Serum Vitamin D Levels in Relation to Hypertension and Pre-hypertension in Adults: A Systematic Review and Dose–Response Meta-Analysis of Epidemiologic Studies

Impact of vitamins A, D, and homocysteine on cardiometabolic multimorbidity in Northwest China

OBJECTIVE

To investigate the impact of vitamin A (VA), vitamin D (VD), and homocysteine (Hcy) on cardiometabolic multimorbidity (CMM).

METHODS

This study is a cross-sectional study conducted in Ningxia Province, China. A total of 5000 participants aged 25-74 were recruited and divided into two groups based on the definition of cardiometabolic multimorbidity: the CMM group and the Non CMM group. Demographic, lifestyle, and laboratory data were collected to investigate the correlation between vitamin A, D, Hcy levels and CMM risk. The association was analyzed using multiple logistic regression and restricted cubic spline method.

RESULTS

CMM incidence increased with age, being higher in females (20.05%) compared to males, Hypertension was present in 96.20% of CMM cases. Reduced VD levels correlated with an elevated CMM risk (OR = 1.799, 95% CI: 1.466-2.238), showing an inverse dose-response relationship, even after adjusting for confounders (OR = 1.553, 95% CI: 1.233-1.956). However, VA and Hcy levels were not significantly associated with CMM risk. The inverse correlation between VD status and CMM risk was more pronounced in males, obese individuals, and those with normal blood lipid profiles (P < 0.05).

CONCLUSIONS

The risk of CMM increases with age, especially in women. Inadequate VD status increases vulnerability to CMM, suggesting that optimising VD reduces the risk of CMM.

Serum vitamin D, blood pressure and hypertension risk in the HUNT study using observational and Mendelian randomization approaches

Limited studies have triangulated the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels and systolic blood pressure (SBP), diastolic blood pressure (DBP) or hypertension risk utilizing both observational and Mendelian randomization (MR) approaches. We employed data from the Norwegian Trøndelag Health Study (HUNT) to conduct cross-sectional (n = 5854) and prospective (n = 3592) analyses, as well as one-sample MR (n = 86,324). We also used largest publicly available data for two-sample MR. Our cross-sectional analyses showed a 25 nmol/L increase in 25(OH)D was associated with a 1.73 mmHg decrease in SBP (95% CI - 2.46 to - 1.01), a 0.91 mmHg decrease in DBP (95% CI - 1.35 to - 0.47) and 19% lower prevalence of hypertension (OR 0.81, 95% CI 0.74 to 0.90) after adjusting for important confounders. However, these associations disappeared in prospective analyses. One-sample and two-sample MR results further suggested no causal relationship between serum vitamin D levels and blood pressure or hypertension risk in the general population.

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.

Serum 25(OH)D Concentration, Vitamin D Supplementation, and Risk of Cardiovascular Disease and Mortality in Patients with Type 2 Diabetes or Prediabetes: a Systematic Review and Dose-Response Meta-Analysis

BACKGROUND

Evidence is uncertain about the association between serum 25-hydroxyvitamin D (25(OH)D) concentration and health outcomes in people with type 2 diabetes.

OBJECTIVES

We aimed to assess the association between vitamin D status and all-cause mortality and cardiovascular disease in people with type 2 diabetes.

METHODS

We did a systematic search in PubMed, Scopus, CENTRAL, and Web of Science until May 2022. We selected 1) cohort studies investigating the association between serum 25(OH)D concentration and mortality or cardiovascular disease in people with type 2 diabetes or prediabetes and 2) randomized trials of vitamin D supplementation in these patients. We used random-effects pairwise meta-analyses to calculate summary relative risks (RRs) and 95% confidence intervals (CI).

RESULTS

21 cohort studies and 6 randomized trials were included. Compared with sufficient vitamin D status (≥50 nmol/L), the RR of all-cause mortality was 1.36 (95% CI: 1.23, 1.49; n = 11 studies, GRADE = moderate) for vitamin D insufficiency (25 to <50 nmol/L), and 1.58 (1.33, 1.83; n = 16, GRADE = moderate) for deficiency (<25 nmol/L). Similar findings were observed for cardiovascular mortality and morbidity but not for cancer mortality. The certainty of evidence ranged from very low to moderate. Dose-response meta-analyses indicated nonlinear associations, with the lowest risk at 25(OH)D ∼60 nmol/L for all-cause and cardiovascular mortality. Supplementation with vitamin D did not reduce the risk of all-cause mortality (RR: 0.96, 95% CI: 0.79, 1.16; risk difference per 1000 patients: 3 fewer, 95% CI: 16 fewer, 12 more; n = 6 trials with 7316 participants; GRADE = low) or the risk of cardiovascular mortality and morbidity (very low- to low-certainty evidence).

CONCLUSIONS

Vitamin D deficiency and insufficiency are associated with a higher risk of all-cause and cardiovascular mortality in patients with type 2 diabetes or prediabetes. Vitamin D deficiency should be corrected in patients with type 2 diabetes to reach normal serum 25(OH)D concentrations, preferably 60 nmol/L.

