Perfil de vitamina D e sua associação com adiposidade corporal e resistência à insulina em pacientes com doença renal crônica na fase não dialítica

O termo vitamina D compreende um grupo de hormônios esteróides com ações biológicas semelhantes. O método mais acurado para determinar o estado de vitamina D é através dos níveis plasmáticos de 25 hidroxivitamina D [25(OH)D]. A deficiência de 25(OH)D é considerada um problema de saúde pública, tendo como principal causa à baixa exposição solar, idade avançada e doenças crônicas. A deficiência de 25(OH)D é frequente em pacientes com doença renal crônica (DRC) na fase não dialítica. Estudos têm evidenciado que os níveis séricos de 25(OH)D apresentam associação inversa com adiposidade corporal e resistência à insulina (RI) na população em geral e na DRC. O excesso de gordura corporal e o risco de Doença Cardiovascular (DVC) vêm sendo estudados em pacientes com DRC e dentre as complicações metabólicas associadas à adiposidade corporal elevada observa-se valores aumentados de HOMA-IR (Homeostasis Model Assessment of Insulin Resistance) um marcador para RI. Estudos avaliando o perfil da 25(OH)D na DRC na fase não dialítica, especialmente relacionados com a adiposidade corporal e RI são escassos. O presente estudo tem como objetivo avaliar a relação entre os níveis séricos de 25(OH)D, RI, e adiposidade corporal em pacientes com DRC na fase não dialítica. Trata-se de um estudo transversal observacional, incluindo pacientes adultos, clinicamente estáveis e com filtração glomerular estimada (FGe) ≤ 60 ml/min., em acompanhamento regular no Núcleo Interdisciplinar de Tratamento da DRC. Os participantes foram submetidos à avaliação do estado nutricional por antropometria (peso, altura, índice de massa corporal (IMC), circunferências e dobras cutâneas) e absorciometria de duplo feixe de raios X (DXA); foram avaliados no sangue: creatinina, uréia, glicose, albumina, colesterol total e frações e triglicérides, além de leptina, insulina e 25(OH)D. Níveis séricos < 20ng/dL de 25(OH)D foram considerados como deficiência. As análises estatísticas foram realizadas utilizando-se o software STATA versão 10.0, StataCorp, College Satation, TX, USA. Foram avaliados 244 pacientes (homens n=135; 55,3%) com média de idade de 66,3 13,4 anos e de FGe= 29,4 12,7 ml/min. O IMC médio foi de 26,1 kg/m (23,0-30,1) com elevada prevalência de sobrepeso/obesidade (58%). A adiposidade corporal total foi elevada em homens (gordura total-DXA= 30,2 7,6%) e mulheres (gordura total-DXA= 39,9 6,6%). O valor mediano de 25(OH) D foi de 28,55 ng/dL (35,30-50,70) e de HOMA-IR foi 1,6 (1,0-2,7). Os pacientes com deficiência de 25(OH)D (n= 51; 20,5%) apresentaram maior adiposidade corporal total (DXA% e BAI %) e central (DXA%) e valores mais elevados de leptina. A 25(OH)D apresentou correlação significante com adiposidade corporal total e central e com a leptina, mas não se associou com valores de HOMA-IR. Estes resultados permitem concluir que nos pacientes DRC fase não dialítica a deficiência de 25(OH)D e a elevada adiposidade corporal são frequentes. Estas duas condições estão fortemente associadas independente da RI; a alta adiposidade corporal total e central estão positivamente relacionadas com RI; 25(OH)H e RI não estão associados nessa população com sobrepeso/obesidade.

