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Vitamin D and cardiovascular disease: an appraisal of the evidence.

Coronary heart disease (CHD) [6] remains the leading cause of mortality in US men and women (1, 2). The primary risk factors for CHD in both sexes include older age, smoking, diabetes mellitus, dyslipidemia, hypertension, physical inactivity, obesity, the metabolic syndrome, a family history of premature CHD (males and females <55 and <65 years of age, respectively), and a personal history of peripheral arterial disease (2-5). Few Americans achieve optimal control of these risk factors, however, and these traditional risk factors do not explain many CHD events (6). Thus, novel approaches to reducing CHD risk remain of great interest.

Vitamin D has garnered recent attention for its potential cardioprotective properties and has become a topic of considerable interest in both the clinical and research communities. An increased incidence of CHD and hyperlipidemia in higher latitudes has been ecologically correlated with less sunlight (7). Other studies have reported that individuals with less exposure to ultraviolet light have lower vitamin D concentrations and a higher risk of CHD, myocardial infarction, and hypertension (8-10). Lower serum vitamin D concentrations have also been associated with increased risks of sudden cardiac death (11), peripheral arterial disease (12), and greater carotid intima-medial thickness (13). Randomized trials of these relationships have been sparse, however, and data related to these outcomes have been inconsistent. Postmenopausal women, as well as older men, may be at particularly high risk for vitamin D deficiency because of age-associated decreases in skin photoisomerization of 7-dehydrocholesterol (14) and lower dietary intakes of oral vitamin D.

Vitamin D Production and Homeostasis

Vitamin D (calciferol) is a term that refers to a group of lipid-soluble compounds with a 4-ringed cholesterol backbone. In the skin, pro-vitamin [D.sub.3] is photoisomerized to vitamin [D.sub.3] (cholecalciferol) by sunlight and ultraviolet light. The other major source of vitamin D is intestinal absorption. Vitamin [D.sub.3] is then transported to the liver, where it is hydroxylated to 25-hydroxyvitamin D (25OHD), which comprises both 25OH[D.sub.2] and 25OH[D.sub.3]. 25OHD then travels to the kidney, where it is further hydroxylated to 1,25-dihydroxyvitamin D [1,25[(OH).sub.2]D or calcitriol] (15), the physiologically active form of vitamin D (16, 17). The most representative measure of vitamin D status is the serum 25OHD concentration (18,19). Serum 25OHD is an excellent marker of vitamin D sufficiency, because it reflects the total stored quantity from both endogenous and exogenous sources (18). As serum 25OHD concentrations decrease, parathyroid hormone concentrations increase and positively influence the conversion of 25OHD to 1,25[(OH).sub.2]D, which subsequently maintains normal intestinal absorption of calcium. Therefore, 1,25[(OH).sub.2]D is not representative of the total body storage of vitamin D, because serum calcium and 1,25[(OH).sub.2]D concentrations will be normal or slightly increased during vitamin D deficiency, owing to secondary hyperparathyroidism (18, 20).

Risk Factors for Vitamin D Deficiency

Risk factors for developing vitamin D deficiency, or lower serum vitamin D concentrations, include an age >65 years (21), dark skin pigmentation, obesity (from storage in adipose tissue (22)), kidney and/or liver disease (23), disorders affecting fat absorption (e.g., celiac disease, Crohn disease, ulcerative colitis, some types of bariatric surgery), and end-organ insensitivity to 1,25[(OH).sub.2]D. In addition, 25OHD deficiency is also known to be related to environmental variables that lead to decreased exposure to ultraviolet light, such as institutionalization, decreased outdoor physical activity, and frailty (24).

Potential Mechanisms for an Association between Vitamin D Deficiency and CHD

Vitamin D receptors (VDRs) have been identified in many tissues, including vascular smooth muscle cells (25), cardiomyocytes, and coronary arteries (26, 27). Given the presence of VDRs in the vascular system, including the coronary arteries, there are several bio logically plausible pathways through which vitamin D could lead to improved cardiovascular health. Activation of the VDRs, for instance, has been shown to inhibit vascular smooth muscle cell proliferation, which is believed to be cardioprotective (28). Some studies have associated higher 25OHD concentrations and/or vitamin D supplementation with a systemic antiinflammatory state via effects on interleukins, C-reactive protein, and antiinflammatory cytokines--a milieu which, again, is believed to foster cardioprotection (29-31). Vitamin D may control blood pressure through its regulatory effects on the renin-angiotensin-aldosterone system (32). Limited research has suggested that vitamin D supplementation can decrease the incidence of impaired glucose tolerance and diabetes mellitus (33, 34), along with improving values for lipid parameters (35). Furthermore, the results of various studies have suggested a link between vitamin D and a lower likelihood of autoimmune conditions such as rheumatoid arthritis (36), diabetes (both type 1 and type 2) (37, 38), and multiple sclerosis (39).