SYSTEMATIC REVIEW REGISTRATION

This systemic review was registered at PROSPERO as CRD42022326429 (=https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=326429).

Mechanisms Suggesting a Relationship between Vitamin D and Erectile Dysfunction: An Overview

Vitamin D deficiency (VDD) and erectile dysfunction (ED) heavily burden the male population. The higher prevalence of both conditions in the elderly suggests a possible relationship between the two conditions. In addition, in vitro, animal, and human studies have revealed several mechanisms that may relate VDD to ED. The main mechanism by which vitamin D might exert its action on sexual function appears to be through the regulation of endothelial function. Indeed, VDD correlates with several markers of endothelial function. The action of vitamin D on the endothelium would be exercised both indirectly through its intervention in inflammatory processes and through the production of oxygen free radicals, and directly through the regulation of vascular stiffness, the production of nitric oxide, and the regulation of vessel permeability. Furthermore, the ubiquitous distribution of the vitamin D receptor in the human body means that this hormone can also exert a beneficial effect on erectile function by interfering with those comorbidities significantly associated with ED, such as hypertension, diabetes mellitus, hypercholesterolemia, chronic kidney disease, and hypogonadism. In this review, we thoroughly and carefully presented the evidence and mechanisms that would appear to relate vitamin D levels to erectile function. Furthermore, we have summarized the meta-analytic evidence for and against this association to provide a true representation of this topic. Data published to date suggest that low levels of vitamin D could contribute to worsening erectile function through several mechanisms. Therefore, vitamin D levels should be measured in patients with ED and maintained at adequate levels by specific supplementation in case of deficiency. However, the low quality and heterogeneity of clinical trials evaluating the effects of vitamin D administration on erectile function and ED-associated comorbidities do not allow for a univocal conclusion, and indicate the need for further studies to analyze these aspects.

Low serum 25-hydroxyvitamin D levels are associated with increased cardiovascular morbidity and mortality

BACKGROUND

There is controversy about the association between vitamin D and cardiovascular disease (CVD). This article aims to explore the association of serum 25-hydroxyvitaminD (25 OHD) with the risk of CVD.

METHODS

PubMed, EMBASE, Web of Science database, OVID, and Cochrane Library databases (last updated in August 2022) were systematically searched. The relationship between 25OHD and the risk of CVD was assessed by using the 95% confidence intervals (CI) and hazard ratio (HR). The effect model was selected by the size of heterogeneity.

RESULTS

The meta-analysis included 40 cohort studies that contained 652352 samples. The pooled results showed that a decreased level of 25OHD was associated with an increased relative risk of total CVD events (HR = 1.35, 95% CI: 1.26-1.43). Furthermore, the results also showed that a decreased circulating 25OHD level was associated with an increased mortality of CVD (HR = 1.43, 95% CI: 1.30-1.57) and incidence of CVD (HR = 1.26, 95% CI: 1.16-1.36), especially an increased risk of heart failure (HF) (HR = 1.38, 95% CI: 1.2-1.6), myocardial infarction (MI) (HR = 1.28, 95% CI: 1.13-1.44) and coronary heart disease (CHD) (HR = 1.28, 95% CI: 1.1-1.49).

CONCLUSIONS

The current meta-analysis shows that reduced serum 25OHD concentrations is not only associated with increased total cardiovascular events and cardiovascular mortality, but also with increased risk of HF, MI, and CHD.

LIMITATIONS

The underlying mechanism still needs to be explored further, and well-designed RCTs are needed to confirm the role of vitamin D in the occurrence and development of CVD.

Latest Knowledge on the Role of Vitamin D in Hypertension

Hypertension is the third leading cause of the global disease burden, and while populations live longer, adopt more sedentary lifestyles, and become less economically concerned, the prevalence of hypertension is expected to increase. Pathologically elevated blood pressure (BP) is the strongest risk factor for cardiovascular disease (CVD) and related disability, thus making it imperative to treat this disease. Effective standard pharmacological treatments, i.e., diuretics, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blocker (ARBs), beta-adrenergic receptor blockers (BARBs), and calcium channel blockers (CCBs), are available. Vitamin D (vitD) is known best for its role in bone and mineral homeostasis. Studies with vitamin D receptor (VDR) knockout mice show an increased renin-angiotensin-aldosterone system (RAAS) activity and increased hypertension, suggesting a key role for vitD as a potential antihypertensive agent. Similar studies in humans displayed ambiguous and mixed results. No direct antihypertensive effect was shown, nor a significant impact on the human RAAS. Interestingly, human studies supplementing vitD with other antihypertensive agents reported more promising results. VitD is considered a safe supplement, proposing its great potential as antihypertensive supplement. The aim of this review is to examine the current knowledge about vitD and its role in the treatment of hypertension.

