Confirmed hypertension and plasma 25(OH)D concentrations amongst elderly men

Vitamin D Deficiency Association with Comorbid Diseases in Palestine: "A Cross-Sectional Observation Study"

BACKGROUND

Vitamin D deficiency (VDD) is a global health concern. This study aimed to determine the prevalence of vitamin D deficiency and its associated comorbidities in Palestine, such as diabetes mellitus, hypertension, hyperlipidemia, and cardiovascular and autoimmune diseases.

METHODS

A retrospective, descriptive study retrieved medical data from the Nat Health insurance processor database from 2014 to 2020. Patient information included age, sex, vitamin D laboratory order, symptoms, and comorbidities. This study included patients prescribed vitamin D at a dose of 50000IU for vitamin D deficiency confirmed by a serum vitamin D laboratory test. The collected data were analyzed using IBM SPSS. In addition, a chi-square test was conducted to assess the association between vitamin D deficiency, symptoms, and comorbidities.

RESULTS

Data of 3011 patients were collected; 639 patients were diagnosed with osteoporosis, and 39 patients prescribed vitamin D without a laboratory test were excluded. Approximately, 1837 (78%) participants had vitamin D deficiency. A total of 1330 women (81.3%) were significantly more likely to have vitamin D deficiency than males, 507 (72.7%; P < 0.001). Joint pain, back pain, and cervicalgia were significantly associated with vitamin D deficiency (P < 0.001). Asymptomatic participants (2.1%) were significantly less likely to have vitamin D deficiency than symptomatic participants (9.5%, p < 0.001). Hypothyroidism is significantly associated with vitamin D deficiency (p = 0.048).

CONCLUSION

In this retrospective study, the prevalence of vitamin D was high and alarming. There was a significant association between VDD, patients who presented with back pain, arthritis, and cervicalgia symptoms, and patients diagnosed with hypothyroidism. Therefore, health initiative programs are warranted to increase awareness regarding screening, prevention, and treatment. Further studies are needed to confirm the relationship between vitamin D supplementation and the reduced risk of comorbid diseases.

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

Background

Findings of observational studies that evaluated the association of serum vitamin D status and high blood pressure were contradictory. This meta-analysis of epidemiologic studies assessed the relation of serum vitamin D levels to hypertension (HTN) and pre-hypertension in adults.

Methods

We conducted a systematic search of all published articles up to March 2021, in four electronic databases (MEDLINE (PubMed), Web of Science (ISI), Embase and Scopus), and Google scholar. Seventy epidemiologic studies (10 prospective cohort, one nested case–control, and 59 cross-sectional investigations) that reported relative risks (RRs), odds ratios (ORs), hazard ratios, or prevalence ratios with 95% CIs for HTN or pre-hypertension in relation to serum vitamin D concentrations in adults were included in the analysis.

Results

In prospective studies, a 16% decrease in risk of hypertension was observed in participants with high levels of serum vitamin D compared to low levels (RR: 0.84; 95%CI: 0.73, 0.96; 12 effect sizes). Dose–response analysis in prospective studies revealed that each 25 nmol/L increase in serum vitamin D concentrations resulted in 5% reduced risk of HTN (RR: 0.95; 95% CI: 0.90, 1.00). Also, a significant nonlinear relationship between serum vitamin D levels and HTN was found (P_nonlinearity < 0.001). In cross-sectional investigations, highest vs. lowest level of serum vitamin D was related to reduced odds of HTN (OR: 0.84; 95%CI: 0.79, 0.90; 66 effect sizes) and pre-hypertension (OR: 0.75; 0.95%CI: 0.68, 0.83; 9 effect sizes). Dose–response analysis in these studies showed that each 25 nmol/L increase in serum vitamin D levels was related to a significant 6% reduction in odds of hypertension in all populations (RR: 0.94; 95%CI: 0.90, 0.99) and 3% in studies with representative populations (RR: 0.97; 95%CI: 0.95, 0.99).