Observational Data

Much of the excitement concerning a correlation between vitamin D deficiency and CHD stems from observational data. For example, Giovannucci et al. (9) followed 18 000 healthy male participants for 10 years. Individuals with vitamin D deficiency, defined as serum 25OHD concentrations [less than or equal to]15 ng/mL ([less than or equal to]38 nmol/ L), had a greater risk of a myocardial infarction than men with 25OHD concentrations [greater than or equal to]30 ng/mL ([greater than or equal to]75 nmol/L) (9), with a relative risk of 2.42 (95% CI, 1.53-3.84; P < 0.001). The Framingham Offspring Study, a prospective analysis of 1739 individuals with 25OHD concentrations <15 ng/mL (<38 nmol/L), obtained an adjusted hazard ratio for a first-incident cardiovascular event of 1.6 (95% CI, 1.11-2.36; P = 0.01). Participants who had hypertension along with 25OHD deficiency had a hazard ratio of 2.1 (95% CI, 1.3-3.5; P = 0.003) for a first cardiovascular event (18). A meta-analysis of prospective but observational studies of 25OHD and cardiovascular events demonstrated a generally linear, inverse association up to 24 ng/mL (60 nmol/L) but revealed no further reductions (i.e., a threshold effect) at higher 25OHD concentrations (40).

Limitations of the Observational Data

Despite the considerable data demonstrating an association between vitamin D deficiency and poor cardiovascular outcomes, caution is advisable in interpreting the data from observational studies. Confounding by other lifestyle factors and a "healthy user" bias in non-randomized studies may play a role in the current evidence suggesting an association. For example, age must be carefully controlled in analyses, because older age (21) increases both the risk of vitamin D deficiency and the risk of myocardial infarction (41). Decreased dietary intake and poor nutritional status can each lead to vitamin D nutritional deficiency. The lower intake could be due to other disease(s) or general malnutrition, either of which could increase the likelihood of CHD. Decreased exposure to ultraviolet light can be due to less outdoor activity/exercise and hence lead to an increased risk of CHD and low 25OHD. An additional confounding risk factor is obesity, which both increases the risk of CHD and lowers 25OHD concentrations because 25OHD can be sequestered in adipose tissues (22).

Few observational studies are able to adjust fully for these confounding factors. Therefore, all of these risk factors, which are more likely to be associated with low 25OHD, may confound the relationship between 25OHD and CHD in nonrandomized studies. As we pointed out earlier, vitamin D has been associated with a systemic antiinflammatory milieu. Although relevant pathways may include a beneficial interaction between vitamin D and C-reactive protein, interleukins, and/or cytokines (29-31), vitamin D deficiency has also been suggested to be a direct consequence of an inflammatory condition or state (42).

Randomized Controlled Trials

Few prospective randomized clinical trials evaluating the effects of vitamin D supplementation on CHD have been conducted, and currently none of the prospective trials have prespecified CHD as the primary outcome (43-45). Among the sparse randomized trials that have assessed CHD--or CHD risk factors--as a secondary or tertiary outcome, no correlation has been identified for CHD, and few have been found for CHD risk factors (Table 1) (46-58). In a study of 327 men and women older than 65 years, individuals who received vitamin [D.sub.3] actually had an increased risk of coronary death (P < 0.001) (58). In a double-blind, placebo-controlled, randomized clinical trial in the UK conducted among 2686 men and women 65-85 years of age, participants received 100 000 IU of supplemental vitamin [D.sub.3] every 4 months (equivalent to approximately 833 IU daily) for 5 years (46). No beneficial CHD effect could be attributable to vitamin D (46). Additional results from the Women's Health Initiative suggested that postmenopausal women who received 400 IU/day of oral vitamin [D.sub.3] combined with 1000 mg/day of calcium had no reduction in their risk of CHD events or stroke (50). In additional prospective trials (from subanalyses of the Women's Health Initiative), calcium and vitamin [D.sub.3] supplementation was not found to improve blood pressure (49) or coronary artery calcium scores (53). Furthermore, there was no decrease in incident hypertension (59) or any prevention of or improvement in the metabolic syndrome or diabetes (47). An 8-week prospective trial of 151 male and female vitamin D-deficient adults randomized to receive 50 000 IU of vitamin [D.sub.3] or placebo found no improvement in lipid parameters (48). Two small prospective trials that evaluated endothelial function produced mixed results, with one showing no effect (51) and the other showing a short-term improvement in stroke patients with well-controlled hypertension; however, the effect was not sustained by the completion of the 16-week study (52).

