The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know

Vitamin D levels predict all-cause and cardiovascular disease mortality in subjects with the metabolic syndrome: the Ludwigshafen Risk and Cardiovascular Health (LURIC) Study

OBJECTIVE

Optimal vitamin D levels are associated with reduced cardiovascular and all-cause mortality. We investigated whether optimal 25-hydroxyvitamin D (25[OH]D) is protective in individuals with the metabolic syndrome.

RESEARCH DESIGN AND METHODS

The Ludwigshafen Risk and Cardiovascular Health (LURIC) study is a cohort study of subjects referred for coronary angiography between 1997 and 2000, from which 1,801 with the metabolic syndrome were investigated. Mortality was tracked for a median of 7.7 years. Multivariable survival analysis was used to estimate the association between 25(OH)D levels and mortality.

RESULTS

Most subjects (92%) had suboptimal levels of 25(OH)D (<75 nmol/L), with 22.2% being severely deficient (<25 nmol/L). During follow-up, 462 deaths were recorded, 267 (57.8%) of which were cardiovascular in origin. After full adjustment, including the metabolic syndrome components, those with optimal 25(OH)D levels showed a substantial reduction in all-cause (hazard ratio [HR] 0.25 [95% CI 0.13-0.46]) and cardiovascular disease mortality (0.33 [0.16-0.66]) compared with those with severe vitamin D deficiency. For specific cardiovascular disease mortality, there was a strong reduction for sudden death (0.15 [0.04-0.63]) and congestive heart failure (0.24 [0.06-1.04]), but not for myocardial infarction. The reduction in mortality was dose-dependent for each of these causes.

CONCLUSIONS

Optimal 25(OH)D levels substantially lowered all-cause and cardiovascular disease mortality in subjects with the metabolic syndrome. These observations call for interventional studies that test whether vitamin D supplementation provides a useful adjunct in reducing mortality in these subjects.

Vitamin D and fertility: a systematic review

BACKGROUND

Vitamin D has been well-known for its function in maintaining calcium and phosphorus homeostasis and promoting bone mineralization. There is some evidence that in addition to sex steroid hormones, the classic regulators of human reproduction, vitamin D also modulates reproductive processes in women and men.

AIM

The aim of this review was to assess the studies that evaluated the relationship between vitamin D and fertility in women and men as well as in animals.

METHODS

We performed a systematic literature search in Pubmed for relevant English language publications published until October 2011.

RESULTS AND DISCUSSION

The vitamin D receptor (VDR) and vitamin D metabolizing enzymes are found in reproductive tissues of women and men. Vdr knockout mice have significant gonadal insufficiency, decreased sperm count and motility, and histological abnormalities of testis, ovary and uterus. Moreover, we present evidence that vitamin D is involved in female reproduction including IVF outcome (clinical pregnancy rates) and polycystic ovary syndrome (PCOS). In PCOS women, low 25-hydroxyvitamin D (25(OH)D) levels are associated with obesity, metabolic, and endocrine disturbances and vitamin D supplementation might improve menstrual frequency and metabolic disturbances in those women. Moreover, vitamin D might influence steroidogenesis of sex hormones (estradiol and progesterone) in healthy women and high 25(OH)D levels might be associated with endometriosis. In men, vitamin D is positively associated with semen quality and androgen status. Moreover, vitamin D treatment might increase testosterone levels. Testiculopathic men show low CYP21R expression, low 25(OH)D levels, and osteoporosis despite normal testosterone levels.

Hypovitaminosis D and prevalent asymptomatic vertebral fractures in Moroccan postmenopausal women

BACKGROUND

Hypovitaminosis D is associated to accentuated bone loss. However, association between osteoporotic vertebral fractures (VFs) and vitamin D status has not been clearly established.

OBJECTIVE

To determine serum vitamin D status and to assess the association of vitamin D status with bone mineral density (BMD) and asymptomatic VFs prevalence using vertebral fracture assessment (VFA) in a cohort of Moroccan menopausal women.

METHODS

from June to September 2010, 178 menopausal women 50 years old and over were enrolled in this cross-sectional study. The mean ± SD (range) age, weight, height and BMI were 58.8 ± 8.2 (50 to 79) years, 73.2 ± 13.8 (35 to 119) Kgs, 1.56 ± 0.06 (1.43 - 1.79) m and 29.8 ± 5.9 (17.5 - 49.8) kg/m2, respectively. VFA images and scans of the lumbar spine and proximal femur were obtained using a GE Healthcare Lunar Prodigy densitometer. VFs were defined using a combination of Genant semiquantitative approach and morphometry. Serum levels of 25-hydroxyvitamin D (25(OH)D) were measured.

RESULTS

Among the 178 women, 45 (25.2%) had densitometric osteoporosis, and on VFA, VFs (grade 2 or 3) were detected in 20.2% while grade 1 were identified in 33.1%. The mean values of serum levels of 25(OH)D were 15.8 ± 11.6 ng/ml (range: 3.0 - 49.1) with 152 patients (85.3%) having levels <30 ng/ml (insufficiency) and 92 (51.6%) <10 ng/ml (deficiency). Stepwise regression analysis showed that presence of VFs was independently related to age, 25(OH)D and densitometric osteoporosis.

CONCLUSION

our study shows that advanced age, hypovitaminosis D and osteoporosis are independent risk factors for asymptomatic VFs in Moroccan postmenopausal women.

Vitamin D and physical performance in elderly subjects: the Pro.V.A study

Background

The role of Vitamin D in musculoskeletal functionality among elderly people is still controversial. We investigated the association between serum 25-hydroxyvitamin D (25OHD) levels and physical performance in older adults.

Methods

2694 community-dwelling elderly women and men from the Progetto Veneto Anziani (Pro.V.A.) were included. Physical performances were assessed by: tandem test, 5 timed chair stands (TCS), gait speed, 6-minute walking (6 mW) distance, handgrip strength, and quadriceps strength. For each test, separate general linear models and loess plots were obtained in both genders, in relation to serum 25OHD concentrations, controlling for several potential confounders.

Results

Linear associations with 25OHD levels were observed for TCS, gait speed, 6 mW test and handgrip strength, but not for tandem test and quadriceps strength. After adjusting for potential confounders, linear associations with 25OHD levels were still evident for the 6 mW distance in both genders (p = .0002 in women; <.0001 in men), for TCS in women (p = .004) and for gait speed (p = .0006) and handgrip strength (p = .03) in men. In loess analyses, performance in TCS in women, in gait speed and handgrip strength in men and in 6 mW in both genders, improved with increasing levels of 25OHD, with most of the improvements occurring for 25OHD levels from 20 to 100 nmol/L.

