Determinants of vitamin D status among overweight and obese Puerto Rican adults

Association between serum vitamin D level and cardiovascular disease in Chinese patients with type 2 diabetes mellitus: a cross-sectional study

The relationship between 25-hydroxyvitamin D (25(OH)D) status and cardiovascular disease (CVD) in the diabetes population still needs to be clarified. This study aimed to explore the association of 25(OH)D with CVD and cardiometabolic risk factors in Chinese population with type 2 diabetes mellitus (T2DM). This cross-sectional study was performed with 1378 hospitalized patients with T2DM. Participants were classified into three groups according to the serum 25(OH)D levels: vitamin D adequate, vitamin D insufficiency and vitamin D deficient. Multivariate logistic regression analysis, stratified analysis and interaction analysis were performed to determine the relationship between serum 25(OH)D levels and CVD outcome. After adjusting for confounders, serum 25(OH)D levels were significantly negatively associated with cardiovascular disease in type 2 diabetic patients [OR: 0.97 (0.94, 0.99), p = 0.0131]. Taking the vitamin D-sufficient group (≥ 20 ng/mL) as a reference, the vitamin D-deficiency group (< 12 ng/mL) was associated with a significantly higher risk of cardiovascular disease, with a 1.25-fold increased risk after adjusting for all potential confounders [OR: 2.25 (1.33, 3.79), p = 0.0023]. Stratification analysis showed that the association between vitamin D deficiency and increased risk of cardiovascular disease was particularly significant in women [OR: 4.32 (1.54, 12.12), p = 0.0055], older adults [OR: 4.14 (1.10, 15.56), p = 0.0355], normal-weight [OR: 4.09 (1.51, 11.10), p = 0.0056] and obese subjects [OR: 3.66 (1.03, 13.05), p = 0.0453]. Vitamin D deficiency was significantly associated with an increased risk of overweight/obesity [OR: 1.57 (1.10, 2.24), p = 0.0134], hypertension [OR: 1.81 (1.30, 2.51), p = 0.0004], hypertriglyceridemia [OR: 1.56 (1.12, 2.16), p = 0.0078] and reduced HDL-C [OR: 1.67 (1.19, 2.35), p = 0.0033]. Serum 25(OH)D levels were significantly negatively associated with CVD in T2DM patients and vitamin D deficiency was significantly associated with an increased risk of overweight/obesity, hypertension and dyslipidemia.

Vitamin D Enhancement of Adipose Biology: Implications on Obesity-Associated Cardiometabolic Diseases

Vitamin D is activated into 1α,25(OH)2D through two hydroxylation steps that are primarily catalyzed by 25-hydroxylase in the liver and 1α-hydroxylase in the kidneys. The active form of vitamin D regulates myriads of cellular functions through its nuclear receptor, vitamin D receptor (VDR). Vitamin D metabolizing enzymes and VDR are expressed in adipose tissues and vitamin D regulates multiple aspects of adipose biology including the recruitment and differentiation of adipose stem cells into adipocytes and metabolic, endocrine, and immune properties. Obesity is associated with low vitamin D status, which is thought to be explained by its sequestration in large mass of adipose tissues as well as dysregulated vitamin D metabolism. Low vitamin D status in obesity may negatively impact adipose biology leading to adipose tissue dysfunctions, the major pathological factors for cardiometabolic diseases in obesity. In this review, the current understanding of vitamin D metabolism and its molecular mechanisms of actions, focusing on vitamin D-VDR regulation of adipose biology with their implications on obesity-associated diseases, is discussed. Whether improving vitamin D status leads to reductions in adiposity and risks for cardiometabolic diseases is also discussed.

Vitamin D and obesity

An inverse association between vitamin D status and obesity has been reported across diverse populations and age groups in humans. In animal model of diet-induced obesity, dysregulation of vitamin D metabolism has been observed. However, the causal relationship between vitamin D status and obesity is not conclusive. Several explanations, such as volumetric dilution, sequestration of vitamin D into adipose tissue, and limited sunlight exposure, have been suggested as the underlying mechanisms linking poor vitamin D status and obesity. Vitamin D can modulate adipose tissue biology, spanning from adipocyte differentiation to adipocyte apoptosis and energy metabolism, indicating its potential impact on adiposity. In this chapter, we will review the prevalence of vitamin D deficiency and determinants of vitamin D deficiency among different populations, as well as changes in vitamin D metabolism associated with obesity. Additionally, we will review vitamin D's regulation of adipogenesis and lipogenesis at the cellular level in order to gain a deeper understanding of the underlying mechanisms linking vitamin D levels and obesity.

The Association of Obesity and the Antiaging Humoral Factor Klotho in Middle-Aged and Older Adults

Objectives

Previous studies have reported conflicting results regarding the relationship between obesity and the antiaging humoral factor klotho. Thus, the present study aimed to examine the association of anthropometric measurements, weight history change, and vitamin D status with serum klotho levels.

Methods

The National Health and Nutrition Examination Survey data were used to compare sex-specific logarithm transformed serum klotho levels across standardized anthropometric measurements and weight change history in subjects aged 40-79 years. The baseline measured height, and self-reported weight were used to calculate the body mass index (BMI) at two-time intervals: age 25 and ten years before the measured BMI. Subjects were then categorized as never obese, obese to nonobese, nonobese to obese, and always obese.