Several small prospective studies have shown some improvement in CHD risk factors (55) and inflammation (30, 56). Additional data have shown no effect on glycemic control, however (54, 57). A recent prospective randomized, double-blind, placebo-controlled clinical trial assessed the change in systolic and diastolic blood pressures in a healthy black population randomized to oral placebo or to 1000, 2000, or 4000 IU/day vitamin [D.sub.3] for 3 months (60). The results of this study revealed a 1.4-mmHg decrease in systolic blood pressure for each additional 1000 IU/day increase in the vitamin [D.sub.3] dose (P = 0.04). Although the investigators found no statistically significant effect of oral vitamin [D.sub.3] on diastolic blood pressure, their study did reveal a 0.2-mmHg decrease in systolic blood pressure for each 1-ng/mL (2.5-nmol/L) increase in 25OHD (P = 0.02). Despite this significant effect of oral vitamin [D.sub.3] on systolic blood pressure, there appeared to be a threshold effect, with individuals receiving 2000 IU/day and 4000 IU/day of vitamin [D.sub.3] having similar results. Furthermore, those with baseline 25OHD concentrations [greater than or equal to]20 ng/mL ([greater than or equal to]50 nmol/L) experienced little benefit from supplementation, compared with participants with baseline 25OHD concentrations <20 ng/mL (<50 nmol/L), who had a 2.2-mmHg decrease in systolic blood pressure (P = 0.03). In addition, adjustment for baseline differences in blood pressure attenuated the study's findings. Whereas this trial was designed to assess change in blood pressure, it is noteworthy that most other trials were designed to assess bone health. Cardiovascular outcomes were not prespecified primary end points for most previous studies.

Metaanalyses of Randomized Trials

Several metaanalyses have evaluated both mortality and CHD risk with respect to their relationship to vitamin D supplementation. A metaanalysis of 18 randomized clinical trials including 57 311 individuals was published in 2008 (61). This analysis revealed a statistically significant 7% decrease in all-cause mortality in participants who received vitamin D supplementation (61); however, a subsequent metaanalysis by Rejnmark et al. (62), which included 24 randomized trials of patients receiving vitamin D supplementation, with or without oral calcium, showed similar results, but with the following important variation. Although the patients who received supplements of vitamin D and calcium had a similar 7% reduction in all-cause mortality, as was seen in the earlier study (61), the patients who received vitamin D alone did not have a significant decrease in mortality. These results raise a number of questions, including the role calcium may have in any potential beneficial effect related to vitamin D supplementation. In considering a role of supplemental vitamin D, a recent systematic review and metaanalysis identified randomized trials published through August 2010 in which patients were randomized to vitamin D supplementation or to no treatment (63). The outcome measures of interest included mortality, cardiovascular events, and CHD risk factors. A total of 51 studies were eligible. Of note is that the analysis was unable to identify statistically significant differences in any of the outcomes, including myocardial infarction, stroke, all-cause mortality, or such CHD risk factors as lipid fractions, glucose, and systolic and diastolic blood pressures. Most of the trials tested relatively low vitamin D doses, however.

Although the association between 25(OH)D deficiency and obesity is not new (22), the results of a recent large metaanalysis suggest that a higher body mass index leads to lower plasma 25(OH)D concentrations, implying a causative relationship. In contrast, lower 25(OH)D concentrations did not appear to lead to a high body mass index (64). If these findings are confirmed, strategies to decrease obesity could also lower the prevalence of 25(OH)D deficiency.