Conclusion

lower 25OHD levels are associated with a worse coordination and weaker strength (TCS) in women, a slower walking time and a lower upper limb strength in men, and a weaker aerobic capacity (6 mW) in both genders. For optimal physical performances, 25OHD concentrations of 100 nmol/L appear to be more advantageous in elderly men and women, and Vitamin D supplementation should be encouraged to maintain their 25OHD levels as high as this threshold.

Relationship of vitamin D deficiency to clinical outcomes in critically ill patients

BACKGROUND

Despite the numerous disease conditions associated with vitamin D deficiency in the general population, the relationship of this deficiency to outcome in critically ill patients remains unclear. The objective of this study is to determine the burden of vitamin D deficiency in intensive care unit (ICU) patients and determine if it is associated with poor patient outcomes.

METHODS

The authors conducted an analysis of samples collected from a prospective study of 196 patients admitted to a medical/surgical ICU in a tertiary care hospital. They measured serum 25-hydroxyvitamin D at admission and up to 10 days following admission and followed patients prospectively for 28-day outcomes.

RESULTS

Of analyzable patients, 50 (26%) were deficient (≤30 nmol/L) and 109 (56%) were insufficient (>30 and ≤60 nmol/L). Baseline 25(OH)D levels decreased significantly in all patients after 3 days in the ICU and remained significantly lower through 10 days (P < .001). 25(OH)D status was not significantly associated with 28-day all-cause mortality (hazard ratio [HR], 0.89; 95% confidence interval, [CI] 0.37-2.24). Higher levels of 25(OH)D were associated with a shorter time-to-alive ICU discharge (HR, 2.11; 95% CI, 1.27-3.51). 25(OH)D-deficient patients showed a nonstatistically significant trend toward a higher infection rate (odds ratio [OR], 3.20; 95% CI, 0.784-13.07; P = .11) compared with patients with sufficient levels of 25(OH)D.

CONCLUSIONS

This study demonstrates significant decreases in vitamin D status over the duration of the patient's ICU stay. Low levels of vitamin D are associated with longer time to ICU discharge alive and a trend toward increased risk of ICU-acquired infection.

Vitamin D: an essential component for skeletal health

Vitamin D deficiency is increasing worldwide. Ultraviolet rays are supposed to provide humans over 80% of our vitamin D requirement; the rest is received through diet and supplements. In addition to enhancing calcium absorption from the intestine and mineralization of the osteoid tissue, vitamin D has many other physiological effects, including neuromodulation, improving muscle strength and coordination, insulin release, immunity and prevention of infections, and curtailing cancer. Whether the increased incidence of vitamin D deficiency is related to increased incidences of nonskeletal disorders remains to be determined. Serum levels of 25-hydroxyvitamin [25(OH)D] above 30 ng/mL indicate vitamin D sufficiency. An additional 1,000 IU of vitamin D/day is sufficient for most lighter-skinned individuals, whereas an extra 2,000 IU/day is needed by the elderly and dark-skinned individuals to maintain normal 25(OH)D levels. Additional research is needed to clarify the relationship between vitamin D and the nonskeletal systems, nonclassic functions, and targets of vitamin D.

Immunomodulators for multiple sclerosis may ameliorate spinal bone loss

BACKGROUND

The effect of immunomodulator therapy (IMT) for multiple sclerosis (MS) on bone turnover is unknown.

AIM

The aim of this study was to assess bone turnover in MS patients on IMT.

METHODS

MS patients (n = 29) on maintenance IMT had repeat measurement of bone mineral density (BMD) after a 4.0 ± 0.4 years; bone turnover markers (BTM) were measured at the time of repeat BMD.

RESULTS

BMD was unchanged at the spine but declined at the hip. BTMs, both resorption and formation, were reduced compared to normative range that may indicate an anti-resorptive action of IMT. Significant negative correlations were noted between BTMs and changes in BMD at spine but not hip.

CONCLUSION

These observations suggest that IMT may have a beneficial effect on spinal bone by an antiresorptive action. A prospective study of the effect of IMT on BMD and bone turnover is warranted.

A dermatologist's perspective on vitamin D

Vitamin D is a fat-soluble steroid hormone that is crucial for human health and has recently generated controversy regarding its role in human health and disease. In this Special Article, we discuss our dermatologic perspective on vitamin D in a question-and-answer format. We discuss methods of obtaining vitamin D, including cutaneous photobiosynthesis, diet, and supplements and include the recent US Institute of Medicine recommendations. Other reviewed topics include the associations among skin pigmentation, climate, photoprotection, and vitamin D levels. We also elaborate on the popular interest in sun exposure as a method of normalizing vitamin D levels in the context of the risks of solar and artificial radiation. We also discuss groups at risk for vitamin D inadequacy, the need for testing serum vitamin D levels, and the role of phototherapy in patients with malabsorption conditions and hypervitaminosis D, with a focus on patients with sarcoidosis. Finally, we summarize our recommendations on vitamin D.

Is vitamin D status relevant to metabolic syndrome?

Review of the evidence on hypovitaminosis D as a risk factor for metabolic syndrome and its sequelae, T2DM and CVD, suggests long-term vitamin D repletion could reduce these risks. There is mechanistic evidence for protective effects for MetS and the balance of evidence, (cross-sectional and prospective), supports this postulate. Much of the data so far available from randomized controlled trials is weakened by inadequate power, low vitamin D dosages, starting supplementation too late in life or after MetS disorders have developed or, most importantly, by non-inclusion of many recognizable confounders. On balance, therefore, maintenance of US 2010 recommended intakes for bone protection has the potential to prove protective for MetS. Supplementation has been shown to increase survival in patients with cardiac disorders; whether higher doses would provide useful protection for apparently healthy people in the general population awaits the outcomes of ongoing randomized-controlled trials that, it is hoped, will prove or disprove causality for hypovitaminosis D in MetS and its long-term ill-effects.

Effects of sunlight and diet on vitamin D status of pulmonary tuberculosis patients in Tbilisi, Georgia

OBJECTIVE

Vitamin D deficiency is common in tuberculosis (TB) and this may modulate immune responses. This study investigated vitamin D status in patients with TB and examined the sources of vitamin D in Tbilisi, Georgia.