Conclusion

This meta-analysis of epidemiologic studies disclosed that serum vitamin D concentrations were inversely related to the risk of HTN in adults, in a dose–response manner in both prospective cohort and cross-sectional studies.

Systematic Review Registration:http://www.crd.york.ac.uk/Prospero, identifier: CRD42021251513.

The effects of vitamin D and curcuminoids supplementation on anthropometric measurements and blood pressure in type 2 diabetic patients with coexisting hypovitaminosis D: A double-blind, placebo-controlled randomized clinical trial

BACKGROUND AND AIMS

Curcuminoids and vitamin D have been shown to improve blood pressure and body weight in diabetic animals; however, consistent findings in type 2 diabetes mellitus (T2DM) patients are limited. This study was performed to evaluate the effects of curcuminoids and vitamin D, simultaneously or singly on anthropometric measurements and blood pressure in T2DM patients with insufficient vitamin D level.

METHODS

In this randomized, placebo-controlled clinical trial, eighty T2DM patients were randomly assigned into 4 groups receiving (1) 500 mg/day curcuminoids; (2) 50,000 IU/week vitamin D₃; (3) 50,000 IU/week vitamin D₃ plus 500 mg/d curcuminoids; or (4) placebos for 12 weeks. Blood pressure and anthropometric measurements were evaluated before and after intervention.

RESULTS

Intergroup comparisons showed that Vitamin D (main effect) significantly reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP) (P = 0/000). Curcuminoids (main effect) significantly reduced DBP (P = 0/001). Interaction effects showed that curcuminoids significantly prevented the effect of vitamin D on the reduction of SBP (P = 0.006). Whereas, vitamin D and curcuminoids had a synergistic effect on DBP reduction (P = 0.006). The comparison of changes in anthropometric measurements between the four groups showed no significant differences in the raw and adjusted models. In-group comparisons showed that SBP, DBP, waist to hip circumference (WHR), body fat mass (BFM), percent body fat (PBF) and visceral fat area (VFA) values were significantly reduced in all groups except the placebo group compared to baseline values. Only in the CR-D group, there was a significant reduction in body weight (P = 0/047).

CONCLUSIONS

Curcuminoids and vitamin D may have beneficial effects on blood pressure and anthropometric measurements in T2DM patients. CLINICAL REGISTRATION: http://www.IRCT.ir:IRCT2017041213678N22.

Prevalence of vitamin D deficiency and associated comorbidities among Abu Dhabi Emirates population

OBJECTIVE

The study explored the prevalence of vitamin D deficiency, its seasonal variation and associated comorbidities among the Abu Dhabi Emirati population living in urban and suburban settings.

RESULT

Of the 12,346 participants 36.9% were male and 63.1% female. The majority (72%) were either vitamin D deficient (< 50 nmol/L), or (10%) vitamin D insufficient (50-74 nmol/L). Vitamin D deficiency was similar in both sexes (male 83.1% vs female 83.8%) as insufficiency (male 12.7% vs female 11.2%). Low vitamin D levels were associated with high blood pressure, high body mass index, central obesity, high cholesterol, impaired blood glucose levels and a high Framingham risk score. The mean vitamin D level was highest in January (winter) and lowest in July (summer).

Vitamin D deficiency and risk of cardiovascular diseases: a narrative review

Vitamin D, a fat-soluble prohormone, has wide-ranging roles in the regulation of many physiological processes through their interactions with the vitamin D receptors (VDR). It plays a major role in bones and calcium metabolism. Vitamin D deficiency is not uncommon and it has been associated with many health-related issues, including skeletal and non-skeletal complications. The association of low vitamin D and cardiovascular diseases and risk factors has been explored in both animal and human studies. However, studies and trials on the effect of vitamin D supplementation on cardiovascular risk factors and hypertension are conflicting with inconsistent results. Therefore, large, well-powered randomized controlled trials are warranted. If successful, supplementation with easy and low-cost vitamin D can impact our health positively. Here, we summarized the evidence for the association of vitamin D, cardiovascular diseases and risk factors, including coronary artery diseases, stroke, and hypertension, and mortality, with special consideration to resistant hypertension.