A importância clínica da vitamina D

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências Farmacêuticas

Vitamin D status and requirements during pregnancy and lactation

Vitamin D deficiency during pregnancy, lactation, and early infancy has been widely reported. Current understanding of vitamin D metabolism during pregnancy and lactation is incomplete, and to date, experimental data to support vitamin D requirements for these life stages are scarce. There is a shortage of nationally representative data and appropriate reference ranges for serum 25-hydroxyvitamin D (25OHD) during pregnancy, lactation and infancy, including in umbilical cord blood. This thesis described concentrations of total 25OHD and individual metabolites including 25OHD3, 25OHD2, and 3-epi-25OHD3 at 15 weeks’ gestation in a large seasonally balanced pregnancy cohort study (n 1768), carried out in Cork, Ireland (52oN). The prevalence of low 25OHD concentrations in pregnant women was higher than published reports in other Caucasian women, and was highest among non-users of vitamin D-containing supplements during winter. A longitudinal pregnancy study was included which suggested gestational stages had an impact on the total serum 25OHD concentration. This thesis incorporated a randomized controlled trial carried out among 100 women across 3 intervention groups using 20 μg/day of vitamin D3 with or without 500 mg calcium, or placebo, over 12-weeks of lactation to investigate the vitamin D requirement for lactating mothers and the vitamin D content of human milk. A daily intake of 25 μg/day was suggested to meet the requirement of lactating women to maintain a 25OHD levels above 50 nmol/L in 97.5% of the population at 52oN all year around. However, vitamin D content in human milk did not increase in response to supplementation. Serum 25OHD concentration has been used as a predictor of a number of health outcomes. This thesis reported large differences in serum 25OHD concentrations using different methods in 86 umbilical cord samples. The need for international standardization of serum 25OHD measurements was re-emphasized in this thesis.

Low vitamin D status adversely affects bone health parameters in adolescents

Background: The effects of subclinical vitamin D deficiency on bone mineral density (BMD) and bone turnover in adolescents, especially in boys, are unclear.

Objective: We aimed to investigate the relations of different stages of vitamin D status and BMD and bone turnover in a representative sample of adolescent boys and girls.

Design: BMD was measured by dual-energy X-ray absorptiometry at the nondominant forearm and dominant heel in a random sample of 12- (n = 260) and 15-y-old (n = 239) boys and 12- (n = 266) and 15-y-old (n = 250) girls. Serum 25-hydroxyvitamin D, parathyroid hormone, osteocalcin, and type I collagen cross-linked C-telopeptide were assessed by using enzyme-linked immunoassays. Relations between vitamin D status and bone health indexes were assessed by using regression modeling.

Results: Using multivariate regression to adjust for potential physical, lifestyle, and dietary confounding factors, we observed that 12-and 15-y-old girls with high vitamin D status (>= 74.1 nmol/L) had significantly greater forearm (but not heel) BMD (beta = 0.018; SE = 0.008; P < 0.05 for each age group) and lower serum parathyroid hormone concentrations and bone turnover markers than did those with low vitamin D status. These associations were evident in subjects sampled throughout the year and in winter only. There was no significant relation between vitamin D status and BMD in boys.

Conclusions: Maintaining serum 25-hydroxyvitamin D concentrations above approximate to 50 nmol/L throughout the year may be a cost-effective means of improving bone health. Increased emphasis on exploring strategies for improving vitamin D status in adolescents is needed.

Maternal Vitamin D Status in Type 1 Diabetic Pregnancy: Impact on Neonatal Vitamin D Status and Association with Maternal Glycaemic Control

Objective: The first aim of this study was to assess 25-hydroxy vitamin D (25OHD) concentrations in women with type 1 diabetes (T1DM) during pregnancy, post-delivery and also foetal (cord blood) 25OHD concentrations and to examine relationships between these. The second aim of the study was to investigate potential interactions between maternal body mass index (BMI) and foetal vitamin D status. A further study aim was to examine potential relationships between maternal 25OHD and glycosylated haemoglobin (HbA_1c) throughout pregnancy.

Research Design and Methods: This was an observational study of 52 pregnant controls without diabetes and 65 pregnant women with T1DM in a university teaching hospital. Maternal serum 25OHD was measured serially throughout the pregnancy and post-delivery. Cord blood 25OHD was measured at delivery. 25OHD was measured by liquid chromatography tandem mass spectrometry (LC-MS/MS).

Results: Vitamin D deficiency (25OHD <25 nmol/L) was apparent in both the T1DM subjects and controls at all 3 pregnancy trimesters. Vitamin D levels in all cord blood were <50 nmol/L. Maternal 25OHD correlated positively with cord 25OHD at all 3 trimesters in the T1DM group (p= 0.02; p<0.001; p<0.001). 25OHD levels within cord blood were significantly lower for women with diabetes classified as obese vs. normal weight at booking [normal weight BMI <25 kg/m² vs. obese BMI >30 kg/m² (nmol/L±SD); 19.93±11.15 vs. 13.73±4.74, p= 0.026]. In the T1DM group, HbA_1c at booking was significantly negatively correlated with maternal 25OHD at all 3 trimesters (p= 0.004; p = 0.001; p= 0.05).

