We summarize the key findings, strength of the evidence, and research needs identified in the National Institutes of Health conference "Vitamin D and Health in the 21st Century: an Update," which was held in September 2007; a systematic evidence-based review; and a National Institutes of Health roundtable discussion held after the conference by scientists with relevant expertise. The evidence-based review addressed 5 questions on 25-hydroxyvitamin D [25(OH)D] and functional outcomes across the life cycle and response to exposure, bone health outcomes of supplementation, risks and benefits of sun exposure, and adverse outcomes. These questions also framed the conference and roundtable discussions. Researchers have made considerable progress in understanding the relation of 25(OH)D to bone health outcomes in the elderly and in postmenopausal women, but we know less about its impact on other stages of the life cycle and in racial and ethnic groups. Limitations of the existing data include the failure of many studies to control for important confounders [baseline 25(OH)D concentration, skin pigmentation, body mass index, compliance, etc], sparse data on key vulnerable populations (dark-skinned persons, reproducing women, infants, children, and adolescents), problems of accuracy and excessive variability in measuring 25(OH)D, lack of established relation of 25(OH)D with functional outcomes except in the elderly, and limited information on the effects of vitamin D independent of calcium, magnesium, and phosphate. Future research should determine and validate across the life cycle relevant functional outcomes for bone and other health factors as well as adverse outcomes for the biomarker of exposure, 25(OH)D, to enable assessment of the role of vitamin D status in health maintenance and disease prevention.
"Cholecalciferol, or vitamin D3, is synthesized from 7-dehydrocholesterol in the skin by sunlight. The vitamin undergoes two consecutive hydroxylations, one in the liver to 25(OH)D (the inactive form of vitamin D) and the other in the kidneys to 1,25(OH)D, its active form, by the enzyme 1a hydroxylase  . Studies have demonstrated a role of vitamin D in enhanced eradication of intracellular pathogens like Mycobacterium tuberculosis , killing of a number of antibiotic-resistant bacteria , viruses and Chlamydia   and vitamin D deficiency may contribute to chronic respiratory infection and airway colonization . "
[Show abstract][Hide abstract] ABSTRACT: Vitamin D deficiency is prevalent among patients with chronic obstructive pulmonary disease (COPD) and comes to be more frequent with increased disease severity. We aimed to assess the role of vitamin D supplementation in patients with severe COPD.
"Additional adverse pregnancy outcomes that have been linked to maternal vitamin D deficiency include an increased incidence of low birth weight babies, and an increased risk for gestational diabetes , preterm delivery, obstructed labor, cesarean delivery, and miscarriage in some, but not all, studies (Brannon et al., 2008; Bodnar et al., 2009; Dror and Allen, 2010; Dror et al., 2011; Hollis et al., 2011; Lau et al., 2011; Poel et al., 2012; Thorne-Lyman and Fawzi, 2012; Wei et al., in press). Genetic variability of the VDR has been strongly associated with infant birth weight among non-Hispanic black (who have higher rates of preterm birth and low birth weight infants), but not non-Hispanic white, women (Swamy et al., 2011). "
"It is a moot point whether adiposity, which is increasingly prevalent in people with advanced age , may also negatively impact the vitamin D status in the elderly. Numerous studies have linked low 25-hydroxyvitamin D levels [25(OH)D], the commonly used indicator of the vitamin D status , with obesity [7-21], whereas other researchers have failed to confirm this observation [22-24]. There are some limitations of these previous studies. "
[Show abstract][Hide abstract] ABSTRACT: Background
Emerging evidence indicates that there is an association between vitamin D and obesity. The aim of this study was to investigate whether the level of serum 25-hydroxyvitamin D3 [25(OH)D3] in the elderly is influenced by parameters of anthropometry and body composition independent of potential confounding lifestyle factors and the level of serum intact parathyroid hormone (iPTH).
Cross-sectional data of 131 independently living participants (90 women, 41 men; aged 66–96 years) of the longitudinal study on nutrition and health status in senior citizens of Giessen, Germany were analysed. Concentrations of 25(OH)D3 and iPTH were ascertained by an electrochemiluminescence immunoassay. Body composition was measured by a bioelectrical impedance analysis. We performed univariate and multiple regression analyses to examine the influence of body composition on 25(OH)D3 with adjustments for age, iPTH and lifestyle factors.
In univariate regression analyses, 25(OH)D3 was associated with body mass index (BMI), hip circumference and total body fat (TBF) in women, but not in men. Using multiple regression analyses, TBF was shown to be a negative predictor of 25(OH)D3 levels in women even after controlling for age, lifestyle and iPTH (ß = −0.247; P = 0.016), whereas the associations between BMI, hip circumference and 25(OH)D3 lost statistical significance after adjusting for iPTH. In men, 25(OH)D3 was not affected by anthropometric or body composition variables.
The results indicate that 25(OH)D3 levels are affected by TBF, especially in elderly women, independent of lifestyle factors and iPTH.
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