Current Recommendations

The Institute of Medicine (IOM) (44) and the Agency for Healthcare Research and Quality (AHRQ) (43) reviewed the literature related to vitamin D and health-related outcomes. Both concluded that although sufficient evidence existed to support a role for calcium and vitamin D related to skeletal health, evidence supporting effects on non-bone-related health outcomes was lacking (44, 45). The IOM recommended a dietary allowance of 600 IU/day for individuals 1-70 years of age, with 800 IU/day recommended for individuals older than 70 years (18, 61). The IOM and AHRQ reports have generated some controversy, and some investigators have stated that higher dietary allowances should be encouraged. The International Osteoporosis Foundation (IOF), for instance, recommends 800-1000 IU/day as the mean supplemental dose to achieve an appropriate plasma 25OHD concentration (65). The IOF adds that individuals at higher risk may require doses of up to 2000 IU/day to reach an appropriate concentration (65). The National Osteoporosis Foundation (NOF) recommends 400-800 IU/day of oral vitamin [D.sub.3] for adults <50 years of age and 800-1000 IU/day for those >50 years (66). In line with the IOF guidelines, the NOF has clarified that some people may need higher oral vitamin [D.sub.3] doses, with 4000 IU/ day noted as an upper limit of safety (66). Similarly, the Endocrine Society's clinical guideline recommends at least 600 IU/day for adults 19-50 years of age and 600-800 IU/day for those older than 50 years. They also point out that doses of 1500-2000 IU/day may be required for all adults to consistently raise plasma 25OHD concentrations to >30 ng/mL (>75 nmol/L) (67). Although controversy surrounds the 25OHD concentration to use as a cutpoint for vitamin D deficiency or insufficiency, the IOM suggests that a serum 25OHD concentration of at least 20 ng/mL (50 nmol/L) will meet the vitamin D requirements for [greater than or equal to]97.5% of the US and Canadian populations (68). As we discussed above, results of the recent study assessing oral vitamin [D.sub.3] and blood pressure (60) likewise support a 25OHD concentration [greater than or equal to]20 ng/mL as being adequate; only individuals with 25OHD concentrations <20 ng/mL at baseline experienced a significant improvement in systolic blood pressure with vitamin [D.sub.3] supplementation (60).

Laboratory Testing

The current assays available for 25OHD testing include antibody-based methods and liquid chromatography. The methodologies for plasma 25OHD analyses, however, have changed greatly over the years. The early testing methods used competitive protein-binding assays, which were difficult to perform and lacked consistency. The introduction of early liquid chromatography techniques in the 1970s allowed, for the first time, the ability to detect 25OH[D.sub.2] and 25OH[D.sub.3] separately. As liquid chromatography assays were being refined in the 1980s, antibody-based assays were introduced. More recently, antibody assays have been modified to accommodate the automated multiwell plate format, which has made these assays quite popular. A notable drawback is the inability to distinguish between 25OH[D.sub.2] and 25OH[D.sub.3]. It is also noteworthy that much of the past research related to plasma vitamin D concentrations were performed with antibody-based techniques. The variety of testing methods and questions about the reliability of testing also add to the complexity of interpreting previous research. Most recently, the liquid chromatography method has advanced substantially with the incorporation of a tandem mass spectrometer--the liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique. This improvement produces data with very high specificity and sensitivity, along with outstanding reproducibility (44).

Because a majority of the previous data were produced with the antibody-based assays, it is important to point out the concern about inconsistencies between testing methods. Research that has incorporated inter-laboratory comparisons suggests a high and concerning degree of variation (44). These results have led to external quality-assurance programs, including NIST reference standards (69, 70), which use a "validated" LC-MS/MS technique for calibration (44). A Standard Reference Material and a calibration solution are now available through the NIST to help assure the accuracy and reliability of 25OHD measurements (44).