Vitamin D and cardiovascular diseases: Causality

Vitamin D regulates blood pressure, cardiac functions, and endothelial and smooth muscle cell functions, thus, playing an important role in cardiovascular health. Observational studies report associations between vitamin D deficiency with hypertension and cardiovascular-related deaths. Peer-reviewed papers were examined in several research databases as per the guidelines of the Preferred Reporting Items for Systematic Reviews, using key words that address the relationship between vitamin D and cardiovascular disease. Correlations and interpretations were made considering the risks-benefits, broader evidence, and implications. This review analyzed current knowledge regarding the effects of vitamin D on the cardiovascular system. 1,25(OH)₂D and related epigenetic modifications subdue cellular inflammation, improve overall endothelial functions, reduce age-related systolic hypertension and vascular rigidity, and attenuate the actions of the renin-angiotensin-aldosterone system. Most observational and ecological studies support 25(OH)vitamin D having protective effects on the cardiovascular system. However, the association of vitamin D deficiency with cardiovascular diseases is based primarily on observational and ecological studies and thus, is a matter of controversy. Adequately powered, randomized controlled clinical trial data are not available to confirm these associations. Thus, to test the hypothesis that correction of vitamin D deficiency protects the cardiovascular system, well-designed, statistically powered, longer-term clinical trials are needed in persons with vitamin D deficiency. Nevertheless, the available data support that adequate vitamin D supplementation and/or sensible sunlight exposure to achieve optimal vitamin D status are important in the prevention of cardiovascular disease and other chronic diseases.

Implications of the nutrition transition for vitamin D intake and status in Aboriginal groups in the Canadian Arctic

Aboriginal Canadians have low intakes of vitamin D and are shifting away from consumption of traditional foods. Higher body mass index, skin pigmentation, and geographic latitude of residence further predispose Canadian Aboriginal populations to low vitamin D status. Low vitamin D status could compromise bone health and other health outcomes. Studies assessing vitamin D status of different Aboriginal groups are limited. The aim of this review is to examine the literature on vitamin D status and intakes of Canadian Aboriginal populations living in the Arctic. PubMed was searched for relevant articles published from 1983 to 2013. The prevalence of 25-hydroxy vitamin D deficiency ranged from 13.9% to 76.0% among children and adults in the summer. Furthermore, mean vitamin D intakes among all age groups were below the estimated average requirement. As vitamin D deficiency has been recently associated with chronic diseases, and Aboriginal populations living in the Arctic are at high risk for low vitamin D status, their vitamin D status should be assessed regularly across seasons.

Vitamin D supplementation for the prevention of type 2 diabetes in overweight adults: study protocol for a randomized controlled trial

Background

Despite Australia’s sunny climate, low vitamin D levels are increasingly prevalent. Sun exposure is limited by long working hours, an increase in time spent indoors, and sun protection practices, and there is limited dietary vitamin D fortification. While the importance of vitamin D for bone mineralization is well known, its role as a protective agent against chronic diseases, such as type 2 diabetes and cardiovascular disease, is less understood. Observational and limited intervention studies suggest that vitamin D might improve insulin sensitivity and secretion, mainly via its anti-inflammatory properties, thereby decreasing the risk of development and progression of type 2 diabetes. The primary aim of this trial is to investigate whether improved plasma concentrations of 25-hydroxyvitamin D (25(OH)D), obtained through vitamin D supplementation, will increase insulin sensitivity and insulin secretion. A secondary aim is to determine whether these relationships are mediated by a reduction in underlying subclinical inflammation associated with obesity.