METHODS

We measured plasma 25-hydroxyvitamin D (25[OH]D) and dietary vitamin D intake in patients with pulmonary TB (n = 85) in Tbilisi, Georgia. To determine the impact of season on vitamin D status, we tested the in vitro conversion of 7-dehydrocholesterol (7-DHC) to previtamin D(3) after sunlight exposure.

RESULTS

In subjects with TB, mean plasma 25(OH)D concentrations were 14.4 ± 7.0 ng/mL, and vitamin D insufficiency (25[OH]D <30 ng/mL) occurred in 97% of subjects. The dietary sources of vitamin D were mainly fish, eggs, and butter. The daily intake was well below recommended daily intakes in subjects with TB (172 ± 196 IU). The conversion of 7-DHC to previtamin D(3) was undetectable from October to March and highest in June and July from 11:00 to 14:00 h.

CONCLUSION

An insufficient vitamin D dietary intake and a limited production of vitamin D from sunlight for most of the year may explain the high prevalence of vitamin D insufficiency in patients with TB in Tbilisi.

Hypercalcemia in children receiving pharmacologic doses of vitamin D

Vitamin D deficiency causes rickets, requiring vitamin D at doses greater than daily dietary intake. Several treatment regimens are found in the literature, with wide dosing ranges, inconsistent monitoring schedules, and lack of age-specific guidelines. We describe 3 children, ages 2 weeks to 2 and 9/12 years, who recently presented to our institution with hypercalcemia and hypervitaminosis D (25-hydroxyvitamin D levels >75 ng/mL), associated with treatment of documented or suspected vitamin D-deficient rickets. The doses of vitamin D used were within accepted guidelines and believed to be safe. The patients required between 6 weeks and 6 months to correct the elevated serum calcium, with time to resolution of hypercalcemia related to age and peak serum calcium, but not to peak 25-hydroxyvitamin D level. With recent widespread use of vitamin D in larger dosages in the general population, we provide evidence that care must be taken when using pharmacologic dosing in small children. With limited dosing guidelines available on a per weight basis, the administration of dosages to infants that are often used in older children and adults has toxic potential, requiring a cautious approach in dose selection and careful follow-up. Dosage recommendations may need to be reassessed, in particular, where follow-up and monitoring may be compromised.

Effect of follow-up time on the relation between prediagnostic serum 25-hydroxyvitamin D and all-cause mortality rate

Evidence continues to mount that vitamin D reduces the risk and mortality rates of many types of disease. However, evidence from prospective cohort studies is sometimes weaker than that from case-control and ecological studies. A suggested reason for this discrepancy is that, because serum levels of 25-hydroxyvitamin D [25(OH)D] change over time, a single 25(OH)D concentration measurement taken at study enrollment does not reliably indicate 25(OH)D concentration related to the health outcome. To evaluate this suggestion further, this paper plots results from 12 prospective cohort studies of all-cause mortality rate vs. follow-up time. The regression fit to the hazard ratio per 20-nmol/l increase in serum 25(OH)D concentration vs. time increased from 0.82 (95% CI, 0.67-1.02) for 6 y to 0.96 (95% CI, 0.90-1.01) for 14 y. The value extrapolated for zero follow-up time was 0.72 (95% CI, 0.50-1.03), giving a hazard ratio reduction 3.5 times higher than the standard result from the meta-analysis [0.92 (95% CI, 0.89-0.95)]. Using the example of the Vitamin D Pooling Project of Rarer Cancers, this paper also discusses follow-up time's effect in interpreting prospective cohort studies of cancer outcome. This paper recommends that meta-analyses of prospective cohort studies account for follow-up time and, if possible, that studies measure serum 25(OH)D concentration every 2-4 y.

Vitamin D threshold to prevent aromatase inhibitor-related bone loss: the B-ABLE prospective cohort study

Aromatase inhibitor (AI)-related bone loss is associated with increased fracture rates. Vitamin D might play a role in minimising this effect. We hypothesised that 25-hydroxy-vitamin D concentrations [25(OH)D] after 3 months supplementation might relate to bone loss after 1 year on AI therapy. We conducted a prospective cohort study from January 2006 to December 2011 of a consecutive sample of women initiating AI for early breast cancer who were ineligible for bisphosphonate therapy and stayed on treatment for 1 year (N = 232). Serum 25(OH)D was measured at baseline and 3 months, and lumbar spine (LS) bone mineral density at baseline and 1 year. Subjects were supplemented with daily calcium (1 g) and vitamin D(3) (800 IU) and additional oral 16,000 IU every 2 weeks if baseline 25(OH)D was <30 ng/ml. Linear regression models were fitted to adjust for potential confounders. After 1 year on AI therapy, 232 participants experienced a significant 1.68 % [95 % CI 1.15-2.20 %] bone loss at LS (0.017 g/cm(2) [0.012-0.024], P < 0.0001). Higher 25(OH)D at 3 months protected against LS bone loss (-0.5 % per 10 ng/ml [95 % CI -0.7 to -0.3 %], adjusted P = 0.0001), and those who reached levels ≥40 ng/ml had reduced bone loss by 1.70 % [95 % CI 0.4-3.0 %; adjusted P = 0.005] compared to those with low 25(OH)D levels (<30 ng/ml). We conclude that improved vitamin D status using supplementation is associated with attenuation of AI-associated bone loss. For this population, the current Institute of Medicine target recommendation of 20 ng/ml might be too low to ensure good bone health.

Serum 25-hydroxyvitamin D levels among Boston trainee doctors in winter

As indoor workers, trainee doctors may be at risk for inadequate vitamin D. All trainee doctors (residents) in a Boston pediatric training program (residency) were invited to complete a survey, and undergo testing for serum 25-hydroxyvitamin D [25(OH)D], PTH, and calcium during a 3-week period in March 2010. We examined the association between resident characteristics and serum 25(OH)D using Chi2 and Kruskal-Wallis test and multivariable linear and logistic regression. Of the 119 residents, 102 (86%) participated. Although the mean serum 25(OH)D level was 67 nmol/L (±26), 25 (25%) had a level <50 nmol/L and 3 (3%) residents had levels <25 nmol/L. In the multivariable model, factors associated with 25(OH)D levels were: female sex (β 12.7, 95% CI 3.6, 21.7), white race (β 21.7, 95% CI 11.7, 31.7), travel to more equatorial latitudes during the past 3 months (β 6.3, 95% CI 2.0, 10.5) and higher daily intake of vitamin D (β 1.1, 95% CI 0.04, 2.1). Although one in four residents in our study had a serum 25(OH)D <50 nmol/L, all of them would have been missed using current Centers for Medicare and Medicaid Services (CMS) screening guidelines. The use of traditional risk factors appears insufficient to identify low vitamin D in indoor workers at northern latitudes.