A study by Lia et al. compared DiaSorin LIAISON results with those for the LC-MS/MS assay (selected as the nominal gold standard) obtained with same participant samples and found a vitamin D deficiency rate that was 16% to 29% higher, respectively, based just on the laboratory test used. Furthermore, the DiaSorin RIA has been shown to produce lower serum 25OHD values than the LC-MS/MS method (71). The LCMS/MS assay, which is considered inherently more accurate (71) with its high sensitivity, high specificity, and better reproducibility, tends to produce values that are slightly higher than obtained with the RIA techniques (71). Some have argued that LC-MS/MS results may need to be adjusted downward according to a mathematical formula, whereas others have suggested that DiaSorin RIA results may need to be corrected upward (71). Regardless, the value of using consistent and reliable laboratory testing is therefore of paramount importance, and LC-MS/MS is currently the preferred laboratory assay.

For quality assurance, it is critically important that test measurements be performed on standardized samples, with the inclusion of NIST samples and split-replicate samples for laboratory assessment. Such protocols allow laboratories to compute means, SDs, and CVs. Samples should be protected from direct sunlight to ensure the accuracy and precision of assays (30, 44, 72). The new NIST reference standards offer hope that 25OHD measurements can achieve improved accuracy and reliability and thus diminish the variation between tests and laboratory centers seen in the past (44).

Future Research Directions

Although our understanding of vitamin D deficiency and its ramifications is rapidly expanding, there is still much to learn. Several large-scale randomized trials of moderate to high dosages of vitamin D supplementation in cardiovascular disease (CVD) prevention are being conducted in the US and throughout the world. As one example, the Vitamin D and Omega-3 Trial (VITAL) (J.E. Manson, principal investigator) is a randomized, double-blind, placebo-controlled clinical trial of 20 000 US men and women older than 50 years. It tests 2000 IU/day of oral vitamin [D.sub.3] and [omega]-3 fatty acid supplements in a 2 x 2 factorial design, with CVD and cancer as prespecified primary outcomes (73). Results are expected in 2017. While we await the results of VITAL and other ongoing randomized trials of vitamin D, it is also important to point out that many of the trials will analyze the effects of vitamin [D.sub.3] supplementation in a general population of patients with and patients without 25OHD deficiency. There may be value, therefore, in stratifying by baseline concentrations or subsequently analyzing results in vitamin D-deficient patients (74).

Although data have suggested that the VDR concentration may be inversely correlated with the degree of coronary artery atherosclerosis (26), the link to or relationship with the plasma 25OH[D.sub.3] concentration remains unclear. A recent study suggested that individuals with the highest plasma 25OH[D.sub.3] concentration and the lowest VDR abundance had the greatest degree of coronary artery atherosclerosis (27), but these findings need corroboration. If confirmed, they suggest a therapeutic-window phenomenon, that high 25OH[D.sub.3] concentrations may be detrimental above an upper threshold (18). Data have also suggested a strong link between 25OH[D.sub.3] deficiency and race/heritability (75-79). A recent study (76) indicated that individual differences in 25OHD concentrations have both genetic and environmental associations and that the relative contributions to CHD outcomes remains unclear. In this particular study, the variation attributable to genetics was predominantly demonstrated in the winter when ultraviolet exposure was minimal but was not apparent in the summer months, implying that environmental factors (mostly sun exposure) may compensate for vitamin D deficiency related to genetics (77).

As the review above indicates, we are clearly in need of well-designed and adequately powered prospective randomized trials with vitamin D supplementation and CHD or CHD biomarkers as primary outcomes. It will be important to determine whether supplementation makes a clinically meaningful difference for CHD and whether the baseline 25OHD concentration modifies the response. Such trials will help to elucidate whether low vitamin D concentrations represent a marker for other processes, are indicators of genetic predisposition to disease, or are causally related to risk. On the assumption that vitamin D supplementation truly is of value for preventing CVD, what is the optimal dose, and what role does calcium supplementation play in the equation? Furthermore, does a therapeutic-window phenomenon exist such that not only lower but also higher serum concentrations can be detrimental? In contrast, an examination of the completed randomized, prospective placebo-controlled trials (Table 1) shows that a major weakness of many of these trials is that they tested lower vitamin D doses than currently postulated to be of benefit for extraskeletal outcomes. What role does the VDR play, would a VDR agonist be of benefit, or are there ways to prevent VDR loss and hence delay the onset of coronary atherosclerosis? As we await the results of ongoing research, we eagerly await answers to these questions.