Methods/Design

Fifty overweight but otherwise healthy nondiabetic adults between 18 and 60 years old, with low vitamin D levels (25(OH)D < 50 nmol/l), will be randomly assigned to intervention or placebo. At baseline, participants will undergo a medical review and anthropometric measurements, including dual X-ray absorptiometry, an intravenous glucose tolerance test, muscle and fat biopsies, a hyperinsulinemic euglycemic clamp, and questionnaires assessing diet, physical activity, sun exposure, back and knee pain, and depression. The intervention group will receive a first dose of 100,000 IU followed by 4,000 IU vitamin D (cholecalciferol) daily, while the placebo group will receive apparently identical capsules, both for a period of 16 weeks. All measurements will be repeated at follow-up, with the primary outcome measure expressed as a change from baseline in insulin sensitivity and secretion for the intervention group compared with the placebo group. Secondary outcome measures will compare changes in anthropometry, cardiovascular risk factors, and inflammatory markers.

Discussion

The trial will provide much needed clinical evidence on the impact of vitamin D supplementation on insulin resistance and secretion and its underlying mechanisms, which are relevant for the prevention and management of type 2 diabetes.

Trial registration

Clinicaltrials.gov ID: NCT02112721.

Vitamin D status and hypertension: a review

Vitamin D is a steroid prohormone synthesized in the skin following ultraviolet exposure and also achieved through supplemental or dietary intake. While there is strong evidence for its role in maintaining bone and muscle health, there has been recent debate regarding the role of vitamin D deficiency in hypertension based on conflicting epidemiological evidence. Thus, we conducted a scoping systematic literature review and meta-analysis of all observational studies published up to early 2014 in order to map trends in the evidence of this association. Mixed-effect meta-analysis was performed to pool risk estimates from ten prospective studies (n=58,262) (pooled risk for incident hypertension, relative risk [RR] =0.76 (0.63–0.90) for top vs bottom category of 25-hydroxyvitamin D [25OHD]) and from 19 cross-sectional studies (n=90,535) (odds ratio [OR] =0.79 (0.73–0.87)). Findings suggest that the better the assessed quality of the respective study design, the stronger the relationship between higher 25OHD levels and hypertension risk (RR =0.67 (0.51–0.88); OR =0.77 (0.72–0.89)). There was significant heterogeneity among the findings for both prospective and cross-sectional studies, but no evidence of publication bias was shown. There was no increased risk of hypertension when the participants were of older age or when they were vitamin D deficient. Younger females showed strong associations between high 25OHD levels and hypertension risk, especially in prospective studies (RR =0.36 (0.18–0.72); OR =0.62 (0.44–0.87)). Despite the accumulating evidence of a consistent link between vitamin D and blood pressure, these data are observational, so questions still remain in relation to the causality of this relationship. Further studies either combining existing raw data from available cohort studies or conducting further Mendelian analyses are needed to determine whether this represents a causal association. Large randomized controlled trials are also needed to determine whether vitamin supplementation may be beneficial in the prevention or the treatment of hypertension.

Potential pathophysiological role for the vitamin D deficiency in essential hypertension

Vitamin D deficiency has been indicated as a pandemic emerging public health problem. In addition to the well-known role on calcium-phosphorus homeostasis in the bone, vitamin D-mediated processes have been recently investigated on other diseases, such as infections, cancer and cardiovascular diseases. Recently, both the discovery of paracrine actions of vitamin D (recognized as “local vitamin D system”) and the link of vitamin D with renin-angiotensin-aldosterone system and the fibroblast growth factor 23/klotho pathways highlighted its active cardiovascular activity. Focusing on hypertension, this review summarizes the more recent experimental evidence involving the vitamin D system and deficiency in the cardiovascular pathophysiology. In particular, we updated the vascular synthesis/catabolism of vitamin D and its complex interactions between the various endocrine networks involved in the regulation of blood pressure in humans. On the other hand, the conflicting results emerged from the comparison between observational and interventional studies emphasize the fragmentary nature of our knowledge in the field of vitamin D and hypertension, strongly suggesting the need of further researches in this field.