Results

Of 4,971 participants, the prevalence of general obesity was 41%, and abdominal obesity (waist circumference ≥88 cm) was present in 75% of women. Overall, lower serum klotho levels were seen in older adults, men, nonsmokers, alcohol users, and those with an estimated glomerular filtration rate (eGFR) < 60 ml/min. Multivariate models demonstrated that general and abdominal obesity in women was inversely associated with serum klotho levels. Moreover, women who developed obesity from age 25 and ten years before the baseline BMI had significantly lower mean klotho levels at 765.0 and 757.4 pg/ml compared with 820.5 pg/ml (p < 0.05) among those that were never obese, respectively. In contrast, serum klotho levels did not significantly differ among men, irrespective of their weight history. In a subanalysis, higher klotho levels were seen in participants with an adequate vitamin D status (≥50 nmol/L) than their overweight and obese counterparts (p < 0.05).

Conclusions

Obesity among women was significantly and inversely associated with serum klotho levels. Similarly, women who developed obesity during their lifetime had consistently lower klotho levels than their never-obese counterparts.

Vitamin D is associated with body composition and fat intake, but not with cardiometabolic parameters in adults with obesity

Adults with obesity are at higher risk for developing hypovitaminosis D. Some studies suggest that reduced levels of serum 25-hydroxyvitamin D (25(OH)D) may also be related to disorders in cardiometabolic parameters. However, because of the association between 25(OH)D and obesity, we hypothesized that body composition can be a confounding factor in the association of 25(OH)D with cardiometabolic parameters, and that 25(OH)D is inversely associated with body composition and cardiometabolic parameters and directly associated with fat intake. The aim of this study was to analyze the associations between 25(OH)D with body composition, fat intake, and cardiometabolic parameters in adults with obesity. This cross-sectional study consisted of 52 adults with obesity (61.53% female; 37.50 ± 6.88 years; body mass index [BMI]: 33.60 ± 2.89 kg/m²). Cardiometabolic parameters (fasting blood glucose, insulin resistance index, C-reactive protein, blood pressure, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and cholesterol), body mass, BMI, waist circumference, body fat percentage, and fat intake were evaluated. Body mass was negatively associated with 25(OH)D (β = -0.108; P = .048; and R² = 0.090) and BMI (β = -0.621; P = .031; and R² = 0.103), both adjusted for fat intake. 25(OH)D was positively associated with fat intake (β = 0.129; P = .045 and R² = 0.078) adjusted for sex, age, and skin color. Cardiometabolic parameters were not associated with 25(OH)D, even after adjusted by body composition variables. However, the high prevalence of hypovitaminosis D (75%) and the negative association between 25(OH)D and body composition reinforce the importance of analyzing and monitoring vitamin D status in this population.

The relationship between weight change history and 25(OH)D concentrations in adults

Introduction

Background: although obesity has been consistently associated with lower 25-OH hydroxyvitamin D-25(OH)D-levels, little is known about the effect of weight change on said 25(OH)D levels. Methods: the present analysis was based on data from the National Health and Nutrition Examination Survey. Percent weight changes were calculated from participant-reported maximum lifetime weight and weight in the past year and 10 years ago. Subsequently, general linear models adjusted for potential confounders were assembled to examine 25(OH)D concentrations across percent weight change categories. Results: a total of 6,237 participants with a mean age of 57.5 (SE, 0.2) years comprised the study sample. After adjustment for potential confounders, subjects who have gained weight ≥ 5 % in the past year and 10 years before had on average 4.5 and 5.1 nmol/L lower 25(OH)D levels than those with a stable weight, respectively. Moreover, this association persisted even among participants with adequate vitamin D intake. Notably, subjects who lost weight > 5 % from their maximum reported weight had significantly higher 25(OH)D levels than those who did not. Conclusion: subjects with a stable weight and those who lost weight ≥ 5% from their maximum reported lifetime weight had significantly higher 25(OH)D concentrations than those who did not. Thus, maintaining a healthy weight over time may be an effective strategy to reach optimal serum 25(OH)D levels.

Circulating Vitamin D Levels and DNA Repair Capacity in Four Molecular Subtypes of Women with Breast Cancer

Vitamin D regulates estrogen synthesis among other mechanisms involved in breast cancer (BC) development; however, no evidence has been found regarding its relationship with DNA repair capacity (DRC). Therefore, the objective of this study was to elucidate whether DRC levels are linked with plasma 25(OH)D levels. BC cases and controls were selected from our BC cohort. DRC levels were assessed in lymphocytes through the host-cell reactivation assay. 25(OH)D levels were measured using the UniCel DxI 600 Access Immunoassay System. BC cases (n = 91) showed higher 25(OH)D levels than the controls (n = 92) (p = 0.001). When stratifying BC cases and controls into low and high DRC categories, BC cases with low DRC (n = 74) had the highest 25(OH)D levels (p = 0.0001). A positive correlation between 25(OH)D and DRC levels was found for the controls (r = 0.215, p = 0.043) while a negative correlation was found for BC cases (r = −0.236, p = 0.026). Significant differences in 25(OH)D levels were observed when stratifying by molecular subtypes (p = 0.0025). Our study provides evidence of a link between 25(OH)D and DRC in BC along with a description of to how 25(OH)D levels vary across subtypes. The positive correlation observed in the control group suggests that 25(OH)D contributes differently to DRC levels once the malignancy is developed.

