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Purpose The objective of this study was to analyze vitamin D status and PTH concentrations in 6- to 8-year-old girls with central precocious puberty. Methods A cross-sectional clinical and blood testing study (calcium, phosphorus, 25(OH)D and PTH) was carried out in 78 girls with central precocious puberty (CPP group), aged 6.1–7.9 years. A control group was recruited (137 prepubertal girls, aged 6.1–8.2 years). The criteria of the US Endocrine Society were used for the defnition of hypovitaminosis D. Results There were no signifcant diferences in vitamin D status between both groups. There were no signifcant diferences in 25(OH)D concentrations between CPP (25.4±8.6 ng/mL) and control groups (28.2±7.4 ng/mL). In contrast, PHT concentrations in CPP group (44.8±16.3 pg/mL) were higher (p

The purpose of this study was to develop, test, and enhance a non-invasive clinical diagnostic screening tool for the identification of hypovitaminosis D, 25-hydroxyvitamin D [25(OH)D] serum levels 65 years from five long-term care communities in central Texas. A one-time venous blood draw measuring 25(OH)D serum level was obtained from each participant. Several multiple logistic regression models were tested to identify the best fitting model that described the relationship between categorical insufficient (30 ng/mL) serum levels correctly classified (specificity) and 90.00% of hypovitaminosis D correctly classified (sensitivity). Inter-reliability testing indicated that there was significant agreement between the two administered screeners (p

Background: Calciferol (vitamin D) is an essential nutrient that can be synthesized in the skin upon exposure to ultraviolet-B (UVB) light, or obtained through dietary and supplement sources. Traditionally known for its role in bone metabolism, vitamin D is currently described as a pleiotropic hormone with genomic and non-genomic roles in most body tissues. Clinical practice guidelines related to vitamin D are inconsistent and controversial. The purpose of this dissertation was to describe current patterns of vitamin D-related clinical care in a variety of settings, and to evaluate the impact of vitamin D supplements on the health and performance of collegiate athletes, a group with high prevalence of low vitamin D (LVD). Methods: This dissertation consists of five studies: 1) a scoping review of the health services literature related to clinical management of vitamin D; 2) a retrospective analysis of clinical care following non-indicated vitamin D testing using electronic health record (EHR) data from a regional health system; 3) a survey study to assess vitamin D-related practices among National Collegiate Athletic Association (NCAA) Division I programs; 4) an open clinical trial to evaluate the efficacy of a specific vitamin D supplement protocol in treating collegiate basketball athletes with LVD; and 5) a randomized, double-blind clinical trial to determine health and performance effects of vitamin D supplements in collegiate swimmers participating in fall season training. Results: Substantial inconsistency in vitamin D-related care was observed throughout the first three studies. Exponential increases in vitamin D testing and treatment, and associated costs, were identified in the U.S. and several other countries. A high proportion of this care was considered non-indicated (i.e., counter to professional guidelines). A lower rate of non-indicated vitamin D-related services was conducted within the health system we studied, but a cascade of low value services followed non-indicated vitamin D testing. Vitamin D testing was regularly performed by more than 65% of NCAA programs. In basketball athletes, 10 weeks of daily vitamin D3 supplements (5000 or 10,000 IU based on initial vitamin D status) improved serum 25-hydroxyvitamin D [25(OH)D], the common biomarker of vitamin D status. In swimmers, a vitamin D supplement protocol (5,000 IU vitamin D3 daily for 12 weeks) was efficacious in attenuating a seasonal decline in 25(OH)D compared with placebo. Swimmers taking vitamin D supplements also showed greater improvements in strength, power, and fat free mass. In both athlete studies, taking vitamin D supplements was associated with higher free testosterone concentration. Conclusions: The provision of evidence-based care related to vitamin D is complicated by contradictory clinical practice guidelines, resulting in inconsistent and sometimes, non-indicated care. Focused research on specific populations at high-risk for LVD can inform best practices. Our results suggest that taking vitamin D supplements is an efficacious strategy for athletes to improve 25(OH)D, especially when UVB exposure is low, and to enhance strength and power in collegiate swimmers.