Vitamin D: new implications for mood and blood pressure

This article reviews the 2011 guidelines for the evaluation, treatment, and prevention of vitamin D deficiency as well as the research literature evidencing an association between vitamin D, blood pressure and depression. Studies reveal an association between vitamin D levels and both systolic blood pressure and depression.

Does vitamin D modulate blood pressure?

PURPOSE OF REVIEW

Both vitamin D deficiency and hypertension are highly prevalent. It is unclear whether vitamin D modulates blood pressure and therefore whether vitamin D testing and therapy should become part of routine hypertension prevention and management. This article provides an overview of the data, with special emphasis on the work published in the last 2 years.

RECENT FINDINGS

Several animal studies corroborate the strong effect of vitamin D on the renin-angiotensin-aldosterone axis. Small and large observational studies have found associations between vitamin D, increased blood pressure, and the risk of developing hypertension. In contrast, recent data from randomized trials are mixed. Two randomized trials with approximately 1 year of follow-up detected no association between vitamin D treatment and blood pressure, whereas another study of active vitamin D reported a 9-mmHg decrease in systolic blood pressure. Meta-analyses have linked vitamin D levels with blood pressure, but the effect of vitamin D administration on blood pressure remains controversial.

SUMMARY

Vitamin D deficiency is asociated with high blood pressure in observational studies. This effect is thought to be partly mediated through regulation of the renin-angiotensin-aldosterone axis. However, randomized clinical trials and their meta-analyses have yielded inconclusive results. Large randomized trials focusing on patients with severe vitamin D deficiency and hypertension are needed before vitamin D can be recommended for the prevention or treatment of hypertension.

Relationship between 25-hydroxyvitamin D and all-cause and cardiovascular disease mortality

BACKGROUND

Observational studies have suggested a strong relationship between 25(OH)D and all-cause and cardiovascular disease mortality. A few studies also have described a nonlinear trend for this relationship in population subgroups, but less is known about this relationship in healthy adults. We examined the presence of a nonlinear relationship between 25(OH)D and all-cause and cardiovascular disease mortality among healthy adults.

METHODS

We examined 10,170 participants (≥18 years of age) using National Health and Nutrition Examination Survey data (2001-2004) combined with National Death Index for vital status information through December 2006. Cox proportional hazard models with spline (single knot at population median of 25[OH]D) were fit to estimate hazard ratios (HRs) for all-cause and cardiovascular disease mortality for each 10-unit increase in serum 25(OH)D. Models were adjusted for demographic and conventional cardiovascular disease risk factors.

RESULTS

Mean age of study participants was 46.6 (20.5) years, while median (interquartile range) 25(OH)D was 21 (15-27) ng/mL. After a median follow-up of 3.8 years (range 2.8-4.9), 509 all-cause and 184 cardiovascular diseases-related deaths were observed. In univariate analysis, 25(OH)D decreased hazards of all-cause (HR 0.59; 95% confidence interval [CI], 0.45-0.77) and cardiovascular disease (HR 0.56; 95% CI, 0.38-0.82) mortality below but not above its population median. In adjusted models, 25(OH)D retained the inverse association for all-cause (HR 0.54; 95% CI, 0.35-0.84) and cardiovascular disease (HR 0.50; 95% CI, 0.26-0.98) mortality below but not above its population median.

CONCLUSIONS

We found an inverse association between 25(OH)D and all-cause and cardiovascular disease mortality in healthy adults with serum 25(OH)D levels of ≤21 ng/mL. Clinical trials for the primary prevention of cardiovascular disease with 25(OH)D supplementation may target healthy adults with serum 25(OH)D levels of ≤21 ng/mL to validate these findings.

Vitamin D and hypertension: an update and review

PURPOSE OF REVIEW

Vitamin D deficiency and hypertension are highly prevalent. This review will discuss the association between vitamin D deficiency and blood pressure.

RECENT FINDINGS

During the past several years multiple prospective cohorts and randomized studies have been published. Recent studies have focused mostly on 25-hydroxy vitamin D, but a small number of trials used active vitamin D analog compounds.