Prevalence and Determinants of Vitamin D Deficiency Among the Overweight and Obese Singaporeans Seeking Weight Management Including Bariatric Surgery: a Relationship with Bone Health

PURPOSE

Low vitamin D status is prevalent worldwide and has been linked to a variety of pathologies including obesity in adults. The severity of vitamin D deficiency amongst the overweight and obese Singaporeans is not well documented. The purpose of this prospective observational study was to assess the prevalence and determinants of vitamin D deficiency in a multi-ethnic Asian population referred for weight management, including those seeking bariatric surgery.

MATERIALS AND METHODS

This was a cross-sectional study conducted among 111 consecutive subjects referred to a single institution weight management service in Singapore. The data collected included their anthropometric data, body mass index (BMI), body fat percentage, waist circumference, 25-hydroxyvitamin D [25(OH)D] and other bone turnover markers.

RESULTS

The average BMI among the 111 subjects was 40.1 ± 8.2 kg/m² and mean age of 40 ± 10 years. Vitamin D deficiency was found in 75.7% of the population. There was a significant negative association of vitamin D with adiposity markers including BMI (r = - 0.31), body fat percentage (r = - 0.34) and waist circumference (r = - 0.26). Predictors of vitamin D deficiency included age > 50 years, female gender, waist circumference and body fat percentage.

CONCLUSION

Vitamin D deficiency is prevalent among this target population in Singapore regardless of ethnicity. In particular, the elderly, females, those with larger waist circumference and body fat percentage were significantly associated with lower serum 25(OH)D level. Hence, routine screening for the overweight and obese subjects in multi-ethnic Singapore seeking weight management is indicated.

The Association between Body Mass Index and Vitamin D Supplement Use among Adults in the United States

Background

Obesity has been consistently associated with lower 25-hydroxyvitamin D (25(OH)D) concentrations. BMI status also has a major impact on 25(OH)D levels among vitamin D supplement users. In our cross-sectional study, we aimed to discuss the prevalence of vitamin D supplement use and its effect on 25(OH)D levels according to BMI status among US adults.

Methods

The present analysis was based on data from the National Health and Nutrition Examination Survey (NHANES) cycles 2011-2012 through 2013-2014. The prevalence of vitamin D supplement use according to BMI status among subjects aged 20 years and older by selected characteristics was analyzed. Logistic regression models were assembled to examine the independent association of BMI status and vitamin D supplement use. Similarly, general linear models were used to assess the effect of daily vitamin D supplementation doses (<400 IU, 400-800 IU, and >800 IU) on 25(OH)D concentrations according to BMI status.

Results

Of 10,076 participants with a mean age of 47.2 [standard error (SE): 0.4] years, 57.5% (SE: 1.7) of normal-weight and 63.5% (SE: 0.9) of obese subjects reported not taking vitamin D supplements over the previous 30 days. After adjustment for potential confounders, obese subjects were 1.3 times more likely to be nonusers of vitamin D supplements and were 24% less likely to take vitamin D supplements ≥400 IU/day compared with their normal-weight counterparts. In addition, significant differences in mean 25(OH)D levels of vitamin D supplementation doses were consistently seen across BMI categories. Indeed, obese and overweight participants taking >800 IU/day of vitamin D supplements had 15.5 and 8.1 nmol/L lower mean concentrations of 25(OH)D than their normal-weight counterparts on average, respectively.

Conclusion

Obese subjects had a lower prevalence of vitamin D supplement use compared with their normal-weight counterparts. This nutritional disparity may also contribute to low 25(OH)D concentrations seen in obesity. However, a daily vitamin D supplement intake between 400 IU and 800 IU appears to be adequate among obese subjects to achieve optimal 25(OH) levels. 

Serum vitamin D and cognition in a cohort of Boston-area Puerto Ricans

Background: Vitamin D has been suggested as a protective factor for cognitive health, however results of prior studies have been mixed. To examine whether serum 25(OH)D concentration is related to cognition and cognitive decline in a study of Boston Area Puerto Ricans. Methods: We examined the association between serum 25(OH)D, cognitive function and cognitive decline in a longitudinal study of 967 Boston Area Puerto Rican adults. Results: In analyses adjusted for potential confounders, participants in the bottom quintile of 25(OH)D had similar cognitive function at baseline, as measured by a global cognitive score (mean difference: 0.09 (95% CI: -0.02, 0.19); p-trend: 0.18), and similar 2-year rates of cognitive decline (mean difference: -0.01 (95% CI: -0.09, 0.07), p-trend: 0.61) as those in the top 25(OH)D quintile. No significant associations were observed between baseline serum 25(OH)D concentration and 2-year change in individual cognitive test scores or change in executive function or memory domains. Conclusions: We observed no significant association between serum 25(OH)D and cognition in this cohort of Boston Area Puerto Ricans.

