The virtues of vitamin D-but how much is too much?

profile Rukshana Shroff, profile Craig Knott and profile Lesley Rees
Department of Nephrology, Great Ormond Street Hospital for Children, NHS Trust, Great Ormond Street, London, WC1N 3JH, UK, ShrofR at gosh.nhs.uk.
Pediatr Nephrol () (2010)
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. DOI: 10.1007/s00467-010-1499-9 * PMID: 20393752