25-Hydroxy vitamin-D, obesity, and associated variables as predictors of breast cancer risk and tamoxifen benefit in NSABP-P1

Observational studies suggest that host factors are associated with breast cancer risk. The influence of obesity, vitamin-D status, insulin resistance, inflammation, and elevated adipocytokines in women at high risk of breast cancer is unknown. The NSABP-P1 trial population was used for a nested case–control study. Cases were drawn from those who developed invasive breast cancer and controls selected from unaffected participants (≤4 per case) matched for age, race, 5 year Gail score, and geographic location of clinical center as a surrogate for latitude. Fasting serum banked at trial enrolment was assayed for 25-hydroxy vitamin-D (25OHD), insulin, leptin (adipocytokine), and C-reactive protein (CRP, marker of inflammation). Logistic regression was used to test for associations between study variables and the risk of invasive breast cancer. Two hundred and thirty-one cases were matched with 856 controls. Mean age was 54, and 49% were premenopausal. There were negative correlations for 25OHD with body mass index (BMI), insulin, CRP, and leptin. BMI ≥ 25 kg/m² was associated with higher breast cancer risk (odds ratio [OR] 1.45, p = 0.02) and tamoxifen treatment was associated with lower risk (OR = 0.44, p < 0.001). Suboptimal 25OHD (<72 nmol/l) did not influence breast cancer risk (OR = 1.06, p = 0.76). When evaluated as continuous variables, 25OHD, insulin, CRP, and leptin levels were not associated with breast cancer risk (all p > 0.34). In this high risk population, higher BMI was associated with a greater breast cancer risk. Serum levels of 25OHD, insulin, CRP, and leptin were not independent predictors of either breast cancer risk or tamoxifen benefit.

Vitamin D status: a review with implications for the pelvic floor

Vitamin D is a micronutrient vital in calcium homeostasis and musculoskeletal function. Vitamin D insufficiency is a common variant of vitamin D deficiency that shows clinical signs of rickets and osteomalacia. The clinical significance of vitamin D insufficiency is being explored in several medical conditions. However, the most robust work suggests a role in musculoskeletal disease. The pelvic floor is a unique part of the body and the function of which is dependent on interrelationships between muscle, nerve, connective tissue, and bone. Pelvic floor disorders result when these relationships are disrupted. This paper reviews current knowledge regarding vitamin D nutritional status, the importance of vitamin D in muscle function, and how insufficient or deficient vitamin D levels may play a role in the function of the female pelvic floor.

Secondary fracture prevention

Osteoporosis causes no symptoms until there is a fracture. Although screening for osteoporosis is recommended for some populations, patients may present with a fragility fracture. Such patients are at high risk for subsequent fractures. Despite this high risk and the presence of generally safe and effective osteoporosis therapy, only a minority of low trauma fracture patients have evaluation and treatment of underlying osteoporosis. A brief summary of the evaluation and medical treatment of the post-fracture patient is provided. Several institutions, integrated health systems, and countries have instituted programs to identify, evaluate, and treat fragility fracture patients. Such programs have had variable success. This article describes some of the programs that work, their cost-effectiveness, and the applicability to the generally non-integrated US health care system. It is clear that better management of the post-fracture patient (and other high-risk patients) will lead to fewer fractures, decreased morbidity and mortality, and long-term cost savings.

An update on vitamin D and human immunity

In the last 5 years, there has been a remarkable change in our understanding of the health benefits of vitamin D. The classical actions of vitamin D as a determinant of mineral metabolism and rachitic bone disease have been expanded to include a broader role in skeletal homoeostasis and prevalent bone disorders such as osteoporosis. However, it is the nonskeletal function of vitamin D that has attracted most attention. Although pluripotent responses to vitamin D have been recognized for many years, our new perspective on nonclassical vitamin D function stems from two more recent concepts. The first is that impaired, vitamin D status is common to many populations across the globe. This has prompted studies to explore the health impact of suboptimal circulating levels of vitamin D, with association studies linking vitamin D 'insufficiency' to several chronic health problems including autoimmune and cardiovascular disease, hypertension and common cancers. In support of a broader role for vitamin D in human health, studies in vitro and using animal models have highlighted immunomodulatory and anticancer effects of vitamin D that appear to depend on localized activation of vitamin D. The conclusion from these reports is that many nonclassical actions of vitamin D are independent of conventional vitamin D endocrinology and are therefore more sensitive to variations in vitamin D status. The current review summarizes these developments, with specific reference to the newly identified effects of vitamin D on the immune system, but also highlights the challenges in translating these observations to clinical practice.

Low serum vitamin D is associated with increased mortality in elderly men: MrOS Sweden

In elderly man, low serum 25-hydroxyvitamin D (25(OH)D) was associated with a substantial excess risk of death compared to 25(OH)D values greater than 50-70 nmol/l, but the association attenuated with time.

INTRODUCTION

The aim of the present study was to determine whether poor vitamin D status was associated with an increase in the risk of death in elderly men.

METHODS

We studied the relationship between serum 25(OH)D and the risk of death in 2,878 elderly men drawn from the population and recruited to the MrOS study in Sweden. Baseline data included general health and lifestyle measures and serum 25(OH)D measured by competitive RIA. Men were followed for up to 8.2 years (average 6.0 years).

RESULTS

Mortality adjusted for comorbidities decreased by 5% for each SD increase in 25(OH)D overall (gradient of risk 1.05; 95% confidence interval 0.96-1.14). The predictive value of 25(OH)D for death was greatest below a threshold value of 50-70 nmol/l, was greatest at approximately 3 years after baseline and thereafter decreased with time.

CONCLUSIONS

Low serum 25(OH)D is associated with a substantial excess risk of death compared to 25(OH)D values greater than 50-70 nmol/l, but the association attenuates with time. These findings, if causally related, have important implications for intervention in elderly men.

Determinants of vitamin D status in a general population of Danish adults

BACKGROUND AND AIMS

Danish legislation regarding food fortification has been very restrictive and vitamin D deficiency is thought to be common in Denmark due to inadequate dietary intakes and the fact that in Denmark (latitude 56°N) vitamin D is only synthesized in the skin after exposure to solar radiation during summertime (April-September). The purpose of this study was to evaluate the vitamin D status of a general adult population in Denmark and, in addition, associations between vitamin D status and distinct lifestyle factors were studied.