Conclusion: In T1DM pregnancy, low vitamin D levels persist throughout gestation and post-delivery. Cord blood vitamin D levels correlate with those of the mother, and are significantly lower in obese women than in their normal weight counterparts. Maternal vitamin D levels exhibit a significant negative relationship with HbA_1c levels, supporting a potential role for this vitamin in maintaining glycaemic control. 

A narrow-band ultraviolet B course improves vitamin D balance and alters cutaneous CYP27A1 and CYP27B1 mRNA expression levels in haemodialysis patients supplemented with oral vitamin D

Background: Chronic kidney disease (CKD) patients on dialysis are prone to vitamin D insufficiency despite oral vitamin D supplementation. Here, we studied whether narrow-band ultraviolet B (NB-UVB) exposures improve vitamin D balance.

Methods: 14 haemodialysis patients and 15 healthy subjects receiving oral cholecalciferol 20 µg daily got nine NB-UVB exposures on the entire body. Serum 25-hydroxyvitamin D (25(OH)D) was measured by radioimmunoassay. Cutaneous mRNA expression levels of CYP27A1 and CYP27B1, two enzymes required for hydroxylation of vitamin D into its active metabolite, were also measured.

Results: The baseline serum 25(OH)D concentration was 57.6 ± 18.2 nmol/l in the CKD patients and 74.3 ± 14.8 nmol/l in the healthy subjects. The NB-UVB course increased serum 25(OH)D by 14.0 nmol/l (95% CI 8.7-19.5) and 17.0 nmol/l (CI 13.7-20.2), respectively. At baseline the CKD patients showed significantly increased CYP27B1 levels compared to the healthy subjects.

Conclusions: A short NB-UVB course is an efficient way to improve vitamin D balance in CKD patients on dialysis who are receiving oral vitamin D supplementation. The increased cutaneous CYP27B1 levels in the CKD patients suggest that the loss of renal activity of this enzyme is at least partially compensated for by the skin.

Narrow-band ultraviolet B treatment boosts serum 25-hydroxyvitamin D in patients with psoriasis on oral vitamin D supplementation

A course of treatment with narrow-band ultraviolet B (NB-UVB) improves psoriasis and increases serum 25-hydroxyvitamin D (25(OH)D). In this study 12 patients with psoriasis who were supplemented with oral cholecalciferol, 20 µg daily, were given a course of NB-UVB and their response measured. At baseline, serum 25(OH)D was 74.14 ± 22.9 nmol/l. At the 9th exposure to NB-UVB 25(OH)D had increased by 13.2 nmol/l (95% confidence interval (95% CI) 7.2–18.4) and at the 18th exposure by 49.4 nmol/l (95% CI 35.9–64.6) above baseline. Psoriasis Area Severity Index score improved from 8.7 ± 3.5 to 4.5 ± 2.0 (p < 0.001). At baseline, psoriasis lesions showed low vitamin D metabolizing enzyme (CYP27A1, CYP27B1) and high human β-defensin-2 mRNA expression levels compared with those of the healthy subjects. In conclusion, NB-UVB treatment significantly increases serum 25(OH)D in patients with psoriasis who are taking oral vitamin D supplementation, and the concentrations remain far from the toxicity level. Healing psoriasis lesions show similar mRNA expression of vitamin D metabolizing enzymes, but higher antimicrobial peptide levels than NB-UVB-treated skin in healthy subjects.

Narrow-band ultraviolet B exposure increases serum vitamin D levels in haemodialysis patients

Chronic kidney disease (CKD) patients are especially prone to vitamin D insufficiency. Narrow-band ultraviolet B (NB-UVB) treatment increases serum 25-hydroxyvitamin D [25(OH)D] in dermatological patients, and we studied whether it also improves vitamin D balance in CKD patients on haemodialysis.

High prevalence of hypovitaminosis D in a Swiss rheumatology outpatient population.

