title: The virtues of vitamin D--but how much is too much?
abstract: Vitamin D deficiency is common in healthy adults and children as well as in the chronic kidney disease (CKD) population. What was once a disease of malnourished children in the developing world has re-emerged and reached pandemic proportions. In parallel with this development, there is a growing awareness that vitamin D is not simply a 'calcaemic hormone' but plays an important role in the prevention of cardiovascular disease, infectious and auto-immune conditions, renoprotection, glycaemic control and prevention of some common cancers. Most tissues in the body have a vitamin D receptor and the enzymatic machinery to convert 'nutritional' 25-hydroxyvitamin D to the active form 1,25-dihydroxyvitamin D; it is estimated that 3% of the human genome is regulated by the vitamin D endocrine system. Although there are few well-conducted studies on the benefits of vitamin D therapy, an exuberant use of vitamin D is now seen in the general population and at all stages of CKD. There is emerging evidence that vitamin D may in fact have a therapeutic window, and at least from the effects on the cardiovascular system, more is not necessarily better. In this review, we discuss the role of nutritional vitamin D (ergocalciferol or cholecalciferol) supplementation in CKD patients, interpreting the clinical studies in the light of the vitamin D metabolic pathway and its pluripotent effects. While nutritional vitamin D compounds clearly have numerous beneficial effects, randomised controlled studies are required to determine the effectiveness and optimal dose at different stages of CKD, its concurrent use with activated vitamin D compounds and its safety profile.
authors.affiliation: Department of Nephrology, Great Ormond Street Hospital for Children, NHS Trust, Great Ormond Street, London WC1N 3JH, UK. ShrofR@gosh.nhs.uk
authors.forename: Rukshana
authors.initials: R
authors.lastname: Shroff
authors.forename: Craig
authors.initials: C
authors.lastname: Knott
authors.forename: Lesley
authors.initials: L
authors.lastname: Rees
mesh_terms: D019587:Dietary Supplements / Q000009:adverse effects; D006706:Homeostasis; D006801:Humans; D007674:Kidney Diseases / Q000188:drug therapy / Q000378:metabolism*; D018673:Nutrition Policy; D018167:Receptors, Calcitriol / Q000378:metabolism; D015398:Signal Transduction; D016896:Treatment Outcome; D014807:Vitamin D / Q000009:adverse effects / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000188:drug therapy / Q000378:metabolism*; D014815:Vitamins / Q000009:adverse effects
chemical_list: D018167:Receptors, Calcitriol; D014815:Vitamins; D014807:Vitamin D
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