METHODS

A random sample of 6784 persons from a general population aged 30-60 years participated in a health examination in 1999-2001. Serum samples from all participants were stored and levels of 25-hydroxyvitamin D (25(OH)D) were measured by HPLC in 2009. The method was compared to another HPLC method. Information on dietary intake of vitamin D and other lifestyle factors were obtained by questionnaires. A total of 6146 persons defined as ethnic Danes and with successful measurements of 25(OH)D were included in the analyses.

RESULTS

The overall prevalence of vitamin D deficiency (25(OH)D<25 nmol/l) and insufficiency (25(OH)D<50 nmol/l) were 13.8% and 52.2%, respectively. A marked seasonal fluctuation was seen in serum levels of 25(OH)D - median values of 25(OH)D were lowest in February and highest in August. In multiple logistic regression models (n=5506), low vitamin D status was significantly associated with obesity (BMI≥30), daily smoking and a sedentary lifestyle. However, measurements of 25(OH)D were not associated with the estimated dietary intake of vitamin D. Comparison of two HPLC methods demonstrated considerable differences in accuracy.

DISCUSSION AND CONCLUSIONS

Our results suggest that poor vitamin D status is common among adults in a Northern European country without food fortification with vitamin D. Methodological issues are, however, of great importance when using cut-off values to define poor vitamin D status. In addition, we demonstrated that low serum levels of 25(OH)D were associated with several lifestyle factors.

Plasma 25-hydroxyvitamin D and progression to diabetes in patients at risk for diabetes: an ancillary analysis in the Diabetes Prevention Program

OBJECTIVE

To investigate the association between vitamin D status, assessed by plasma 25-hydroxyvitamin D, and risk of incident diabetes.

RESEARCH DESIGN AND METHODS

Prospective observational study with a mean follow-up of 2.7 years in the Diabetes Prevention Program (DPP), a multicenter trial comparing different strategies for prevention of diabetes in patients with prediabetes. We assessed the association between plasma 25-hydroxyvitamin D, measured repeatedly during follow-up, and incident diabetes in the combined placebo (n = 1,022) and intensive lifestyle (n = 1,017) randomized arms of the DPP. Variables measured at multiple study time points (25-hydroxyvitamin D, BMI, and physical activity) entered the analyses as time-varying "lagged" covariates, as the mean of the previous and current visits at which diabetes status was assessed.

RESULTS

After multivariate adjustment, including for the DPP intervention, participants in the highest tertile of 25-hydroxyvitamin D (median concentration, 30.1 ng/mL) had a hazard ratio of 0.72 (95% CI 0.56-0.90) for developing diabetes compared with participants in the lowest tertile (median concentration, 12.8 ng/mL). The association was in the same direction in placebo (0.70; 0.52-0.94) versus lifestyle arm (0.80; 0.54-1.17).

CONCLUSIONS

Higher plasma 25-hydroxyvitamin D, assessed repeatedly, was associated with lower risk of incident diabetes in high-risk patients, after adjusting for lifestyle interventions (dietary changes, increased physical activity, and weight loss) known to decrease diabetes risk. Because of the observational nature of the study, the potential association between vitamin D and diabetes needs to be confirmed in intervention studies.

Vitamin D supplementation: guidelines and evidence for subclinical deficiency

PURPOSE OF REVIEW

To summarize recommendations from the 2011 US Institute of Medicine report (on vitamin D) and the new guideline from the US Endocrine Society with emphasis on treating and preventing vitamin D deficiency, including patients with inflammatory bowel disease and prior gastric bypass.

RECENT FINDINGS

The US Institute of Medicine Recommended Dietary Allowance of vitamin D is 400 IU per day for children younger than 1 year of age, 600 IU per day for children at least 1 year of age and adults up to 70 years, and 800 IU per day for older adults. The US Institute of Medicine concluded that serum 25-hydroxyvitamin D [25(OH)D] of 20 ng/ml or more will cover the requirements of 97.5% of the population. The US Endocrine Society's Clinical Practice Guideline suggested that 400-1000 IU per day may be needed for children aged less than 1 year, 600-1000 IU per day for children aged 1 year or more, and 1500-2000 IU per day for adults aged 19 years or more to maintain 25(OH)D above the optimal level of 30 ng/ml. Patients with inflammatory bowel disease even in a quiescent state and those with gastric bypass malabsorb vitamin D and need more vitamin D to sustain their vitamin D status.

SUMMARY

Difference in the recommendations from the US Institute of Medicine and the US Endocrine Society's Practice Guideline reflects different goals and views on current evidence. Significant gaps remain in the literature, and studies of vitamin D treatment assessing changes in outcomes at different 25(OH)D levels are needed.

Rickets-vitamin D deficiency and dependency

Rickets is an important problem even in countries with adequate sun exposure. The causes of rickets/osteomalacia are varied and include nutritional deficiency, especially poor dietary intake of vitamin D and calcium. Non-nutritional causes include hypophosphatemic rickets primarily due to renal phosphate losses and rickets due to renal tubular acidosis. In addition, some varieties are due to inherited defects in vitamin D metabolism and are called vitamin D dependent rickets. This chapter highlights rickets/osteomalacia related to vitamin D deficiency or to inherited defects in vitamin D metabolism. Hypophosphatemic rickets and rickets due to renal tubular acidosis are discussed in other sections of the journal.

Vitamin D in the new millennium

The incidence of vitamin D deficiency is rising worldwide, yet in the vast majority of patients, the condition remains undiagnosed and untreated. Current evidence overwhelmingly indicates that supplemental doses greater than 800 IU/day have beneficial effects on the musculoskeletal system, improving skeletal homeostasis, thus leading to fewer falls and fractures. Evidence is also accumulating on the beneficial effects of vitamin D on extraskeletal systems, such as improving immune health, autoimmune disorders, cancer, neuromodulation, diabetes, and metabolic syndrome. The cause-effect relationship of vitamin D deficiency with increasing incidences of nonskeletal disorders is being investigated. Published reports support the definition of sufficiency, serum levels of 25-hydroxyvitamin D [25(OH)D] greater than 30 ng/mL (75 nmol/L). To achieve this, most people need vitamin D supplementation ranging from 600 to 2000 IU/day; consumption up to of 5000 international units (IU) per day of vitamin D is reported as safe. Although light-skinned individuals need 1000 IU/day of vitamin D, elderly and dark-skinned individuals are likely to need approximately 2000 IU/day to maintain serum 25(OH)D levels greater than 30 ng/mL. Other vulnerable patients, such as the obese, those who have undergone bariatric surgery, and those with gastrointestinal malabsorption syndromes, may require higher doses of vitamin D to maintain normal serum levels and be healthy.