The IOM review suggested that higher plasma concentrations of vitamin D have not been shown to reduce chronic disease beyond the established bone health benefits, but it recommended that more targeted research continue to explore the role of vitamin D supplementation in preventing CVD and other chronic illnesses. Despite plausible biological mechanisms for a role of vitamin D in cardioprotection, a cause-and-effect relationship has not yet been established. Although observational studies point to a potential association, such data are hampered by potential confounding and selection factors. A correlation found in an observational study does not prove causality, and so the available randomized-trial data do not yet demonstrate a clear benefit. Therefore and in line with the recommendations from the IOM and the AHRQ, additional research is needed to advance our knowledge of this subject. While clinicians await the results of ongoing randomized trials, including VITAL and several other trials worldwide, they should be cautious to avoid not only overtreatment with high-dose vitamin D supplementation but also undertreatment until we know the true risks and benefits.

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, oranalysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

Authors' Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest:

Employment or Leadership: None declared.

Consultant or Advisory Role: None declared.

Stock Ownership: None declared.

Honoraria: None declared.

Research Funding: J.E. Manson, National Institutes of Health (CA138962) for VITamin D and OmegA-3 TriaL (VITAL), a randomized trial of vitamin D and omega-3 supplementation in preventing cancer and cardiovascular disease.

Expert Testimony: None declared.

Patents: None declared.


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Peter F. Schnatz [1,2,3,4] and JoAnn E. Manson [5] *

Departments of [1] Obstetrics and Gynecology and [2] Internal Medicine, The Reading Hospital and Medical Center, Reading, PA; Departments of [3] Obstetrics and Gynecology and [4] Internal Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA; [5] Department of Medicine, Division of Preventive Medicine, Brigham and Women's Hospital/Harvard Medical School, Boston, MA.

* Address correspondence to this author at: Brigham and Women's Hospital, 900 Commonwealth Ave., 3rd Floor, Boston, MA 02215. Fax 617-731-3843; e-mail

Received June 19, 2013; accepted October 10, 2013.

Previously published online at DOI: 10.1373/clinchem.2013.211037

[6] Nonstandard abbreviations: CHD, coronary heart disease; 25OHD, 25- hydroxyvitamin D; 1,25[(OH).sub.2]D, 1,25-dihydroxyvitamin D; VDR, vitamin D receptor; IOM, Institute of Medicine; AHRQ, Agency for Healthcare Research and Quality; IOF, International Osteoporosis Foundation; NOF, National Osteoporosis Foundation; LC-MS/MS, liquid chromatography-tandem mass spectrometry; CVD, cardiovascular disease; VITAL, Vitamin D and Omega-3 Trial.
Table 1. Prospective randomized trials of vitamin D supplementation
and CHD events or CVD risk factors. (a)

Design            Primary outcome          Study outcome

DB, (b) PC, RCT   Colorectal cancer        Change in SBP and
                    prevention study         DBP

DB, PC, RCT       Changes in brachial      Same as primary
                    artery FMV,              outcomes
                    carotid-femoral PWV,
                    and aortic
                    augmentation index

DB, PC, RCT       Change in small LDL      Other lipid
                    particle number          fractions

DB, PC, RCT       BP, FMV of the           Same as primary
                    brachial artery,         outcomes
                    cholesterol, and
                    other markers of
                    vascular health

DB, PC, RCT       Hip fractures            CAC score

DB, PC, RCT       Fasting serum            Same as primary
                    lipids, BP, and oral     outcomes
                    glucose tolerance

PC, RCT           Glycemic control in      Same as primary
                    patients with type 2     outcomes

DB, PC, RCT       Weight loss and          Same as primary
                    traditional +            outcomes (PTH,
                    nontraditional CVD       TG, and
                    risk markers             inflammatory

DB, PC, RCT       Hip fractures            Incident DM

DB, PC, RCT       Hip fractures            Change in BP and
                                             development of

DB, PC, RCT       Hip fractures            Risk of CHD

DB, PC, RCT       Survival rate,           Same as primary
                    biochemical              outcomes
                    variables, and
                    cytokine profile

DB, PC, RCT       Fracture incidence       Same as primary
                    and total mortality      outcome;
                    by cause                 additional data
                                             assessing CVD

DB, PC, RCT       Fractures                Coronary

Design            Summary of study,        Length and
                  sample size, patient     follow-up
                  age, an a route/dose
                  of treatment

