Vitamin D

BACKGROUND: The vitamin D-endocrine system is thought to play a role in physiologic processes that range from mineral metabolism to immune function. Serum 25-hydroxyvitamin D [25(OH)D] is the accepted biomarker for vitamin D status. Skin color is a key determinant of circulating 25(OH)D concentrations, and genes responsible for melanin content have been shown to be under strong evolutionary selection in populations living in temperate zones. Little is known about the effect of latitude on mean concentrations of 25(OH)D in dark-skinned populations...

BACKGROUND AND PURPOSE: Some recent studies in older, largely white populations suggest that vitamin D, measured by 25-hydroxyvitamin D [25(OH)D], is important for cognition, but such results may be affected by reverse causation. Measuring 25(OH)D in late middle age before poor cognition affects behavior may provide clearer results. METHODS: This was a prospective cohort analysis of 1652 participants (52% white, 48% black) in the Atherosclerosis Risk in Communities (ARIC) Brain MRI Study...

BACKGROUND: Low vitamin D status is associated with poorer cognitive function in older adults, but little is known about the potential impact on cerebrospinal fluid (CSF) biomarkers and brain volumes. The objective of this study was to examine the relations between plasma 25-hydroxyvitamin D (25(OH)D) and cognitive impairment, CSF biomarkers of Alzheimer's disease (AD), and structural brain tissue volumes. METHODS: A total of 75 patients (29 with subjective cognitive impairment, 28 with mild cognitive impairment, 18 with AD) referred to the Memory Clinic at Karolinska University Hospital, Huddinge, Sweden were recruited...

BACKGROUND: Deteriorated quality of life (QOL) is a major problem in osteoporotic women. However, little is known regarding the determinants of QOL in patients with osteoporosis. OBJECTIVE: Our aim was to explore the role of vitamin D status on QOL score in osteoporosis with high fracture risk. METHODS: Patients were osteoporotic women aged ≥70 years and with ≥1 risk factor for incident fracture, namely prevalent osteoporotic fracture, bone mineral density (BMD) >-3...

CONTEXT: Although vitamin D toxicity is rare in children, increased use of vitamin D formulations, re-examination of optimal vitamin D levels, and use of higher doses lend potential for an increased incidence of vitamin D toxicity. EVIDENCE ACQUISITION: A PubMed search was conducted through May 2013 for cases of vitamin D intoxication and vitamin D trials in pediatrics. Safety data were collected and reviewed. EVIDENCE SYNTHESIS: A small number of pediatric studies tested vitamin D doses at or above the currently recommended upper tolerable intake...

BACKGROUND: Prior research suggests that vitamin D protects against lung cancer only among certain subgroups. OBJECTIVES: We investigated whether vitamin D intake was associated with lung cancer and explored whether vitamin A intake modified the association. DESIGN: Prospective cohort data from 128,779 postmenopausal women, including 1771 incident lung cancers in the Women's Health Initiative (Clinical Trials and Observational Study) 1993-2010, were analyzed...

CONTEXT: Public health authorities around the world recommend widely variable supplementation strategies for adults, whereas several professional organizations, including The Endocrine Society, recommend higher supplementation. METHODS: We analyzed published randomized controlled clinical trials to define the optimal intake or vitamin D status for bone and extraskeletal health. CONCLUSIONS: The extraskeletal effects of vitamin D are plausible as based on preclinical data and observational studies...

IMPORTANCE: Vitamin D supplementation in infancy is required to support healthy bone mineral accretion. A supplement of 400 IU of vitamin D per day is thought to support plasma 25-hydroxyvitamin D (25[OH]D) concentrations between 40 and 50 nmol/L; some advocate 75 to 150 nmol/L for bone health. OBJECTIVE: To investigate the efficacy of different dosages of vitamin D in supporting 25(OH)D concentrations in infants. DESIGN, SETTING, AND PARTICIPANTS: Double-blind randomized clinical trial conducted among 132 one-month-old healthy, term, breastfed infants from Montréal, Québec, Canada, between March 2007 and August 2010...

The vitamin D signal transduction system involves a series of cytochrome P450-containing sterol hydroxylases to generate and degrade the active hormone, 1α,25-dihydroxyvitamin D3, which serves as a ligand for the vitamin D receptor-mediated transcriptional gene expression described in companion articles in this review series. This review updates our current knowledge of the specific anabolic cytochrome P450s involved in 25- and 1α-hydroxylation, as well as the catabolic cytochrome P450 involved in 24- and 23-hydroxylation steps, which are believed to initiate inactivation of the vitamin D molecule...

CONTEXT: Several trials have reported an increased risk of fractures and falls after intermittent high-dose vitamin D. Treatment with loading doses of vitamin D may increase 1,25(OH)(2) vitamin D catabolism through changes in calcium/phosphate homeostasis and fibroblast growth factor-23 (FGF-23). OBJECTIVE: The aim was to determine the effects of high-dose vitamin D on circulating concentrations of 1,25(OH)(2) vitamin D and FGF-23 in patients with osteoporosis and vitamin D insufficiency...

Significant controversy has emerged over the last decade concerning the effects of vitamin D on skeletal and nonskeletal tissues. The demonstration that the vitamin D receptor is expressed in virtually all cells of the body and the growing body of observational data supporting a relationship of serum 25-hydroxyvitamin D to chronic metabolic, cardiovascular, and neoplastic diseases have led to widespread utilization of vitamin D supplementation for the prevention and treatment of numerous disorders. In this paper, we review both the basic and clinical aspects of vitamin D in relation to nonskeletal organ systems...

OBJECTIVES: To identify participants' characteristics that influence the anti-fracture efficacy of vitamin D or vitamin D plus calcium with respect to any fracture, hip fracture, and clinical vertebral fracture and to assess the influence of dosing regimens and co-administration of calcium. DESIGN: Individual patient data analysis using pooled data from randomised trials. DATA SOURCES: Seven major randomised trials of vitamin D with calcium or vitamin D alone, yielding a total of 68 517 participants (mean age 69...

OBJECTIVES: To investigate the practicality and tolerability of high-dose intramuscular (i.m.) vitamin D2 or oral vitamin D3 replacement in vitamin D-insufficient patients, and to evaluate the biochemical efficacy of each formulation. METHODS: Sixty-nine patients with vitamin D insufficiency [25-hydroxyvitamin D (25(OH)D) <40 nmol/L] were recruited from the Rheumatology Outpatient Department of St George's Hospital, London. In study 1, 50 patients received 300 000 IU i...