were identified by formal literature search. Relative risk (RR) with 95% CI was used as a measure of the association between folic acid supplementation and risk of stroke, after pooling data across trials in a fixed-effects model.

RESULTS

The search identified 13 randomized, controlled trials that had enrolled 39 005 participants for folic acid therapy to reduce homocysteine in which stroke was reported as an outcome measure. Across all trials, folic acid supplementation was associated with a trend toward mild benefit that did not reach statistical significance in reducing the risk of stroke (RR=0.93; 95% CI, 0.85-1.03; P=0.16). The RR for nonsecondary prevention trials was 0.89 (95% CI, 0.79-0.99; P=0.03). In stratified analyses, a greater beneficial effect was seen in the trials testing combination therapy of folic acid plus vitamins B6 and B12 (RR=0.83; 95% CI, 0.71-0.97; P=0.02) and in the trials that disproportionately enrolled male patients (men:women >2; RR=0.84; 95% CI, 0.74-0.94; P=0.003).

CONCLUSIONS

Folic acid supplementation did not demonstrate a major effect in averting stroke. However, potential mild benefits in primary stroke prevention, especially when folate is combined with B vitamins and in male patients, merit further investigation.