SUMMARY

Data from cross-sectional studies report that low 25-hydroxy vitamin D is associated with higher systolic blood pressure and higher incidence of hypertension. Large observational studies show a weaker, yet similar association, but they have not largely accounted for the change in vitamin D levels over time. Randomized control trials conflict with observational data probably due to differences in populations studied, doses of vitamin D used, and unmeasured confounders. Further research is needed before clinical practice recommends vitamin D prescription as treatment for hypertension in the general population.

Arterial structure and function in mild primary hyperparathyroidism is not directly related to parathyroid hormone, calcium, or vitamin D

Objective

Elevated levels of calcium and parathyroid hormone (PTH), characteristics of primary hyperparathyroidism (PHPT), may be associated with cardiovascular morbidity and mortality in the general population. We evaluated the possible vascular effects of these risk factors in patients with mild PHPT by using standard methods and new imaging techniques.

Design

A prospective case-control study.

Subjects and Methods

Forty-eight patients with mild PHPT without any known cardiovascular risk factors were studied at baseline and at one year after parathyroidectomy (PTX) in comparison with 48 healthy age- and gender-matched controls. We measured biochemical variables, augmentation index (AIx), aortic pulse wave velocity (PWV_ao), radial (IMT_rad) and common carotid artery (IMT_cca) intima media thicknesses, and the grayscale median (IM-GSM) of the latter.

Results

No significant differences were observed between PHPT patients and controls at baseline for AIx (28.6±12.2 vs. 27.7±12.8%), IMT_rad (0.271±0.060 vs. 0.255±0.053 mm), IMT_cca (0.688±0.113 vs. 0.680±0.135 mm), or IM-GSM (82.3±17.2 vs. 86.5±15.3), while PWV_ao was slightly higher in patients (8.68±1.50 vs. 8.13±1.55, p<0.05). Systolic blood pressure (SBP), calcium, and PTH were higher in patients compared with controls, and decreased after PTX, while vitamin D was lower in patients and increased after PTX. While AIx, PWV_ao, IMT_rad, and IMT_cca were related to SBP, neither correlated to vitamin D levels. Only PWV_ao correlated weakly to plasma PTH (r = 0.29, p<0.01) and ionized calcium (r = 0.22, p<0.05) but showed no relation when age and SBP were adjusted for.

Conclusion

We found normal arterial function despite high calcium, PTH, and low vitamin D levels, in patients with mild PHPT without cardiovascular risk factors. The cardiovascular risk associated with low vitamin D and/or high PTH and calcium levels may be explained by their coupling to blood pressure and other risk factors rather than direct effects on arterial structure.

Vitamin D and vascular disease: the current and future status of vitamin D therapy in hypertension and kidney disease

Over the past decade, vitamin D has generated considerable interest as potentially having important effects on the vasculature and the kidney. Animal and human data indicate that vitamin D suppresses the activity of the renin-angiotensin system and improves endothelial function. Observational studies in humans suggest that low 25-hydroxyvitamin D (25[OH]D) levels are associated with a higher risk of hypertension. However, findings from randomized trials of vitamin D supplementation (with cholecalciferol or ergocalciferol) to lower blood pressure are inconsistent, possibly stemming from variability in study population, sample size, vitamin D dose, and duration. Supplementation with activated vitamin D (i.e., 1,25-dihydroxyvitamin D or analogues) in patients with chronic kidney disease reduces urine albumin excretion, an important biomarker for future decline in renal function. These studies are reviewed, with special emphasis on recent findings. Definitive studies are warranted to elucidate the effects of vitamin D supplementation on mechanisms of hypertension and kidney disease.