Vitamin D is important for bone metabolism and neuromuscular function. While a routine dosage is often proposed in osteoporotic patients, it is not so evident in rheumatology outpatients where it has been shown that the prevalence of hypovitaminosis D is high. The aim of the current study was to systematically evaluate the vitamin D status in our outpatient rheumatology population to define the severity of the problem according to rheumatologic diseases. During November 2009, all patients were offered a screening test for 25-OH vitamin D levels and categorised as deficient (<10 µg/l [ng/ml] [25 nmol/l]), insufficient (10 µg/l to 30 µg/l [25 to 75 nmol/l]) or normal (>30 µg/l [75 nmol/l]). A total of 272 patients were included. The mean 25-OH vitamin D level was 21 µg/l (range 1.5 to 45.9). A total of 20 patients had vitamin D deficiency, 215 patients had an insufficiency and 37 patients had normal results. In the group of patients with osteoporosis mean level of 25-OH vitamin D was 25 µg/l and 31% had normal results. In patients with inflammatory rheumatic diseases (N = 219), the mean level of 25-OH vitamin D was 20.5 µg/l, and only 12% had normal 25-OH vitamin D levels. In the small group of patients with degenerative disease (N = 33), the mean level of 25-OH vitamin D was 21.8 µg/l, and 21% had normal results. Insufficiency and deficiency were even seen in 38% of the patients who were taking supplements. These results confirm that hypovitaminosis D is highly prevalent in an outpatient population of rheumatology patients, affecting 86% of subjects. Despite oral supplementation (taken in 38% of our population), only a quarter of those on oral supplementation attained normal values of 25-OH vitamin D.

Serum 25-hydroxyvitamin D level and kidney function decline in a Swiss general adult population.

Molecular evidence suggests that levels of vitamin D are associated with kidney function loss. Still, population-based studies are limited and few have considered the potential confounding effect of baseline kidney function. This study evaluated the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline, and incidence of CKD and albuminuria. Baseline (2003-2006) and 5.5-year follow-up data from a Swiss adult general population were used to evaluate the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline (annual loss >3 ml/min per 1.73 m(2)), and incidence of CKD and albuminuria. Serum 25-hydroxyvitamin D was measured at baseline using liquid chromatography-tandem mass spectrometry. eGFR and albuminuria were collected at baseline and follow-up. Multivariate linear and logistic regression models were used considering potential confounding factors. Among the 4280 people included in the analysis, the mean±SD annual eGFR change was -0.57±1.78 ml/min per 1.73 m(2), and 287 (6.7%) participants presented rapid eGFR decline. Before adjustment for baseline eGFR, baseline 25-hydroxyvitamin D level was associated with both mean annual eGFR change and risk of rapid eGFR decline, independently of baseline albuminuria. Once adjusted for baseline eGFR, associations were no longer significant. For every 10 ng/ml higher baseline 25-hydroxyvitamin D, the adjusted mean annual eGFR change was -0.005 ml/min per 1.73 m(2) (95% confidence interval, -0.063 to 0.053; P=0.87) and the risk of rapid eGFR decline was null (odds ratio, 0.93; 95% confidence interval, 0.79 to 1.08; P=0.33). Baseline 25-hydroxyvitamin D level was not associated with incidence of CKD or albuminuria. The association of 25-hydroxyvitamin D with eGFR decline is confounded by baseline eGFR. Sufficient 25-hydroxyvitamin D levels do not seem to protect from eGFR decline independently from baseline eGFR.

Vitamin D status and latent tuberculosis infection : a preliminary study in a group of healthy Mexican agricultural workers