DB, (b) PC, RCT   Blacks (n = 283;         6 Months
                    30-80 years; median,
                    51 years) randomized
                    for 3 months to oral
                    placebo, 1000, 2000,
                    or 4000 IU/day
                    followed by
                    treatment for 3 more

DB, PC, RCT       Postmenopausal women     4 Months
                    [n = 114; mean (SD)
                    age, 63.9 (3) years]
                    with serum 250HD
                    concentrations >10
                    and <60 ng/mL;
                    received 2500 IU
                    Vit[D.sub.3] or
                    placebo daily
DB, PC, RCT       VitD-insufficient        8 Weeks
                    (250HD [less than or
                    equal to]20 ng/mL)
                    male and female
                    adults (n = 151);
                    received 50 000 IU
                    Vit[D.sub.3] weekly
DB, PC, RCT       Patients (n = 58;        16 Weeks of
                    mean age, 67 years)      follow-up
                    received 100 000 IU
                    oral Vit[D.sub.2] or
                    placebo at baseline

DB, PC, RCT       Ca/D trial (1)           7 Years
                    nested within WHI
                    hormonal trial (2)
                    (estrogen among
                    women who underwent
                    hysterectomy). Women
                    (n = 754; age, 50-59
                    years) received
                    daily calcium
                    carbonate (1000 mg
                    elemental calcium)
                    and Vit[D.sub.3]
                    (400 IU)
DB, PC, RCT       Obese or overweight      1 Year
                    patients (n = 438;
                    21-70 years)
                    Vit[D.sub.3] (40 000
                    or 20 000 IU/week)
                    or placebo; all
                    received 500 mg
                    calcium daily; 330
                    patients completed
PC, RCT           Participants (n =        6 Months
                    36) received
                    Vit[D.sub.3] (40 000
                    IU/week) or placebo
DB, PC, RCT       Participants (n =        12 Months
                    200; mean baseline
                    250HD, 30 nmol/L)
                    received 3320 IU/day
                    VitD or placebo
                    while participating
                    in weight-reduction

DB, PC, RCT       WHI Ca/D trial of        7 Years of
                    postmenopausal women     follow-up
                    (n = 36 282; age,
                    5O-79 years);
                    received 1000 mg
                    elemental calcium +
                    400 IU Vit[D.sub.3]
DB, PC, RCT       WHI Ca/D trial of        7 Years of
                    postmenopausal women   follow-up
                    (n = 36 282);
                    received 1000 mg
                    elemental calcium +
                    400 IU Vit[D.sub.3]
DB, PC, RCT       WHI Ca/D trial of        7 Years of
                    postmenopausal women     follow-up
                    (n = 36 282; age,
                    BO- 79 years);
                    received BOO mg
                    calcium carbonate +
                    200 IU Vit[D.sub.3]
                    twice daily
DB, PC, RCT       Participants (n =        9-Month
                    123) received 2000       intervention,
                    IU Vit[D.sub.3] and      15 months
                    500 mg Ca/D daily        of follow-up
                    (D+ group), or
                    placebo and 500 mg
                    Ca/D daily (D-
                    group); 93 patients
                    completed study

DB, PC, RCT       2686 Participants        5 Years, Britain
                    (2037 men and 649
                    women; age, 65-85
                    years) randomized to
                    receive 100 000 IU
                    Vit[D.sub.3] every 4
DB, PC, RCT       327 Patients (57 men     9 Months
                    and 270 women >65
                    years; mean, 79.5
                    years) received
                    daily all possible
                    combinations of 3 g
                    calcium carbonate,
                    1000 IU
                    Vit[D.sub.3], 2.5 mg
                    and/or placebos

Design            Outcomes related to    Preexisting
                  CHD or CHD risk        conditions or
                  factors                disease?