Vitamin D is an essential fat-soluble nutrient that plays a critical role in calcium homeostasis among women of childbearing age. Vitamin D has also been linked to pregnancy health outcomes and may have long-term effects on maternal and child health. Nevertheless, the effects of human pregnancy on vitamin D requirements are poorly understood, and very little is known about placental vitamin D metabolism and its putative effects on maternal circulating pool of vitamin D. The impact of maternal vitamin D status on maternal and fetal bone health is also unclear. As such, my dissertation sought to advance understanding of vitamin D metabolism in human pregnancy, to characterize the effect of the placenta on maternal circulating vitamin D metabolites, and to examine the impact of maternal vitamin D status on maternal and fetal bone health. To achieve these aims, biomarkers of vitamin D status/metabolism were measured in blood and placental tissue obtained from third-trimester pregnant women who participated in a long-term controlled feeding study and consumed equivalent intakes of vitamin D, calcium, and phosphorus. A human placental cell culture model was also used to characterize vitamin D uptake, intracellular metabolism, secretion, and to inform the interpretation of the human study data. The data showed that pregnant women had 30-100% higher (P

Background: The association between vitamin D status and breast cancer risk is equivocal. No systematic reviews or meta-analyses have examined this association stratified by receptor status. Our objective is to conduct a systematic review to answer the question, “Is there a relationship between lower serum/plasma vitamin D levels and increased risk of triple negative breast cancer (TNBC) specifically?”Methods: We system searched Embase and PubMed databases for published original research studies examining the risk of a breast cancer diagnosis according to vitamin D status. We excluded studies that did not provide risk estimates stratified by receptor status.Results: Fourteen studies met our criteria, including case-control, nested case-control, and case-series studies, reflecting the cumulative results of 13,135 breast cancer cases. When grouped by relevancy to TNBC, the proportion of analyses across all study types showing a significant association between vitamin D status and breast cancer diagnosis was 37% for non-TNBC analyses, 48% for analyses that included some TNBC cases, and 88% for TNBC analyses. Conclusions: Our results suggest that low vitamin D status may particularly increase the risk of TNBC, although more research is needed to determine if this association is causative. Women should be routinely screened for 25(OH)D deficiency.

Background: There are limited data regarding the prevalence and risk factors relating to hypovitaminosis D in children of Thailand, a tropical country with abundant sunlight. The objective of this study was to assess the prevalence of hypovitaminosis D and examine factors associated with hypovitaminosis D in school-aged children in Bangkok, Thailand – a centrally located capital city. Methods: This cross-sectional study evaluated 159 healthy children (33.3% boys and 66.7% girls), aged 6 to 12 years, in Bangkok, Thailand (located at 13.45°N). Fasting plasma samples were examined for total 25-hydroxyvitamin D [25(OH)D] using electrochemiluminescence immunoassay. Demographic characteristics (age, sex, household income), past medical history (birth weight, allergic diseases, hospitalization), amount of sun exposure, anthropometric data, and selected biochemical tests were used to investigate for factors associated with hypovitaminosis D. Results: Overall, the mean ± SD level of plasma 25(OH)D was 64.0 ± 15.1 nmol/L. Hypovitaminosis D (< 75 nmol/L) was presented in 79.2% of subjects. Of these, the prevalence of vitamin D insufficiency and vitamin D deficiency were 59.7% and 19.5%, respectively. In univariate analysis, children with hypovitaminosis D (< 75 nmol/L) had a higher mean body mass index (BMI) percentile than the vitamin D-sufficient group (56.7 ± 33.9 vs. 42.6 ± 36.0; P-value = 0.04). Plasma PTH levels in the children with hypovitaminosis D were significantly higher than in the children with normal levels of vitamin D (4.34 ± 1.38 vs 3.78 ± 1.25 pmol/L; P-value = 0.04). In multivariate analysis, high BMI percentile and high PTH concentration were the parameters associated with 25(OH)D level < 75 nmol/L. Conclusion: The prevalence of hypovitaminosis D in healthy Thai children is very high, despite their exposure to sunlight, and that prevalence increases in children with a high BMI percentile. As a result, a formal recommendation for vitamin D supplementation in Thai children should be considered.