Associations among vitamin D, tobacco smoke, and hypertension: A cross-sectional study of the NHANES 2001-2016

The interrelationships among vitamin D, tobacco smoking, and hypertension are currently unknown. This study was conducted to determine the relationship between vitamin D levels and hypertension and the effect of tobacco smoke exposure levels on this relationship among US adults. We performed a cross-sectional analysis of adult participants from the 2001-2016 National Health and Nutrition Examination Survey (NHANES). Serum 25-hydroxyvitamin D concentration was used as a biomarker of vitamin D status, and tobacco smoke exposure levels were objectively evaluated by serum cotinine levels. Among 22,875 eligible adults who were not receiving antihypertensive medications, the prevalence of hypertension, vitamin D deficiency (<50 mmol/L), and cotinine ≥3 ng/mL was 13.9%, 34.9%, and 29.4%, respectively. Serum cotinine and vitamin D levels were independently associated with hypertension risk after controlling for confounders (P < 0.05). When stratified by the cotinine group (<0.05, 0.05-3 and ≥3 ng/mL), we found that the risk of hypertension associated with vitamin D deficiency was higher among subjects with cotinine levels ≥3 ng/mL compared with the other strata [OR (95% CI) 1.30 (1.09, 1.54) vs. 1.53 (1.19, 1.96) vs. 1.64 (1.30, 2.06); P for heterogeneity test <0.05]. Furthermore, serum cotinine levels were negatively correlated with vitamin D levels. These findings suggested that the increased risk of hypertension could be partly attributed to low vitamin D levels induced by tobacco smoke exposure, in addition to the effects of tobacco smoke exposure and vitamin D deficiency themselves.

Inverse association of serum carotenoid levels with prevalence of hypertension in the general adult population

Carotenoid levels are inversely associated with blood pressure (BP). This study focused on the effects of individual and combined serum carotenoids on BP and hypertension, which have not been established to date. Data from National Health and Nutrition Examination Survey (NHANES) 2001–2006 were analyzed in this cross-sectional study. Multivariate logistic, linear, and weighted quantile sum (WQS) regression analyses were applied to explore the associations of six serum carotenoids (α-carotene, β-cryptoxanthin, lutein/zeaxanthin, trans-lycopene, trans-β-carotene, and cis-β-carotene), individually and in combination, with BP/hypertension. The linearity of correlations was further assessed using restricted cubic spline (RCS) regression. A total of 11,336 adults were included for analysis. Data from multivariate models showed that all six carotenoids were independently and negatively associated with both systolic blood pressure (SBP) and diastolic blood pressure (DBP; all p < 0.05). Compared to the first quartile, the fourth quartile of α-carotene (odds ratio [OR] = 0.64 [0.52–0.77]), β-cryptoxanthin (OR = 0.74 [0.60–0.90]), trans-β-carotene (OR = 0.50 [0.40–0.61]), and cis-β-carotene (OR = 0.47 [0.35–0.64]) were significantly and inversely related to hypertension (all p < 0.05). Moreover, WQS analysis revealed that the combination of all six serum carotenoids was negatively associated with BP and hypertension (all P<0.001), among which trans-β-carotene was the most significant contributor to the protective effect against hypertension (weight, 59.50%). Dose-response analyses demonstrated a linear inverse association of all carotenoids with hypertension (p for non-linearity > 0.05). Our collective findings indicate that higher levels of all six mixed serum carotenoids are correlated with decreased prevalence of hypertension, among which β-carotene exerts the most significant effect, which may provide a basis and direction for further studies.

Comparing the Evidence from Observational Studies and Randomized Controlled Trials for Nonskeletal Health Effects of Vitamin D

Although observational studies of health outcomes generally suggest beneficial effects with, or following, higher serum 25-hydroxyvitamin D [25(OH)D] concentrations, randomized controlled trials (RCTs) have generally not supported those findings. Here we review results from observational studies and RCTs regarding how vitamin D status affects several nonskeletal health outcomes, including Alzheimer's disease and dementia, autoimmune diseases, cancers, cardiovascular disease, COVID-19, major depressive disorder, type 2 diabetes, arterial hypertension, all-cause mortality, respiratory tract infections, and pregnancy outcomes. We also consider relevant findings from ecological, Mendelian randomization, and mechanistic studies. Although clear discrepancies exist between findings of observational studies and RCTs on vitamin D and human health benefits these findings should be interpreted cautiously. Bias and confounding are seen in observational studies and vitamin D RCTs have several limitations, largely due to being designed like RCTs of therapeutic drugs, thereby neglecting vitamin D's being a nutrient with a unique metabolism that requires specific consideration in trial design. Thus, RCTs of vitamin D can fail for several reasons: few participants' having low baseline 25(OH)D concentrations, relatively small vitamin D doses, participants' having other sources of vitamin D, and results being analyzed without consideration of achieved 25(OH)D concentrations. Vitamin D status and its relevance for health outcomes can usefully be examined using Hill's criteria for causality in a biological system from results of observational and other types of studies before further RCTs are considered and those findings would be useful in developing medical and public health policy, as they were for nonsmoking policies. A promising approach for future RCT design is adjustable vitamin D supplementation based on interval serum 25(OH)D concentrations to achieve target 25(OH)D levels suggested by findings from observational studies.