25-hydroxyvitamin D assay variations and impact on clinical decision making

CONTEXT

Laboratories are increasingly shifting to new automated 25-hydroxyvitamin D (25-OHD) assays, with subsequent variability in results.

OBJECTIVE/SETTING

We describe the experience at our center with such a shift and illustrate its clinical implications.

METHODS

25-OHD levels were measured in 494 patients using Immunodiagnostic Systems RIA (IDS-RIA) and DiaSorin Liaison assays. Sources of variability between the assays were investigated in a subset of 83 samples, retested in the reference laboratory in the United States, and by reviewing the performance reports issued by the International Vitamin D External Quality Assessment Scheme, DEQAS. 25-OHD cut-points for target levels were used to compare the two assays.

RESULTS

25-OHD concentrations were significantly lower when measured with Liaison as compared to IDS-RIA: mean bias was -5 ng/ml, range was -38.1 to 18.7 ng/ml, P<0.001; the absolute bias was independent of 25-OHD value. Interassay variability was also detected in values obtained in the reference laboratory and in DEQAS reports. Using 20 ng/ml as the target 25-OHD level, 52% of patients required treatment when tested by Liaison, as opposed to 36% by IDS-RIA (P<0.001). Using 30 ng/ml as the desirable level, the proportions were 79 and 64%, respectively (P<0.001). The two assays agreed in only 41-68% of subjects, proportions that depended on criteria used to define agreement.

CONCLUSION

A change in 25-OHD assays has a significant impact on results, patient classification, and treatment recommendations. Such variability cannot be ignored when deriving and applying vitamin D guidelines. It also renders universal assay standardization a pressing call.

Vitamin D metabolism and signaling in the immune system

Vitamin D has emerged as a pleiotropic regulator of human physiology, and recent work has revealed that it has several roles in control of human immune system function. Vitamin D was originally characterized for its role in calcium homeostasis, and the active form, 1,25-dihydroxyvitamin D (1,25D), can be produced in the kidney by 1α-hydroxylation of circulating 25-hydroxyvitamin D catalyzed by the enzyme CYP27B1. Renal CYP27B1 expression is regulated by calcium regulatory inputs, and 1,25D produced in the kidney was thought to function largely as an endocrine hormone. However, it is now clear that CYP27B1 is expressed in numerous tissues, and that 1,25D acts at several sites in the body in an intracrine or paracrine manner. In particular, both CYP27B1 and the vitamin D receptor (VDR) are expressed in several cell types in the immune system, where CYP27B1 production is controlled by a number of immune-specific inputs. Recent research has opened several windows on the molecular mechanisms by which 1,25D signaling regulates both innate and adaptive immune responses in humans. Moreover, intervention trials are beginning to provide evidence that vitamin D supplementation can bolster clinical responses to infection. This review will discuss recent developments in our understanding of how immune signaling controls local vitamin D metabolism and how, in turn, the 1,25D-bound VDR modulates immune system function. A particular emphasis will be placed on the interplay between vitamin D signaling and signaling through different classes of pattern recognition receptors in the production of antimicrobial peptides during innate immune responses to microbial infection.

Does vitamin D protect against DNA damage?

Vitamin D is a secosteroid best known for its role in maintaining bone and muscle health. Adequate levels of vitamin D may also be beneficial in maintaining DNA integrity. This role of vitamin D can be divided into a primary function that prevents damage from DNA and a secondary function that regulates the growth rate of cells. The potential for vitamin D to reduce oxidative damage to DNA in a human has been suggested by clinical trial where vitamin D supplementation reduced 8-hydroxy-2'-deoxyguanosine, a marker of oxidative damage, in colorectal epithelial crypt cells. Studies in animal models and in different cell types have also shown marked reduction in oxidative stress damage and chromosomal aberrations, prevention of telomere shortening and inhibition of telomerase activity following treatment with vitamin D. The secondary function of vitamin D in preventing DNA damage includes regulation of the poly-ADP-ribose polymerase activity in the DNA damage response pathway involved in the detection of DNA lesions. It is also able to regulate the cell cycle to prevent the propagation of damaged DNA, and to regulate apoptosis to promote cell death. Vitamin D may contribute to prevention of human colorectal cancer, though there is little evidence to suggest that prevention of DNA damage mediates this effect, if real. Very limited human data mean that the intake of vitamin D required to minimise DNA damage remains uncertain.

Current recommendations for laboratory testing and use of bone turnover markers in management of osteoporosis

Osteoporosis is a major health problem worldwide, and is projected to increase exponentially due to the aging of the population. The absolute fracture risk in individual subjects is calculated by the use of algorithms which include bone mineral density (BMD), age, gender, history of prior fracture and other risk factors. This review describes the laboratory investigations into osteoporosis which include serum calcium, phosphate, creatinine, alkaline phosphatase and 25-hydroxyvitamin D and, additionally in men, testosterone. Parathyroid hormone (PTH) is measured in patients with abnormal serum calcium to determine its cause. Other laboratory investigations such as thyroid function testing, screening for multiple myeloma, and screening for Cushing's syndrome, are performed if indicated. Measurement of bone turnover markers (BTMs) is currently not included in algorithms for fracture risk calculations due to the lack of data. However, BTMs may be useful for monitoring osteoporosis treatment. Further studies of the reference BTMs serum carboxy terminal telopeptide of collagen type I (s-CTX) and serum procollagen type I N-terminal propeptide (s-PINP) in fracture risk prediction and in monitoring various treatments for osteoporosis may help expedite their inclusion in routine clinical practice.

Calcium and vitamin D controversies

Controversies regarding appropriate use of vitamin D and calcium are predominately related to the extraskeletal effects. Calcium and vitamin D are essential for bone health. The concerns regarding calcium and cardiovascular complications are inconclusive at best, and do not warrant a change in our approach to supplementation at this time. A growing body of literature exists suggesting that additional vitamin D may have numerous benefits, although more study needs to be done. Further prospective trials would provide insight into the potential advantages that increased vitamin D supplementation could provide.