Vitamin D supplementation and body fat mass: a systematic review and meta-analysis

Studies have indicated that 25-hydroxyvitamin D (25(OH)D) level in obese is lower than normal weight subjects; however, results of studies that investigated relationship between 25(OH)D and fat mass are inconsistent. In addition, several randomized clinical trials (RCTs) have studied the influence of cholecalciferol supplement on percentage fat mass (PFM) but their results are conflicting. The objectives were to investigate the association between vitamin D3 and PFM pooling together observational studies and RCTs. PubMed/MEDLINE, Cochrane, and Scopus were comprehensively searched from inception to September 2016. The Fisher's Z (SE) of correlation coefficient and mean (SD) of changes in PFM from baseline were used to perform meta-analysis in observational studies and RCTs, respectively. To determine potential source of heterogeneity, subgroup and meta-regression analyses were conducted. Pooling correlation coefficients showed an inverse association between PFM (Fisher's Z: - 0.24, 95% CI: - 0.30 to -0 .18) and FM (Fisher's Z: - 0.32, 95% CI: - 0.43 to - 0.22) and 25(OH)D. Subgroup analysis revealed continent but not gender influence on the effect size. Meta-regression analysis indicated that age, latitude, and longitude are not sources of heterogeneity. Combining trials showed vitamin D3 supplementation had a mild but insignificant effect on PFM (- 0.31%, 95% CI: - 1.07 to 0.44). Subgroup analyses indicated that type of cholecalciferol and treatment regimens explain source of heterogeneity. Age, baseline body mass index, dose of cholecalciferol, length of study, female (%), and baseline 25(OH)D are not source of heterogeneity. In conclusion, our results state that 25(OH)D level is inversely correlated with PFM but cholecalciferol supplementation had no effect on PFM.

Body Mass Index, Vitamin D, and Type 2 Diabetes: A Systematic Review and Meta-Analysis

The deficiency of vitamin D is prevalent all over the world. Studies have shown that vitamin D may play an important role in the development of obesity. The current study was conducted to quantitatively evaluate the association between serum 25-(OH) vitamin D levels and the risk of obesity in both diabetic and non-diabetic subjects. A systematic review and meta-analysis of observational studies was carried out for that purpose. We searched the Medline, PubMed, and Embase databases throughout all of March 2018. A total of fifty five observational studies for both diabetic and non-diabetic subjects were finally included in the meta-analysis. The data were analyzed by comprehensive meta-analysis software version 3 and the random effects model was used to analyze the data. The meta-analysis showed an overall inverse relationship between serum vitamin D status and body mass index (BMI) in studies of both diabetic (r = −0.173, 95% = −0.241 to −0.103, p = 0.000) and non-diabetic (r = −0.152, 95% = −0.187 to −0.116, p = 0.000) subjects. The evidence of publication bias was not found in this meta-analysis. In conclusion, the deficiency of vitamin D is associated with an increased level of BMI in the studies of both diabetic and non-diabetic subjects. Reliable evidence from well-designed future randomized controlled trials is required to confirm the findings from observational studies and to find out the potential regulatory effects of vitamin D supplementation to lower BMI.

Fat Mass Is Associated with Serum 25-Hydroxyvitamin D Concentration Regardless of Body Size in Men

There are no large community-based studies examining the association of body size vs. body fat with vitamin D status. Association of serum 25-hydroxyvitamin D (25OHD) with body weight and subcategories of body weight defined by fat mass were evaluated in a large, free living population. Out of a total of 29,235 subjects from the 2008–2010 Korean National Health and Nutrition Examination Survey, the relevant data included 6458 subjects over 50 years of age who were analyzed cross-sectionally. Serum 25OHD concentrations were compared in men (n = 3164) and in women (n = 3294) by tertiles of body weight and body fat mass, as measured by Dual-energy X-ray Absorptiometry (DXA) within sex-specific tertiles of body weight. Serum 25OHD was weakly inversely correlated with body weight in the men and the women after adjustment for age (r = −0.075 and −0.073, respectively, p < 0.001 for both). Within each tertile of body weight, serum 25OHD decreased progressively as fat mass increased in men. This pattern was similar in the women but not consistently significant. Whereas body weight predicted a small decrease in serum 25OHD in the men and the women, greater adiposity, for any given weight, predicted larger decreases in the men, but not consistently in women.

Associations of vitamin D with insulin resistance, obesity, type 2 diabetes, and metabolic syndrome