Low vitamin D blood levels are postulated to be a risk factor for worse lung function, largely based on cross-sectional data. We sought to use longitudinal data to test the hypothesis that baseline plasma 25-hydroxyvitamin D [25(OH)D] is lower in subjects with more rapid lung function decline, compared to those with slow lung function decline. We conducted a nested, matched case-control study in the Lung Health Study 3 cohort. Cases and controls were continuous smokers with rapid and slow lung function decline, respectively, over approximately 6 years of follow-up. We compared baseline 25(OH)D levels between cases and controls, matching on date of blood draw and clinical center. Among 196 subjects, despite rapid and slow decliners experiencing strikingly and significantly different rates of decline of forced expiratory volume in one second (-152 vs. -0.3 mL/year; p

Vitamin D, a pleiotropic hormone essential for calcium homeostasis, has generated widespread interest due to associations with numerous health outcomes. Cross-sectional studies of vitamin D and lung function reported strong, positive associations, but representative, longitudinal population-based studies are lacking, and biological mechanisms are unclear. Lung function decline is the primary characteristic of chronic obstructive pulmonary disease (COPD), the 3rd leading cause of mortality in the United States; given limited treatments to delay progression, identifying preventative approaches is critical. This work aims to elucidate determinants of vitamin D status, and investigate the role of vitamin D as a determinant of lung function. First, we explored genetic and non-genetic determinants of serum vitamin D [25(OH)D] in African Americans. Approximately 25% of 25(OH)D variability was explained by non-genetic factors, and multivitamin supplement use was the strongest predictor. A single nucleotide polymorphism (SNP) in the vitamin D binding protein modified the effect of multivitamin supplement use on 25(OH)D. About 23% of 25(OH)D variability was estimated to be attributable to genetic variation, with replication in a separate cohort. However, the influence of genetic ancestry made an exact estimate impossible; further exploration of genetic determinants of 25(OH)D in African Americans is needed. Second, potential mechanisms for vitamin D-lung health associations were explored through a cross-sectional study of SNPs in 13 candidate vitamin Dresponsive genes. SNPs in SGPP2, a phosphatase in the sphingosine-1-phosphate signaling pathway, were associated with lung function and COPD risk. Further, we identified an association between SNPs in SGPP2 and lung-tissue specific expression of SGPP2. While specific mechanisms remain to be investigated, SGPP2 is a promising vitamin D-responsive candidate gene. Finally, associations between variants in vitamin D metabolic genes, serum 25(OH)D and lung function were explored in the Framingham Heart Study. SNPs in four vitamin D metabolic genes were associated with rate of change in FEV1, but there was no association between 25(OH)D and rate of change in FEV1 in the Third Generation cohort, a group of largely vitamin D sufficient middleaged adults. Future studies should consider the influence of baseline nutritional status and underlying genetic variation on vitamin D-disease associations.

The aim of this cross-sectional study was to investigate the relationship between vitamin D status and laboratory measures that are relevant to physical performance in competitive ice hockey players. Data was collected for 53 junior and collegiate ice hockey players residing near Minneapolis, Minnesota (44.9� N) during the offseason (May 16-June 28). Vitamin D status was inversely associated with percent body fat and positively associated with handgrip strength, trended with peak power during the wingate test, but not with vertical jump height after adjusting for measured covariates. Representing a novel finding of this study, 25(OH)D status was inversely related to jump execution time, time to peak power and positively associated with force gradient during the squat jump after adjusting for potential covariates.

Background: It is not known whether genetic variation in the vitamin D binding protein (DBP) influences 25-hydroxyvitamin D levels [25(OH)D] after vitamin D supplementation. We aimed to investigate the changes of total 25(OH)D, 25(OH)D3 and 25(OH)D2 in a Thai cohort, according to type of vitamin D supplement (vitamin D3 or D2) and DBP genotype, after receiving vitamin D3 or D2 for 3 months. Methods: Thirty-nine healthy subjects completed the study. All subjects received 400 IU of either vitamin D3 or D2, plus a calcium supplement, every day for 3 months. Total serum 25(OH)D, 25(OH)D3 and 25(OH)D2 were measured by LC-MS/MS. Individual genotyping of rs4588 in the DBP gene was performed using real-time PCR. Results: Vitamin D3 supplementation of 400 IU/d increased 25(OH)D3 significantly (+16.2 ± 4.2 nmol/L, p