Aromatase inhibitors and calcium absorption in early stage breast cancer

To investigate the effect of aromatase inhibitors (AI) on intestinal calcium absorption, measured using the gold-standard dual stable calcium isotope method. In this pilot study, we recruited 10 postmenopausal women with hormone receptor-positive breast cancer who planned to initiate AI therapy; women receiving chemotherapy were excluded. Women completed two 24 h inpatient calcium absorption study visits, the first prior to AI therapy and the second at least 6 weeks following onset of AI therapy. We calculated total fractional calcium absorption (TFCA) using the dose-corrected fractional recovery of two stable isotopes from 24 h urine collections. Ten postmenopausal women (mean±SD age, 66±7 years; 25(OH)D 40±7 ng/mL, and total calcium intake of 1,714±640 mg/day) exhibited no change in TFCA related to AI therapy (0.155±0.042 prior to and 0.160±0.064 following AI therapy, p=1.0). Subjects exhibited a surprisingly small decline in serum estradiol levels with AI therapy that was not statistically significant. However, there was a significant correlation between duration of AI therapy and the decline in serum estradiol levels (r=-0.65, p=0.040). In this pilot study, AI therapy did not decrease TFCA. Women with early stage breast cancer exhibited an unexpectedly low TFCA, most likely due to their high calcium intake. The null effect of AI therapy on TFCA might relate to the brief duration of AI therapy, the minimal effect of AI therapy on estradiol levels, subjects' high calcium intake or excellent vitamin D status.

Suboptimal magnesium status in the United States: are the health consequences underestimated?

In comparison with calcium, magnesium is an "orphan nutrient" that has been studied considerably less heavily. Low magnesium intakes and blood levels have been associated with type 2 diabetes, metabolic syndrome, elevated C-reactive protein, hypertension, atherosclerotic vascular disease, sudden cardiac death, osteoporosis, migraine headache, asthma, and colon cancer. Almost half (48%) of the US population consumed less than the required amount of magnesium from food in 2005-2006, and the figure was down from 56% in 2001-2002. Surveys conducted over 30 years indicate rising calcium-to-magnesium food-intake ratios among adults and the elderly in the United States, excluding intake from supplements, which favor calcium over magnesium. The prevalence and incidence of type 2 diabetes in the United States increased sharply between 1994 and 2001 as the ratio of calcium-to-magnesium intake from food rose from <3.0 to >3.0. Dietary Reference Intakes determined by balance studies may be misleading if subjects have chronic latent magnesium deficiency but are assumed to be healthy. Cellular magnesium deficit, perhaps involving TRPM6/7 channels, elicits calcium-activated inflammatory cascades independent of injury or pathogens. Refining the magnesium requirements and understanding how low magnesium status and rising calcium-to-magnesium ratios influence the incidence of type 2 diabetes, metabolic syndrome, osteoporosis, and other inflammation-related disorders are research priorities.

High prevalence of vitamin D deficiency among children aged 1 month to 16 years in Hangzhou, China

BACKGROUND

Recent studies have suggested that vitamin D deficiency in children is widespread. But the vitamin D status of Chinese children is seldom investigated. The objective of the present study was to survey the serum levels of 25-hydroxyvitamin D [25(OH)D] in more than 6,000 children aged 1 month to 16 years in Hangzhou (latitude: 30°N), the capital of Zhejiang Province, southeast China.

METHODS

The children aged 1 month to 16 years who came to the child health care department of our hospital, the children's hospital affiliated to Zhejiang university school of medicine, for health examination were taken blood for 25(OH) D measurement. Serum 25(OH) D levels were determined by direct enzyme-linked immunosorbent assay and categorized as < 25, < 50, and < 75 nmol/L.

RESULTS

A total of 6,008 children aged 1 month to 16 years participated in this cross-sectional study. All the subjects were divided into subgroups according to their age: 0-1y, 2-5y, 6-11y and 12-16y representing infancy, preschool, school age and adolescence stages respectively. The highest mean level of serum 25(OH)D was found in the 0-1y stage (99 nmol/L) and the lowest one was found in 12-16y stage (52 nmol/L). Accordingly, the prevalence of serum 25(OH)D levels of < 75 nmol/L and < 50 nmol/L were at the lowest among infants (33.6% and 5.4% respectively) and rose to the highest among adolescents (89.6% and 46.4% respectively). The mean levels of serum 25(OH)D and the prevalence of vitamin D deficiency changed according to seasons. In winter and spring, more than 50% of school age children and adolescents had a 25(OH)D level at < 50 nmol/L. If the threshold is changed to < 75 nmol/L, all of the adolescents (100%) had low 25(OH)D levels in winter and 93.7% school age children as well.

CONCLUSIONS

The prevalence of vitamin D deficiency and insufficiency among children in Hangzhou Zhejiang province is high, especially among children aged 6-16 years. We suggest that the recommendation for vitamin D supplementation in Chinese children should be extended to adolescence.

Vitamin D and osteoporosis-related fracture

The age-related decline in mass and quality of bone (osteoporosis) and muscle (sarcopenia) leads to an exponential increased risk for osteoporosis-related fracture with advancing age in older adults. As vitamin D inadequacy plausibly causally contributes to these declines, optimization of vitamin D status might reduce the deterioration of bone and muscle function with age. Putative mechanisms by which vitamin D inadequacy may increase fracture risk include both direct and indirect effects on bone and muscle. However, controversy currently clouds the role(s) of vitamin D in osteoporosis-related fracture, the amount of vitamin D required and the optimal 25-hydroxyvitamin D level. This review provides an overview of current knowledge and suggests a clinical approach to vitamin D status in older adults with, or at risk for, osteoporosis-related fracture. These recommendations are likely to evolve as additional data becomes available.

Steroid requirements and immune associations with vitamin D are stronger in children than adults with asthma

BACKGROUND

The effects of serum vitamin D status on atopy, steroid requirement, and functional responsiveness to corticosteroids in children versus adults with asthma have not been studied systematically.

OBJECTIVE

We sought to explore the age-specific effects of vitamin D in asthmatic patients.

METHODS

Serum vitamin D levels were examined in a prospective study of adults and children (102 healthy control subjects and 103 asthmatic patients). PBMCs were cultured for 3 hours with or without 100 nmol/L dexamethasone, and the expression of corticosteroid-regulated genes was detected by using real-time PCR. Serum IgE levels were measured, and information about asthmatic patients' steroid requirements was collected.