The aim of this study is to determine the relationships of vitamin D with diabetes, insulin resistance obesity, and metabolic syndrome. Intra cellular vitamin D receptors and the 1-α hydroxylase enzyme are distributed ubiquitously in all tissues suggesting a multitude of functions of vitamin D. It plays an indirect but an important role in carbohydrate and lipid metabolism as reflected by its association with type 2 diabetes (T2D), metabolic syndrome, insulin secretion, insulin resistance, polycystic ovarian syndrome, and obesity. Peer-reviewed papers, related to the topic were extracted using key words, from PubMed, Medline, and other research databases. Correlations of vitamin D with diabetes, insulin resistance and metabolic syndrome were examined for this evidence-based review. In addition to the well-studied musculoskeletal effects, vitamin D decreases the insulin resistance, severity of T2D, prediabetes, metabolic syndrome, inflammation, and autoimmunity. Vitamin D exerts autocrine and paracrine effects such as direct intra-cellular effects via its receptors and the local production of 1,25(OH)₂D₃, especially in muscle and pancreatic β-cells. It also regulates calcium homeostasis and calcium flux through cell membranes, and activation of a cascade of key enzymes and cofactors associated with metabolic pathways. Cross-sectional, observational, and ecological studies reported inverse correlations between vitamin D status with hyperglycemia and glycemic control in patients with T2D, decrease the rate of conversion of prediabetes to diabetes, and obesity. However, no firm conclusions can be drawn from current studies, because (A) studies were underpowered; (B) few were designed for glycemic outcomes, (C) the minimum (or median) serum 25(OH) D levels achieved are not measured or reported; (D) most did not report the use of diabetes medications; (E) some trials used too little (F) others used too large, unphysiological and infrequent doses of vitamin D; and (G) relative paucity of rigorous clinical data on the effects of vitamin D sufficiency on non-calcium endpoints. Although a large number of observational studies support improving T2D, insulin resistance, obesity, and metabolic syndrome with vitamin D adequacy, there is a lack of conclusive evidence from randomized control clinical trials that, these disorders are prevented following optimization of serum levels of 25(OH)D. However, none of the currently conducted clinical studies would resolve these issues. Thus, specifically designed, new clinical studies are needed to be conducted in well-defined populations, following normalizing the serum vitamin D levels in vitamin D deficient prediabetes subjects, to test the hypothesis that hypovitaminosis D worsens these disorders and correction would alleviate it.

Vitamin D in obesity

PURPOSE OF REVIEW

Vitamin D is essential for bone health, and may also have important functions in immunity and other systems. Vitamin D deficiency is common, and testing and supplementation is increasing. Serum vitamin D is lower in obese people; it is important to understand the mechanism of this effect and whether it indicates clinically significant deficiency.

RECENT FINDINGS

Vitamin D is fat soluble, and distributed into fat, muscle, liver, and serum. All of these compartments are increased in volume in obesity, so the lower vitamin D likely reflects a volumetric dilution effect and whole body stores of vitamin D may be adequate. Despite lower serum vitamin D, obese adults do not have higher bone turnover or lower bone mineral density. Patients undergoing bariatric surgery do have bone loss, and ensuring vitamin D sufficiency in these patients may help to attenuate bone loss.

SUMMARY

Lower vitamin D in obese people is a consistent finding across age, ethnicity, and geography. This may not always reflect a clinical problem. Obese people need higher loading doses of vitamin D to achieve the same serum 25-hydroxyvitamin D as normal weight.

Correlates and family aggregation of vitamin D concentrations in school-aged children and their parents in nine Mesoamerican countries

Objective

To determine the associations of sociodemographic characteristics, diet and outdoor activity as an indicator of sun exposure with serum 25-hydroxyvitamin D (25(OH)D) concentrations in children and their parents from Mesoamerica. We also quantified family aggregation of serum 25(OH)D.

Design

Cross-sectional study. Serum 25(OH)D concentrations were quantified using immunoassay. We compared the distribution of 25(OH)D concentrations in adults and children by levels of each correlate with the use of linear regression. Family aggregation was estimated using Pearson and intraclass correlation coefficients.

Setting

Capital cities of Guatemala, El Salvador, the Dominican Republic, Honduras, Nicaragua, Costa Rica, Panama and Belize, and Tuxtla Gutiérrez in Mexico.

Subjects

Children (n223) aged 7–12 years and 492 parents.

Results

Mean (sd) 25(OH)D concentrations in adults and children were 81·3 (21·1) and 79·5 (18·1) nmol/l, respectively. Prevalence of vitamin D deficiency (VDD; 25(OH)D <50 nmol/l) was 3·9 % among adults and 3·6 % among children. In adults, adjusted mean 25(OH)D concentrations were highest in Nicaragua (P<0·0001). Serum 25(OH)D was positively related to time spent gardening (P=0·03). Among children, 25(OH)D concentrations were positively associated with male sex (P=0·005), dairy intake (P=0·03) and mother’s serum 25(OH)D concentrations (P<0·0001); and inversely associated with mother’s BMI (P=0·02) and number of home assets (P=0·04). Family membership explained 31 % of the variability in 25(OH)D concentrations; aggregation was highest between mothers and children.

Conclusions

VDD prevalence was low in this study. Sociodemographic characteristics, diet and outdoor activity predict serum 25(OH)D. Family aggregation of serum 25(OH)D is high between mothers and children.

Association between Obesity and Serum 25(OH)D Concentrations in Older Mexican Adults

Background: Vitamin D is essential for maintaining bone mineralization and calcium homeostasis, and prevents falls and fractures in older adults. Mexico is undergoing an epidemiologic and demographic transition with increasing obesity rates. The study’s aim was to determine the association of obesity with serum 25-hydroxyvitamin D [25(OH)D] concentrations in older Mexican adults. Methods: Data from 1772 Mexicans, aged ≥50 years, enrolled in a sub-sample of the 3rd wave of the Mexican Health and Aging Study, were included. Serum 25(OH)D concentrations were used to define vitamin D status, and were categorized into tertiles. Body mass index measures were used to categorize older adults into under/normal weight, overweight, and obese groups. Multinomial logistic regression models were used to assess the relationship, adjusting for potential confounders. Results: Approximately 40% and 37% of older Mexican adults were either overweight or obese, respectively. Compared to under/normal weight older Mexicans, obese adults were 1.78 times (95% Confidence Interval (CI) 1.27–2.48) and 1.94 times (95% CI 1.40–2.68) more associated with the first and second tertile concentrations of serum 25(OH)D, respectively. Overweight adults were 1.52 times (95% CI 1.12–2.06) more associated with the second tertile of serum 25(OH)D concentration than under/normal weight adults. Conclusion: Overweight/Obesity was found to be significantly associated with low concentrations of serum 25(OH) in older Mexican adults.

