Vitamin D

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  1. Blackmore KM, Lesosky M, Barnett H, et al. Vitamin D From Dietary Intake and Sunlight Exposure and the Risk of Hormone-Receptor-Defined Breast Cancer. Am J Epidemiol. 2008 Oct 15; 168(8):915-24.



http://aje.oxfordjournals.org/content/168/8/915.long

 

*Quick Summary of Study: This epidemiological study investigate the association between vitamin D intake at specific ages and the prevalence of combined estrogen- receptor and progesterone-receptor defined breast cancer in woman living in Ontario Canada.

 

Abstract

“Evidence has emerged for a role of vitamin D in the development of breast cancer, and there is some suggestion that its antiproliferative effect is greater in hormone-receptor-positive cells. Few epidemiologic studies have considered the association between vitamin D and hormone-receptor-defined breast cancer, and the results are conflicting. Considering 759 cases and 1,135 controls from a case-control study (Ontario, Canada, 2003-2005), the authors examined the association between vitamin D intake at specific ages and combined estrogen-receptor- (ER) and progesterone-receptor- (PR) defined breast cancer. While increased intake of vitamin D (from the sun and diet) was most consistently associated with a significantly reduced risk of ER+/PR+ tumors (e.g., odds ratio = 0.76, 95% confidence interval: 0.59, 0.97 for use of cod liver oil during adolescence), comparable nonsignificant associations were found for receptor-negative (ER-/PR-) (odds ratio = 0.74, 95% confidence interval: 0.53, 1.04) and mixed (ER+/PR-) (odds ratio = 0.79, 95% confidence interval: 0.51, 1.22) tumors. This study suggests that vitamin D is associated with a reduced risk of breast cancer regardless of ER/PR status of the tumor. Future studies with a larger number of receptor-negative and mixed tumors are required.”(1)



  1. Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004 Dec; 80(6 Suppl):1678S-88S.



http://www.ajcn.org/content/80/6/1678S.long

 

*Quick Summary of Study: This article explains the essential role that vitamin D has on human health and explains how increasing deficiencies from lack of sun exposure and dietary inadequacies can lead to certain ailments.

 

Abstract

“Most humans depend on sun exposure to satisfy their requirements for vitamin D. Solar ultraviolet B photons are absorbed by 7-dehydrocholesterol in the skin, leading to its transformation to previtamin D3, which is rapidly converted to vitamin D3. Season, latitude, time of day, skin pigmentation, aging, sunscreen use, and glass all influence the cutaneous production of vitamin D3. Once formed, vitamin D3 is metabolized in the liver to 25-hydroxyvitamin D3 and then in the kidney to its biologically active form, 1,25-dihydroxyvitamin D3. Vitamin D deficiency is an unrecognized epidemic among both children and adults in the United States. Vitamin D deficiency not only causes rickets among children but also precipitates and exacerbates osteoporosis among adults and causes the painful bone disease osteomalacia. Vitamin D deficiency has been associated with increased risks of deadly cancers, cardiovascular disease, multiple sclerosis, rheumatoid arthritis, and type 1 diabetes mellitus. Maintaining blood concentrations of 25-hydroxyvitamin D above 80 nmol/L (approximately 30 ng/mL) not only is important for maximizing intestinal calcium absorption but also may be important for providing the extrarenal 1alpha-hydroxylase that is present in most tissues to produce 1,25-dihydroxyvitamin D3. Although chronic excessive exposure to sunlight increases the risk of nonmelanoma skin cancer, the avoidance of all direct sun exposure increases the risk of vitamin D deficiency, which can have serious consequences. Monitoring serum 25-hydroxyvitamin D concentrations yearly should help reveal vitamin D deficiencies. Sensible sun exposure (usually 5-10 min of exposure of the arms and legs or the hands, arms, and face, 2 or 3 times per week) and increased dietary and supplemental vitamin D intakes are reasonable approaches to guarantee vitamin D sufficiency.”(2)

 

  1. Holick MFChen TC. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr. 2008 Apr; 87(4):1080S-6S.

http://www.ajcn.org/content/87/4/1080S.long

 

*Quick Summary of Study: This article explains the growing concern over vitamin D deficiencies and how these deficiencies are associated with increased risk of several diseases such as osteopenia, autoimmune disorders and certain cancers.

