CONTEXT Adequate vitamin D status for optimum bone health has received increased recognition in recent years; however, the ideal intake is not known. Serum 25-hydroxyvitamin D is the generally accepted indicator of vitamin D status, but no universal reference level has been reached. OBJECTIVE To investigate the relative importance of high calcium intake and serum 25-hydroxyvitamin D for calci...

BACKGROUND AND OBJECTIVES With an increased incidence of obesity in China, this study sought to investigate the correlation between serum 25-hydroxyvitamin D levels and adiposity phenotypes in Chinese adults from urban settings. METHODS AND STUDY DESIGN A total of 1277 subjects aged 20-82 years old were recruited into this cross-sectional study. Anthropometric parameters and blood biochemistr...

PURPOSE To investigate the association between blood 25-hydroxyvitamin D levels and pterygium. METHODS Korean National Health and Nutrition Examination Survey 2008-2011 were used for the present epidemiologic study. A total of 19,178 participants aged ≥ 30 years were evaluated for blood 25-hydroxyvitamin D levels and performed ophthalmic slit lamp examinations. Pterygium was considered as a g...

BACKGROUND Previous studies have reported an inverse association between vitamin D and childhood dental caries, but whether this is causal is unclear. OBJECTIVE To determine the causal effect of circulating 25-hydroxyvitamin D concentration on dental caries experience, early caries onset and the requirement for a dental general anesthetic. DESIGN A Mendelian randomization study was undertak...

BACKGROUND Vitamin D is not only important for bone health but can also affect the development of several non-bone diseases. The definition of vitamin D insufficiency by serum levels of 25-hydroxyvitamin D depends on the clinical outcome but might also be a consequence of analytical methods used for the definition. Although numerous 25-hydroxyvitamin D assays are available, their comparability ...

BACKGROUND Declining serum concentrations of 25-hydroxyvitamin D seen in the fall and winter as distance increases from the equator may be a factor in the seasonal increased prevalence of influenza and other viral infections. This study was done to determine if serum 25-hydroxyvitamin D concentrations correlated with the incidence of acute viral respiratory tract infections. METHODOLOGY/FINDI...

BACKGROUND Prediction of acute kidney transplant rejection remains imperfect despite several known risk factors. There is an increasing appreciation of the potential importance of the vitamin D pathway in immunological disease and transplantation. OBJECTIVE The purpose of this study was to determine the association of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D with acute rejection. DES...

We aimed to describe the vitamin D status of young women living in two Chinese cities in the spring--Beijing in the north (latitude 39 degrees north) and Hong Kong (latitude 22 degrees north) in the south. We also examined the relationship between serum 25-hydroxyvitamin D and parathyroid hormone (PTH) concentrations to determine a threshold for serum 25-hydroxyvitamin D above which there is no...

The decreased absorption of calcium by the small intestine of the adult may reflect changes in vitamin D metabolism with age. The purpose of this study was to compare the capacity of young (1.5 mo of age) and adult (12 mo of age) vitamin D-deficient rats to convert 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, the physiologically active form of vitamin D. Young rats responded to an oral dose ...

Simultaneous and accurate measurement of vitamin D and 25-hydroxyvitamin D in biological samples is a barrier limiting our ability to define "optimal" vitamin D status. Thus, our goal was to optimize conditions and evaluate an LC-MS method for simultaneous detection and quantification of vitamin D(2) , vitamin D(3) , 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) in serum. Extraction and sep...