Free 25-hydroxyvitamin D is low in obesity, but there are no adverse associations with bone health

BACKGROUND

The mechanism and clinical significance of low circulating 25-hydroxyvitamin D [25(OH)D] in obese people are unknown. Low total 25(OH)D may be due to low vitamin D-binding proteins (DBPs) or faster metabolic clearance. However, obese people have a higher bone mineral density (BMD), which suggests that low 25(OH)D may not be associated with adverse consequences for bone.

OBJECTIVE

We sought to determine whether 1) vitamin D metabolism and 2) its association with bone health differ by body weight.

DESIGN

We conducted a cross-sectional observational study of 223 normal-weight, overweight, and obese men and women aged 25-75 y in South Yorkshire, United Kingdom, in the fall and spring. A subgroup of 106 subjects was also assessed in the winter. We used novel techniques, including an immunoassay for free 25(OH)D, a stable isotope for the 25(OH)D3 half-life, and high-resolution quantitative tomography, to make a detailed assessment of vitamin D physiology and bone health.

RESULTS

Serum total 25(OH)D was lower in obese and overweight subjects than in normal-weight subjects in the fall and spring (geometric means: 45.0 and 40.8 compared with 58.6 nmol/L, respectively; P < 0.001) but not in the winter. Serum 25(OH)D was inversely correlated with body mass index (BMI) in the fall and spring and in the winter. Free 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)2D] were lower in obese subjects. DBP, the DBP genotype, and the 25(OH)D3 half-life did not differ between BMI groups. Bone turnover was lower, and bone density was higher, in obese people.

CONCLUSIONS

Total and free 25(OH)D and 1,25(OH)2D are lower at higher BMI, which cannot be explained by lower DBP or the shorter half-life of 25(OH)D3 We speculate that low 25(OH)D in obesity is due to a greater pool of distribution. Lower 25(OH)D may not reflect at-risk skeletal health in obese people, and BMI should be considered when interpreting serum 25(OH)D as a marker of vitamin D status.

Association between serum 25-hydroxyvitamin D levels and adiposity measurements in the general Korean population

BACKGROUND/OBJECTIVES

Obesity, which is a known risk factor for many chronic diseases, has also been associated with vitamin D deficiency. This study explored the relationship between serum 25-hydroxy-vitamin D [25(OH)D] concentrations and adiposity measures in a general Korean population using the most recent, nationally representative survey data.

SUBJECTS/METHODS

The study sample consisted of 4,771 Korean adults (≥ 19 years) who participated in the fifth Korean National Health and Nutrition Examination Surveys. Serum 25(OH)D was determined by radioimmunoassay. Body mass index (BMI), waist circumference (WC) and total body fat content were measured as adiposity measurements. Total body fat content was measured by dual-energy X-ray absorptiometry.

RESULTS

The serum 25(OH)D level was significantly higher in men than in women. Serum 25(OH)D concentration was positively correlated with energy intake, and it was negatively correlated with total body fat content (P < 0.0001) and percentage body fat (P < 0.0001) after adjustment for age in both sexes, while was inversely correlated with BMI only in women. In multivariable regression analysis, serum 25(OH)D was inversely associated with the total body fat content after adjustment for age, BMI, education, region, smoking, alcohol consumption, physical activity, and energy intake only in men (P = 0.0047). However, the serum 25(OH)D concentration was not associated with WC or BMI, indicators of adiposity after adjustment for potential risk factors.

CONCLUSIONS

Serum 25(OH)D concentration was independently associated with the total body fat content in a general Korean population, but it may be not associated with the indicators for estimating adiposity, such as WC or BMI.

Prevalence of hypovitaminosis D and its association with comorbidities of childhood obesity

PURPOSE

Our study sought to further delineate the prevalence of hypovitaminosis D and its relationship to comorbidities of childhood obesity.

METHODS

We conducted a retrospective chart review from 155 obese children aged 5 to 19 years who attended the Penn State Children’s Hospital Pediatric Multidisciplinary Weight Loss Program from November 2009 through November 2010. We determined the incidence of hypovitaminosis D and examined its association with comorbidities including elevated blood pressure, diabetes, acanthosis nigricans, depression, hyperlipidemia, hyperinsulinemia, and abnormal liver function test results, as well as age, sex, and geographic location.

RESULTS

Under the latest Institute of Medicine definitions, vitamin D deficiency (< 20 ng/mL) and insufficiency (20-29 ng/mL) was present in 40% and 38% of children, respectively. The prevalence of vitamin D deficiency was 27.8% in children aged 5 to 9 years, 35.4% in children aged 10 to 14 years, and 50.9% of children aged 15 years or older. Older age, African-American race, winter/spring season, higher insulin level, total number of comorbidities, and polycystic ovary syndrome (in girls) were significantly associated with vitamin D deficiency. African-American race, winter/spring season, hyperinsulinemia, elevated systolic blood pressure, urban location, and total numbers of comorbidities were significantly associated with hypovitaminosis D (< 30 ng/mL).