Vitamin D metabolites are important in the regulation of bone and calcium homeostasis, but also have a more ubiquitous role in the regulation of cell differentiation and immune function. Severely low circulating 25-dihydroxyvitamin D [25(OH)D] concentrations have been associated with the onset of active tuberculosis (TB) in immigrant populations, although the association with latent TB infection (LTBI) has not received much attention. A previous study identified the prevalence of LTBI among a sample of Mexican migrant workers enrolled in Canada's Seasonal Agricultural Workers Program (SA WP) in the Niagara Region of Ontario. The aim of the present study was to determine the vitamin D status of the same sample, and identify if a relationship existed with LTBI. Studies of vitamin D deficiency and active TB are most commonly carried out among immigrant populations to non-endemic regions, in which reactivation of LTBI has occurred. Currently, there is limited knowledge of the association between vitamin D deficiency and LTBI. Entry into Canada ensured that these individuals did not have active TB, and L TBI status was established previously by an interferon-gamma release assay (IGRA) (QuantiFERON-TB Gold In-Tube®, Cellestis Ltd., Australia). Awareness of vitamin D status may enable individuals at risk of deficiency to improve their nutritional health, and those with LTBI to be aware of this risk factor for disease. Prevalence of vitamin D insufficiency among the Mexican migrant workers was determined from serum samples collected in the summer of 2007 as part of the cross sectional LTBI study. Samples were measured for concentrations of the main circulating vitamin D metabolite, 25(OH)D, with a widely used 1251 250HD RIA (DiaSorin Inc.®, Stillwater, MN), and were categorized as deficient «37.5 nmoI/L), insufficient (>37.5 nmollL, < 80 nmol/L) or sufficient (2::80 nmoI/L). Fisher's exact tests and t tests were used to determine if vitamin D status (sufficiency or insufficiency) or 25(OH)D concentrations significantly differed by sex or age categories. Predictors of vitamin D insufficiency and 25(OH)D concentrations were taken from questionnaires carried out during the previous study, and analyzed in the present study using multiple regression prediction models. Fisher's exact test and t test was used to determine if vitamin D status or 25(OH)D concentration differed by LTBI status. Strength of the relationship between interferongamma (IFN-y) concentration (released by peripheral T cells in response to TB antigens) and 25(OH)D concentration was analyzed using a Spearman correlation. Out of 87 participants included in the study (78% male; mean age 38 years), 14 were identified as LTBI positive but none had any signs or symptoms of TB reactivation. Only 30% of the participants were vitamin D sufficient, whereas 68% were insufficient and 2% were deficient. Significant independent predictors of lower 25(OH)D concentrations were sex, number of years enrolled in the SA WP and length of stay in Canada. No significant differences were found between 25(OH)D concentrations and LTBI status. There was a significant moderate correlation between IFN-y and 25(OH)D concentrations ofLTBI-positive individuals. The majority of participants presented with Vitamin D insufficiency but none were severely deficient, indicating that 25(OH)D concentrations do not decrease dramatically in populations who temporarily reside in Canada but go back to their countries of origin during the Canadian winter. This study did not find a statistical relationship between low levels of vitamin D and LTBI which suggests that in the presence of overall good health, lower than ideal levels of 2S(OH)D, may still be exerting a protective immunological effect against LTBI reactivation. The challenge remains to determine a critical 2S(OH)D concentration at which reactivation is more likely to occur.

Homéostasie phosphocalcique et vitamine D : effets sur le cartilage de croissance par la mesure des paramètres physiques, biochimiques et géniques liés à la croissance osseuse

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Prevalencia y factores asociados a hipovitaminosis d en mujeres que acuden a un instituto endocrinológico en Bogotá

Introducción: la vitamina D es una hormona encargada de la homeostasis del calcio, su carencia está implicada en patologías del sistema óseo e inmune, se obtiene de la síntesis cutánea tras la exposición solar e ingesta de algunos alimentos. Objetivo: determinar la prevalencia y los factores asociados a Hipovitaminosis D en mujeres que acuden a un Instituto endocrinológico en la Ciudad de Bogotá. Diseño: Se estudiaron 156 mujeres adultas con patologías endocrino-metabólicas residentes en Bogotá, (~latitud 4°N), atendidas en la misma institución y con las mismas técnicas de laboratorio y de imagen, La información fue recogida de las historias clínicas electrónicas, y analizada con el programa estadístico SPSS v17. Resultados: la prevalencia de hipovitaminosis D (<30ng/mL) fue de 76.9% La mediana de vitamina D fue 22.68 ng/ml ±11.05, y de PTH fue 48.89 pg/ml ±23.64. Entre las pacientes con hipovitaminosis, el 51.7% cursó con osteopenia y el 60% con Hipotiroidismo. Del grupo sin carencia de vitamina D, el 47.2% registraron sobrepeso y el 41.7% presentó osteopenia. Se encontró relación significativa con menopausia con una p: 0.0048. No se encontró relación con PTH ni niveles de densidad mineral ósea. Conclusión: la población se seleccionó por disponibilidad de mediciones de vitamina D, sin embargo sus características pudieron influir en los resultados, existe un porcentaje importante de mujeres afectadas por la hipovitaminosis D, en quienes no se observo relación con los factores encontrados en otros estudios, se requeriría una exploración en la que se consideren factores como dieta y exposición solar.