RESULTS

Deficient serum vitamin D levels (<20 ng/mL) were found in 47.6% of asthmatic patients and 56.8% of healthy control subjects, with means ± SDs of 20.7 ± 9.8 and 19.2 ± 7.7 ng/mL, respectively. In multivariate regression models a significant positive correlation between serum vitamin D levels and the expression of vitamin D-regulated targets, cytochrome P450, family 24, subfamily a (cyp24a) expression by PBMCs (P = .0084, pediatric asthma group only) and serum LL-37 levels (P = .0006 in the pediatric group but P = .0067 in the adult asthma group), was found. An inverse association between vitamin D and serum IgE levels was observed in the pediatric (P = .006) asthma group. Serum vitamin D level (P = .05), as well as PBMC cyp24a expression (P = .0312), demonstrated a significant inverse relationship with daily inhaled corticosteroid dose in the pediatric asthma group only. Cyp24a expression in PBMCs correlated positively with in vitro suppression of TNF-α by dexamethasone (P = .05) and IL-13 (P = .0094) in PBMCs in the pediatric asthma group only.

CONCLUSIONS

This study demonstrated significant associations between serum vitamin D status and steroid requirement and in vitro responsiveness to corticosteroids in the pediatric but not the adult asthma group. Vitamin D was also related to IgE levels in children but not in adults.

Vitamin D in relation to myocardial structure and function after eight years of follow-up: the Hoorn study

BACKGROUND AND AIMS

To investigate associations between baseline serum 25-hydroxyvitamin D [25(OH)D] levels and myocardial structure and function after 8 years of follow-up in older Dutch subjects.

METHODS

We included 256 subjects of the Hoorn Study, a population-based cohort. They underwent a standardized 2-dimensional echocardiogram at baseline between 2000 and 2001, and again between 2007 and 2009. We studied the association of 25(OH)D quartiles with echocardiographic measures of the left ventricular mass index (LVMI), left ventricular systolic function and markers of diastolic function using linear regression analyses.

RESULTS

At baseline, subjects had a mean age of 67.4 ± 5.2 years and 41.4% had prior cardiovascular disease (CVD). Low serum 25(OH)D levels were only associated with higher LVMI at 8-year follow-up in subjects without prior CVD and in subjects with low kidney function (median estimated glomerular filtration rate ≤77.5 ml/min/1.73m(2)). The associations attenuated after adjustments for parathyroid hormone (PTH), which was associated with higher LVMI (g/m(2.7)) in subjects with low kidney function (regression coefficient highest quartile 6.3, 95% CI: 0.2, 12.5).

CONCLUSION

This study showed no strong associations of 25(OH)D with myocardial structure and function. However, PTH - a possible modifiable mediator in the relation between 25(OH)D and myocardial structure - was positively associated with LVMI in subjects with low kidney function.

Vitamin D deficiency is a predictor of reduced survival in patients with heart failure; vitamin D supplementation improves outcome

AIMS

Vitamin D deficiency is a highly prevalent, global phenomenon. The prevalence in heart failure (HF) patients and its effect on outcome are less clear. We evaluated vitamin D levels and vitamin D supplementation in patients with HF and its effect on mortality.

METHODS AND RESULTS

25-Hydroxyvitamin D [25(OH)D] levels were evaluated in HF patients from a health maintenance organization (HMO), and compared them with those of the rest of the members of the HMO. Patients with HF (n = 3009) had a lower median 25(OH)D level compared with the control group (n = 46 825): 36.9 nmol/L (interquartile range 23.2-55.9) vs. 40.7 nmol/L (26.7-56.9), respectively, P < 0.00001. The percentage of patients with vitamin D deficiency [25(OH)D <25 nmol/L] was higher in patients with HF compared with the control group (28% vs. 22%, P < 0.00001). Only 8.8% of the HF patients had optimal 25(OH)D levels (≥75 nmol/L). Median clinical follow-up was 518 days. Cox regression analysis demonstrated that vitamin D deficiency was an independent predictor of increased mortality in patients with HF [hazard ratio (HR) 1.52, 95% confidence interval (CI) 1.21-1.92, P < 0.001] and in the control group (HR 1.91, 95% CI 1.48-2.46, P < 0.00001). Vitamin D supplementation was independently associated with reduced mortality in HF patients (HR 0.68, 95% CI 0.54-0.85, P < 0.0001). Parameters associated with vitamin D deficiency in HF patients were decreased previous solar radiation exposure, body mass index, diabetes, female gender, pulse, and decreased calcium and haemoglobin levels.

CONCLUSIONS

Vitamin D deficiency is highly prevalent in HF patients and is a significant predictor of reduced survival. Vitamin D supplementation was associated with improved outcome.

Vitamin D, osteocalcin, and risk for adiposity as comorbidities in middle school children

Nonclassic actions of vitamin D include potential regulation of immune function and glucose homeostasis. The bone-metabolism loop has recently been expanded to include osteocalcin, which appears to play a more direct role in pancreatic beta cell function and energy metabolism. We hypothesized that both vitamin D and osteocalcin would correlate negatively with indices of adiposity-related comorbidity risk in periadolescents, varying by ethnic group. We analyzed anthropometric, metabolic, and inflammatory markers from a multiethnic population of 106 school children 11 to 14 years of age studied as part of the Reduce Obesity and Diabetes (ROAD) consortium. As expected, 25-hydroxyvitamin D (25-OH vitamin D) was inversely correlated with intact parathyroid hormone (iPTH); total osteocalcin (OCN) and uncarboxylated osteocalcin (uOCN) were directly correlated with each other. OCN and uOCN concentrations correlated inversely with age. Vitamin D deficiency was most prevalent among East Asians (EA) and African Americans (AA). The highest lipid risk scores and homeostatic model for assessment of insulin resistance (HOMA-IR) values were seen in the South Asian (SA) group. Overall, adiposity measures were inversely correlated with OCN and iPTH, whereas such relationships were not observed for vitamin D. Acute insulin response to glucose challenge correlated negatively with uOCN in all subjects; however, lipid risk score correlated negatively with uOCN only in whites. The relationships between markers of calcium metabolism and body composition, glucose homeostasis, lipids, and inflammation all showed racial and ethnic differences. No consistent relationship was found between vitamin D and adiposity or vitamin D and glucose metabolism; instead vitamin D levels varied by race and ethnicity in this school-based group. These findings are consistent with the hypothesis that markers of calcium and bone metabolism may reflect risk for adiposity-related comorbidities in children.