CONCLUSIONS

Hypovitaminosis D is associated with several medical comorbidities in obese children. Given the large percentage of children, even in our youngest age group, who are vitamin D deficient, obese children should be considered for routine vitamin D screening.

Prevalence of Vitamin D Insufficiency and Deficiency among Young Physicians at University District Hospital in San Juan, Puerto Rico

Vitamin D has been attracting increased attention because of higher prevalences of vitamin D insufficiency and deficiency than expected in areas with sufficient sun exposure. Even though sunlight exposure and diet are the main determinants of vitamin D status, other factors, such as age, race, the use (or not) of sunscreen, medications, and malabsorptive conditions, also affect vitamin D levels. Recent studies have found high prevalences of vitamin D deficiency and insufficiency in different populations. However, there are limited data regarding the prevalence of vitamin D deficiency and insufficiency in Puerto Rico. To shed more light on the subject, we evaluated a sample of 51 internal medicine residents and research fellows, aged from 25 to 39 years at the University District Hospital in San Juan, Puerto Rico, doing so by means of a questionnaire that explored basic socio demographic and lifestyle characteristics and collected anthropometric data; in addition, we obtained blood samples in order to determine 25-hydroxyvitamin D levels. The median 25-hydroxyvitamin D level was 21 ng/mL (range, 7-38 ng/mL). Forty-five participants (88.2%) had 25-hydroxyvitamin D concentrations of lower than 30 ng/mL. We found vitamin D deficiencies in 43.1% of the population and insufficiencies in 45.1%. Contributory factors to our findings include limited exposure to sunlight during periods of high sun intensity, increased body mass index, and a limited area of the body being exposed to sunlight. A relationship between reduced physical activity levels and hypovitaminosis D was also found. Both calcium intake and vitamin D intake, which were markedly below recommended daily allowances, were positively correlated with 25-hydroxy vitamin D levels, but with a weak association.

Vitamin D status is inversely associated with obesity in a clinic-based sample in Puerto Rico

Studies show that vitamin D status is associated to obesity but data in Hispanic individuals is scarce. The aim of this study was to assess the association between vitamin D status and obesity in a clinic-based sample in Puerto Rico. We hypothesized that subjects with a higher adiposity would have a lower vitamin D status. We extracted the following data from medical records of a private clinic: age, gender, serum 25(OH)D levels, weight, height, and waist circumference. Body mass index (BMI) (kg/m(2)) and waist-to-height ratio were calculated and categorized according to standard guidelines. Statistical analyses included analysis of covariance, Pearson correlations and χ(2) test. From 797 individuals (mean age 53.7 ± 15.4 years; 63.5% females), 35.6% were overweight and 43.7% obese. Mean 25(OH)D levels were 24.7 ± 8.7 ng/mL; 5.3% had levels <12 ng/mL, 30.6% had levels 12 to 20 ng/mL, and 43.5% had levels 21 to 30 ng/mL. Mean 25(OH)D levels were significantly higher in normal weight and overweight males compared to obese males (P < .05) and in overweight females compared to obese females (P < .05). Levels were also higher in those with low risk compared to high risk of waist circumference and waist-to-height ratio (P < .001). BMI, waist circumference, and waist-to-height ratio were inversely correlated to 25(OH)D levels (P < .001). A greater proportion of obese individuals (41.4%) were vitamin D deficient or insufficient compared to the normal weight (33.9%) and overweight individuals (30.3%) (P < .05). In conclusion, in this clinic-based sample of Puerto Rican adults, those with higher BMI, waist circumference, and waist-to-height ratio had a significantly lower vitamin D status.

Importance of vitamin D and vitamin D levels status in Puerto Ricans

There is growing and compelling evidence demonstrating the extra-skeletal role of vitamin D and the importance of maintaining adequate levels of this nutrient. Currently, there is very limited information available on the vitamin D status in children and adults in underserved groups, including Puerto Ricans. We assessed the vitamin D status of 4,090 Puerto Ricans living in six geographical regions in the island. Only 31.5% of the studied population had sufficient vitamin D levels (>30 ng/ml). The 18-39 year age group and the females showed inadequate (&lt;30 ng/ml) levels of vitamin D (76.9% and 69.8%, respectively). Participants aged 60 or older showed the highest mean values of serum 25(OH)D (28.8 ng/ml) and the highest percentage (37.1%) of sufficient levels (>30 ng/ml). Future studies are certainly warranted to understand the prevalence of vitamin D deficiency and influencing factors (including obesity) in Puerto Ricans.

Serum vitamin D is low and inversely associated with LDL cholesterol in the Kazak ethnic population: a cross-sectional study

Background

Accumulating evidence suggests that low concentrations of serum 25(OH)D is coupled with increased risks of hypertension, obesity, and cardiovascular disease. However, this relationship has not been established in populations with very low levels of 25(OH)D. Therefore, the aim of our study was to clarify the associations between 25(OH)D and blood pressure, obesity, sex, and lipid profiles in the Kazak ethnic population, who have an extremely low level of 25(OH)D.