Association of serum 25-hydroxyvitamin D levels with markers for metabolic syndrome in the elderly: a repeated measure analysis

The purpose of current study was to investigate associations of serum 25-hydroxyvitamin D (OHVD) levels with markers for metabolic syndrome in elderly Koreans. We conducted a panel study on 301 individuals over 60 yr old in Seoul, Korea, and repeatedly measured serum OHVD, glucose, insulin, and lipid levels. Mixed effect model and generalized estimating equations were used to investigate relationships between serum OHVD levels with marker levels for metabolic syndrome and each of its categories. Of all subjects, 76.6% were vitamin D deficient (< 50 nM) and 16.9% were insufficient (< 75 nM). Inverse association was demonstrated between serum OHVD levels and insulin (P = 0.004), triglyceride (P = 0.023) and blood pressure (systolic blood pressure: P = 0.002; diastolic blood pressure: P < 0.001). Vitamin D deficiency was found to increase risk of 'hypertriglyceridemia' category of metabolic syndrome (odds ratio: 1.73, 95% confidence interval: 1.13-2.66). In conclusion, we found from our repeated measure analysis that decreasing serum OHVD levels are associated with increasing insulin resistance, increasing serum triglyceride levels and increasing blood pressure in elderly Koreans, and confirmed on the risk of 'hypertriglyceridemia' in vitamin D deficient subjects.

Modest reversal of metabolic syndrome manifestations with vitamin D status correction: a 12-month prospective study

Numerous cross-sectional studies have noted significant negative associations between circulating levels of 25-hydroxyvitamin D and cardiometabolic risk factors, highlighting potential extraskeletal functions of this sterol hormone. Prospective studies, however, have been limited; and hence, no cause-and-effect relations can be inferred. This study aims to determine whether vitamin D status correction can reverse already established manifestations of the metabolic syndrome (MetS). A total of 59 adult nondiabetic, overweight, and obese Saudis (31 male, 28 female) were prospectively enrolled in this 1-year interventional study. Anthropometry and biochemical evaluation were performed, including determination of serum 25-hydroxyvitamin D, calcium, and phosphorous concentrations, as well as fasting blood glucose and lipid profile. Subjects were advised to regularly expose themselves to sunlight and increase intake of vitamin D-rich foods. All measurements were repeated 6 and 12 months later. At the initial baseline visit, the prevalence of both low high-density lipoprotein cholesterol and hypertension was significantly increased among patients with 25-vitamin D deficiency (P < .05), even after adjusting for sex and body mass index. Overall prevalence of MetS patients by the modified National Health and Nutrition Examination Survey Adult Treatment Panel III definition decreased from 25.2% to 13.0%; and this was largely due to a parallel decrease in the prevalence of low high-density lipoprotein cholesterol, triglycerides, and hypertension. Optimization of vitamin D status through sun exposure and increased intake of a vitamin D-rich diet can lead to an improved cardiometabolic profile, offering a promising nonpharmacologic approach in the prevention of MetS manifestations.

The relationship between vitamin D and the renin-angiotensin system in the pathophysiology of hypertension, kidney disease, and diabetes

Vitamin D has been implicated in the pathophysiology of extraskeletal conditions such as hypertension, kidney disease, and diabetes via its ability to negatively regulate the renin-angiotensin system (RAS). This article reviews the evidence supporting a link between vitamin D and the RAS in these conditions, with specific emphasis on translational observations and their limitations. A literature review of animal and human studies evaluating the role of vitamin D in hypertension, kidney disease, and diabetes was performed. Excess activity of the RAS has been implicated in the pathogenesis of hypertension, chronic kidney disease, decreased insulin secretion, and insulin resistance. Animal studies provide strong support for 1,25-dihydroxyvitamin D(3)-mediated downregulation of renin expression and RAS activity via its interaction with the vitamin D receptor. Furthermore, the activity of vitamin D metabolites in animals is associated with reductions in blood pressure, proteinuria and renal injury, and with improved β-cell function. Many observational, and a few interventional, studies in humans have supported these findings; however, there is a lack of well-designed prospective human interventional studies to definitively assess clinical outcomes. There is a need for more well-designed prospective interventional studies to validate this hypothesis in human clinical outcomes.