Niveles de vitamina d y prevalencia de déficit de vitamina d en mujeres postmenopáusicas mayores de 50 años en Bogotá

Objetivo: Describir los niveles de vitamina D y calcular prevalencia de déficit de vitamina D en mujeres postmenopáusicas mayores de 50 años que asisten a consulta de medicina general en una muestra en de la ciudad de Bogotá durante el periodo 2013-2014. Pacientes y métodos: Realizamos un estudio descriptivo para estimar el déficit de VD en mujeres postmenopáusicas entre 50 y 80 años en la ciudad de Bogotá y la prevalencia de hipovitaminosis D. Durante el periodo octubre 2013 a octubre 2014 se analizaron 320 muestras, se identificaron las características socio-demográficas, patológicas y la exposición a radiación ultravioleta de cada participante. Se realizó un análisis descriptivo de las variables, se estableció su asociación con el déficit de vitamina D su aporte estadístico con al mismo. Resultados :El promedio de edad en la muestra fue de 61 años y el promedio de edad en la que reportaron la ultima menstruación fue a los 43 años. Con respecto a las características socio-demográficas 50% de las mujeres pertenecieron a los estratos 3 y 4, únicamente 11% de los pacientes realizaron una carrera universitaria y 73% de la mujeres fueron amas de casa. Con respecto a los niveles de vitamina D, 81% de los pacientes presentaron niveles anormales y el promedio de 25(OH)D en la población estudio fue de 19,81ng/ml. Conclusión: La prevalencia de déficit de vitamina D en mujeres bogotanas postmenopáusicas es significativo. Se requiere incrementar la exposición solar o dar suplencia con vitamina D para disminuir el riesgo de fracturas.

Causal relationship between obesity and vitamin D status: bi-directional mendelian randomization analysis of multiple cohorts

BACKGROUND: Obesity is associated with vitamin D deficiency, and both are areas of active public health concern. We explored the causality and direction of the relationship between body mass index (BMI) and 25-hydroxyvitamin D [25(OH)D] using genetic markers as instrumental variables (IVs) in bi-directional Mendelian randomization (MR) analysis. METHODS AND FINDINGS: We used information from 21 adult cohorts (up to 42,024 participants) with 12 BMI-related SNPs (combined in an allelic score) to produce an instrument for BMI and four SNPs associated with 25(OH)D (combined in two allelic scores, separately for genes encoding its synthesis or metabolism) as an instrument for vitamin D. Regression estimates for the IVs (allele scores) were generated within-study and pooled by meta-analysis to generate summary effects. Associations between vitamin D scores and BMI were confirmed in the Genetic Investigation of Anthropometric Traits (GIANT) consortium (n = 123,864). Each 1 kg/m(2) higher BMI was associated with 1.15% lower 25(OH)D (p = 6.52×10⁻²⁷). The BMI allele score was associated both with BMI (p = 6.30×10⁻⁶²) and 25(OH)D (-0.06% [95% CI -0.10 to -0.02], p = 0.004) in the cohorts that underwent meta-analysis. The two vitamin D allele scores were strongly associated with 25(OH)D (p≤8.07×10⁻⁵⁷ for both scores) but not with BMI (synthesis score, p = 0.88; metabolism score, p = 0.08) in the meta-analysis. A 10% higher genetically instrumented BMI was associated with 4.2% lower 25(OH)D concentrations (IV ratio: -4.2 [95% CI -7.1 to -1.3], p = 0.005). No association was seen for genetically instrumented 25(OH)D with BMI, a finding that was confirmed using data from the GIANT consortium (p≥0.57 for both vitamin D scores). CONCLUSIONS: On the basis of a bi-directional genetic approach that limits confounding, our study suggests that a higher BMI leads to lower 25(OH)D, while any effects of lower 25(OH)D increasing BMI are likely to be small. Population level interventions to reduce BMI are expected to decrease the prevalence of vitamin D deficiency.