Material/Methods

A multistage-cluster sampling survey was carried out for residents with Kazak ethnicity in Xinjiang, China. Anthropometric measurements of each participant were taken and the concentrations of 25(OH)D, calcium, alkaline phosphatase, and lipid profiles were measured. Individuals were classified into different groups in terms of vitamin D status, degree of adiposity, presence of hypertension, and other comorbidities.

Results

The madian concentration of 25(OH)D was 16.2 (11.8–20.5) ng/mL and the prevalence of vitamin D deficiency was 72.4% in this Kazak population (n=928, 59.0% women). Females had a lower 25(OH)D concentration than males – 14.6 (10.5–19.4) ng/mL vs. 17.7 (14.8–22.5) ng/mL, P<0.001. The subjects were classified into 3 groups according to their vitamin D status. There were significant differences in BMI (P=0.046), waist circumference (P=0.037), hip circumference (P=0.003), systolic BP (P=0.035), and LDL cholesterol (P=0.008) among the groups after adjustment for sex and age. On the other hand, there was no significant difference in vitamin D levels between groups with or without hypertension (P=0.586), and groups with or without obesity (P=0.639). A multifactor-regression analysis revealed that every increment of 1mg/dL in LDL cholesterol was associated with a 1.0 ng/mL decline in serum 25(OH)D.

Conclusions

The insufficiency of vitamin D is highly prevalent in Kazaks. Sex, LDL cholesterol, and hip circumference are 3 variables strongly associated with serum 25(OH)D concentration. In a population with low levels of 25(OH)D, the negative relationship between obesity and serum 25(OH)D, a common finding from most previous studies, could not be established.

Association between vitamin D levels and blood pressure in a group of Puerto Ricans

OBJECTIVE

Hypertension is a global public health problem. The apparent association between vitamin D (VitD) and blood pressure (BP) has been studied in several populations but not in a Puerto Rican population. Therefore, we determined the association between serum 25(OH)D levels and BP in a convenience sample in Puerto Rico.

METHODS

A cross-sectional study of patients attending a local laboratory with an order for serum 25(OH)D levels was performed. Participants completed a questionnaire that solicited the following information: age, sex, weight, height, VitD intake, and history of both sun exposure and hypertension. BP was measured by a phlebotomist on-site and classified according to the Joint National Committee; serum 25(OH)D levels were taken from the record, and VitD status was classified as either optimal (25(OH)D > or = 30 ng/dl) or non-optimal (< 30 ng/dl). Mean, standard deviation, and percentiles were used for descriptive analysis. VitD status and BP were compared by gender, age, and body mass index (BMI) using ANOVA or chi-square. The association between VitD status and blood pressure was assessed by polytomous logistic regression adjusting for several variables.

RESULTS

Two hundred nineteen individuals were included in the analysis; most were females aged 21 to 50 years who were overweight/obese; 53% of the total population was pre-hypertensive or hypertensive; 60% had non-optimal VitD status; and the sun exposure index was 19.6. No significant associations were found between VitD status and blood pressure after adjusting for age, sex, BMI, total VitD intake, and solar exposure index.

CONCLUSION

VitD status was not found to be associated with blood pressure in this sample population; more studies with a larger sample population are needed to determine whether such an association does in fact exist.

Vitamin D insufficiency and severe asthma exacerbations in Puerto Rican children

RATIONALE

Vitamin D insufficiency (a serum 25(OH)D <30 ng/ml) has been associated with severe asthma exacerbations, but this could be explained by underlying racial ancestry or disease severity. Little is known about vitamin D and asthma in Puerto Ricans.

OBJECTIVES

To examine whether vitamin D insufficiency is associated with severe asthma exacerbations in Puerto Rican children, independently of racial ancestry, atopy, and time outdoors.

METHODS

A cross-sectional study was conducted of 560 children ages 6-14 years with (n = 287) and without (n = 273) asthma in San Juan, Puerto Rico. We measured plasma vitamin D and estimated the percentage of African racial ancestry among participants using genome-wide genotypic data. We tested whether vitamin D insufficiency is associated with severe asthma exacerbations, lung function, or atopy (greater than or equal to one positive IgE to allergens) using logistic or linear regression. Multivariate models were adjusted for African ancestry, time outdoors, atopy, and other covariates.

MEASUREMENTS AND MAIN RESULTS

Vitamin D insufficiency was common in children with (44%) and without (47%) asthma. In multivariate analyses, vitamin D insufficiency was associated with higher odds of greater than or equal to one severe asthma exacerbation in the prior year (odds ratio [OR], 2.6; 95% confidence interval [CI], 1.5-4.9; P = 0.001) and atopy, and a lower FEV(1)/FVC in cases. After stratification by atopy, the magnitude of the association between vitamin D insufficiency and severe exacerbations was greater in nonatopic (OR, 6.2; 95% CI, 2-21.6; P = 0.002) than in atopic (OR, 2; 95% CI, 1-4.1; P = 0.04) cases.

CONCLUSIONS

Vitamin D insufficiency is associated with severe asthma exacerbations in Puerto Rican children, independently of racial ancestry, atopy, or markers of disease severity or control.