 

ABSTRACT

“Vitamin D deficiency is now recognized as a pandemic. The major cause of vitamin D deficiency is the lack of appreciation that sun exposure in moderation is the major source of vitamin D for most humans. Very few foods naturally contain vitamin D, and foods that are fortified with vitamin D are often inadequate to satisfy either a child's or an adult's vitamin D requirement. Vitamin D deficiency causes rickets in children and will precipitate and exacerbate osteopenia, osteoporosis, and fractures in adults. Vitamin D deficiency has been associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases. A circulating level of 25-hydroxyvitamin D of >75 nmol/L, or 30 ng/mL, is required to maximize vitamin D's beneficial effects for health. In the absence of adequate sun exposure, at least 800–1000 IU vitamin D3/d may be needed to achieve this in children and adults. Vitamin D2may be equally effective for maintaining circulating concentrations of 25-hydroxyvitamin D when given in physiologic concentrations.”(3)

 

  1. Hayes CE, Nashold FE, Spach KM, Pedersen LB. The immunological functions of the vitamin D endocrine system. Cell Mol Biol. 2003; 49(2):277-300. 

 

http://www.ncbi.nlm.nih.gov/pubmed/12887108?dopt=Abstract

 

*Quick Summary of Study: This review articles focuses on role that vitamin D plays in the immune system; from the mechanism in which vitamin D may activate certain white blood cells, to its role in regulating inflammation and clearing mycobacterial infections, as well as its role with the endocrine system in establishing self-tolerance and possibly prevention of auto-immune diseases.

 

Abstract

“The discoveries that activated macrophages produce 1alpha25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3), and that immune system cells express the vitamin D receptor (VDR), suggested that the vitamin D endocrine system influences immune system function. In this review, we compare and contrast how 1alpha,25-(OH)2D3 synthesis and degradation is regulated in kidney cells and activated macrophages, summarize data on hormone receptor function and expression in lymphocytes and myeloid lineage cells, and discuss how locally-produced 1alpha,25-(OH)2D3 may activate a negative feed-back loop at sites of inflammation. Studies of immunity in humans and animals lacking VDR function, or lacking vitamin D, are viewed to gain insight into the immunological functions of the vitamin D endocrine system. The strong associations between poor vitamin D nutrition, particular VDR alleles, and susceptibility to chronic mycobacterial infections, together with evidence that 1alpha,25-(OH)2D3 served as a vaccine adjuvant enhancing antibody-mediated immunity, suggest a model wherein high levels of 1alpha,25-(OH)2D3-liganded VDR transcriptional activity may promote the CD4+ T helper 2 (Th2) cell-mediated and mucosal antibody responses to cutaneous antigens in vivo. We also review a diverse and rapidly growing body of epidemiological, climatological, genetic, nutritional and biological evidence indicating that the vitamin D endocrine system functions in the establishment and/or maintenance of immunological self tolerance. Studies done in animal models of multiple sclerosis (MS), insulin-dependent diabetes mellitus (IDDM), inflammatory bowel disease (IBD), and transplantation support a model wherein the 1alpha,25-(OH)2D3 may augment the function of suppressor T cells that maintain self tolerance to organ-specific self antigens. The recent progress in infectious disease, autoimmunity and transplantation has stimulated a gratifying renaissance of interest in the vitamin D endocrine system and its role in immunological health.”(4)

  1. Lin R, White JH. The pleiotropic actions of vitamin D. Bioessays. 2004; 26(1):21-28.

          http://www.ncbi.nlm.nih.gov/pubmed/14696037?dopt=Abstract

Abstract

“General knowledge of the role of vitamin D3 in human physiology has been shaped by its discovery as a preventive agent of nutritional rickets, a defect in bone development due to inadequate uptake of dietary calcium. Studies on the function of the hormonal form of vitamin D3, 1alpha,25-dihydroxyvitamin D3, have been greatly accelerated by the molecular cloning and structural analysis of the vitamin D3 receptor, which is a ligand-activated regulator of gene transcription. Molecular genetic techniques including genomics have helped reveal that 1alpha,25-dihydroxyvitamin D3 can control more than calcium homeostasis. It has widespread effects on cellular differentiation and proliferation, and can modulate immune responsiveness, and central nervous system function. Moreover, accumulating epidemiological and molecular evidence suggests that 1alpha,25-dihydroxyvitamin D3 acts as a chemopreventive agent against several malignancies including cancers of the prostate and colon. Here, we survey the most-recent findings and discuss their implications for the potential therapeutic uses of vitamin D analogues.”[5]

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