Background: Existing inconclusive data on the relationship between vitamin D status and human glucose homeostasis suggests that other factors, such as adiposity, might influence this relationship. The present study aimed to investigate the association between 25-hydroxyvitamin D [25(OH)D] and fasting plasma glucose (FPG) in the context of different amounts of total body fat in a healthy community-based population in Bangkok, Thailand. Methods: This cross-sectional study was a part of health survey of employees of the Electricity Generating Authority of Thailand. There were 1,990 healthy subjects (72.8% male) in this study. Total body fat was measured by bioelectrical impedance analysis. Total serum 25(OH)D, 25(OH)D3 and 25(OH)D2 were measured by LC-MS/MS. Results: Age (r = 0.134, p < 0.001) and FPG (r = 0.089, p < 0.001) were positively correlated with 25(OH)D levels, while total body fat mass (r = −0.049, p = 0.03) were negatively correlated with 25(OH)D levels. 25(OH)D levels were higher in males than in females (65.0 ± 0.5 vs. 53.5 ± 0.5 nmol/L, p < 0.001). After controlling for age, gender and total fat mass, FPG was no longer correlated with 25(OH)D. However, when subjects were stratified according to fat-free mass tertiles and controlled for age and gender, there was a positive, although weak association between 25(OH)D levels and FPG (p = 0.01) in the lowest tertile. Conclusions: We therefore speculate that adiposity might influence the relationship of vitamin D status and FPG.

Background: Determinants of vitamin D status are of interest when studying the epidemiology of disease in population groups because vitamin D is now recognized to decrease the risk of diseases such as osteoporosis, cancer, and cardiovascular disease. Understanding modifiable determinants of vitamin D status are important for managing vitamin D deficiency at the individual level and for addressing this issue at population level. Objective: The objective of this study was to evaluate the associations between serum vitamin D status (deficiency and insufficiency) and distinct demographic, dietary, and lifestyle characteristics of adults in the United States using a large, nationally representative sample survey, the National Health and Nutrition Examination Survey (NHANES) 2005-2006. Methods: The study sample consisted of 2340 adults aged 20-59 who had serum 25(OH)D measured and who had completed various questionnaires concerning dietary intake of vitamin D and other lifestyle factors. Multivariate logistic regression was used to estimate the odds ratio (OR) of vitamin D deficiency, insufficiency, and sufficiency in adults based on distinct demographic, dietary, and lifestyle characteristics. Statistical significance was set at α < 0.05. Results: The prevalence of vitamin D deficiency was higher in obese adults than in underweight to normal weight adults (50.9% ± 4.57 vs. 29.3% ± 3.57), higher in adults who reported no sunburns than in adults who reported ≥ 3 sunburns (49.9% ± 3.82 vs. 18.0% ± 3.07), and higher in adults who use sun protective measures regularly than in adults who do not (48.4% ± 3.93 vs. 27.0% ± 3.75). The prevalence of vitamin D deficiency increased as dietary intake of vitamin D decreased. Non-Hispanic black adults were significantly more likely to be vitamin D deficient (OR = 45.27, 95% CI = 17.27-118.64) and insufficient (OR = 9.37, 95% CI = 3.43-25.61) than non-Hispanic white adults. Significant positive associations were found between vitamin D deficiency and several characteristics, namely obesity (OR = 7.43, 95% CI = 4.33-12.77), physical inactivity (OR = 1.63, 95% CI = 1.03-2.58) poor dietary vitamin D intake (OR = 2.34, 95% CI = 1.44-3.81), non-supplement use or supplement use with a low amount of vitamin D (OR = 1.75, 95% CI = 1.05-2.89), and activities that decrease exposure to sunlight (from OR = 2.97, 95% CI = 2.14-4.13 to OR = 5.30, 95% CI = 3.17-8.85). Conclusion: The results of this nationally representative study demonstrate that obesity, physical inactivity, poor dietary intake of vitamin D, and low sunlight exposure increases the risk for vitamin D deficiency in U.S adults. Future studies are needed to investigate whether vitamin D supplementation, sunlight exposure, and vitamin D-fortified foods are efficient in correcting vitamin D deficiency and insufficiency among these groups.

Abstract: Consumer acceptance of meat depends on its colour and there is a negative bias in North America for broiler dark meat. Freezing and cooking leads to changes in meat characteristics and colour of broiler chicken thighs. The first experiment focused on the effect of freezing and cooking on broiler thighs and comparisons with fresh uncooked thighs. Freezing and cooking resulted in pigment leakage from bones and meat heme pigment oxidation and denaturation. The meat colour was not dark under the applied conditions. The second experiment dealt with the effect of diet (vitamin D, 25-hydroxyvitamin D3, dilute) fed to broilers (Male Ross 308) on the meat characteristics and colour differences in broiler thighs. The study revealed that bones from birds fed 25-hydroxyvitamin D3 diet may have a better bone mineralization indicated by certain meat parameters. However the color of meat was not affected by the dietary treatments.