DB, (b) PC, RCT   A--1.4-mmHg change     Generally healthy
                  in SBP for each        patients. Patients
                  additional 1000 lU-    with preexisting
                  day of Vit[D.sub.3]    disorders of the
                  (P = 0.04). No         parathyroid or
                  significant effect     calcium metabolism;
                  on DBP, Each 1-ng-     patients with type I
                  mL increase in 250HD   DM, sarcoidosis,
                  accompanied by a--     malignancy, or
                  0.2-mmHg change in     thyroid disease
                  SBP (P = 0.02)         excluded
DB, PC, RCT       VitD supplementation   Generally healthy,
                  did not improve        community- dwelling,
                  endothelial            ambulatory women
                  function, arterial     from Madison, Wl;
                  stiffness, or          patients with CVD
                  inflammation           excluded

DB, PC, RCT       VitD repletion         Increased risk for
                  failed to improve      CVD (with at least 1
                  lipid profile          of numerous
                                         significant CVD risk

DB, PC, RCT       High-dose oral VitD    History of stroke
                  supplementation did    with baseline 250HD
                  not improve BP but     concentrations <75
                  produced short- term   nmol/L
                  improvement in
                  endothelial function
                  in stroke patients
                  with well-
                  controlled baseline
                  BP, which was not
                  sustained by end of
DB, PC, RCT       Treatment and          Generally healthy
                  placebo groups were    postmenopausal women
                  not different in CAC
                  plaque burden
                  measured at end of

DB, PC, RCT       No significant         Overweight or obese
                  effect of VitD on      patients
                  glucose tolerance,
                  BP, or serum lipids

PC, RCT           No significant         Type 2 DM treated
                  effect of VitD on      with metformin and
                  glucose metabolism     bedtime insulin

DB, PC, RCT       No adverse effect of   Overweight
                  VitD on weight loss
                  but significantly
                  decreased PTH, TG,
                  TNF (although LDL
                  significantly) in
                  individuals with
                  inadequate VitD
                  status while
                  participating in
DB, PC, RCT       No beneficial          Generally healthy
                  effects in reducing    postmenopausal women
                  DM incidence or
                  metabolic syndrome

DB, PC, RCT       No significant         Generally healthy
                  beneficial effect on   postmenopausal women
                  BP or prevention of
                  incident HTN

DB, PC, RCT       No beneficial CHD      Generally healthy
                  effects attributable   postmenopausal women
                  to Ca/D

DB, PC, RCT       Vit[D.sub.3] reduced   CHF
                  inflammatory milieu
                  in CHF patients;
                  increased, but
                  improvement in PTH
                  and TNF; no
                  difference in
                  survival, however
DB, PC, RCT       No beneficial CVD      Patients recruited
                  effects attributable   from the general
                  to VitD                community; excluded
                                         if history of renal
                                         stones, sarcoidosis,
                                         or malignancy

DB, PC, RCT       Coronary mortality
                  higher among those
                  taking all 3 active
                  significant increase
                  in coronary deaths,
                  most significantly
                  (P < 0.001) in
                  patients receiving
                  Vit[D.sub.3] and

Design            Reference

DB, (b) PC, RCT   Forman et al.

DB, PC, RCT       Gepner et al.

DB, PC, RCT       Ponda et al.

DB, PC, RCT       Witham et al.

DB, PC, RCT       Manson
                  et al. (53)

DB, PC, RCT       Jorde et al.

PC, RCT           Jorde et al.

DB, PC, RCT       Zittermann et
                  al. (55)

DB, PC, RCT       DeBoer et al.

DB, PC, RCT       Margolis
                  et al. (49)

DB, PC, RCT       Hsia et al.

DB, PC, RCT       Schleithoff
                  et al. (56)

DB, PC, RCT       Trivedi et al.

DB, PC, RCT       Inkovaara
                  et al. (58)

(a) Note that because this article is not an all-inclusive systematic
review, this table may not list all randomized controlled trials
(RCTs) reporting on vitamin D supplementation and CHD risk factors
as well as CHD events.

(b) DB, double-blind; PC, placebo controlled; SBP, systolic blood
pressure; DBP, diastolic blood pressure; Vit[D.sub.3], vitamin D3;
DM, diabetes mellitus; FMV, flow-mediated vasodilation; PWV, pulse
wave velocity; BP, blood pressure; CAC, coronary artery calcium;
WHI, Women's Health Initiative; Ca/D, calcium and vitamin D; PTH,
parathyroid hormone; TG, triglycerides; TNF, tumor necrosis factor;
HTN, hypertension; CHF, congestive heart failure.
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Author:Schnatz, Peter F.; Manson, JoAnn E.
Publication:Clinical Chemistry
Article Type:Report
Date:Apr 1, 2014
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