title: Vitamin D supplementation in chronic kidney disease: a systematic review and meta-analysis of observational studies and randomized controlled trials.
abstract: OBJECTIVE
  Vitamin D deficiency is highly prevalent among patients with chronic kidney disease (CKD). The benefits and harms of vitamin D supplementation (ergocalciferol or cholecalciferol) were assessed in patients with nondialysis-dependent CKD, dialysis-dependent CKD, and renal transplant recipients.
  
  
  METHODS
  MEDLINE (1966 to September 2009), SCOPUS (September 2009), and nephrology conference proceedings were searched for relevant observational and randomized controlled trials (RCTs). Treatment effects were summarized as mean differences (MDs) with 95% confidence intervals (CIs) using a random effects model. Separate analyses were conducted for observational studies and RCTs.
  
  
  RESULTS
  Twenty-two studies (17 observational and 5 RCTs) were included. There was a significant improvement in 25-hydroxyvitamin D (MD 24.1 ng/ml, 95% CI 19.6 to 28.6) and an associated decline in parathyroid hormone (PTH) levels (MD -41.7 pg/ml, 95% CI -55.8 to -27.7) among observational studies. PTH reduction was higher in dialysis patients. Among RCTs, there was a significant improvement in 25-hydroxyvitamin D (MD 14 ng/ml, 95% CI 5.6 to 22.4) and an associated decline in PTH levels (MD -31.5 pg/ml, 95% CI -57 to -6.1). A low incidence of hypercalcemia and hyperphosphatemia was reported with vitamin D supplementation. Cardiovascular and skeletal effects of vitamin D supplementation have not been studied. Included studies were mostly of low to moderate quality.
  
  
  CONCLUSIONS
  Available evidence from low-to-moderate quality observational studies and fewer RCTs suggests that vitamin D supplementation improves biochemical endpoints. However, whether such improvements translate into clinically significant outcomes is yet to be determined.
authors.affiliation: Department of Nephrology, Indiana University, Indianapolis, Indiana, USA.
authors.forename: Praveen
authors.initials: P
authors.lastname: Kandula
authors.forename: Mirela
authors.initials: M
authors.lastname: Dobre
authors.forename: Jesse D
authors.initials: JD
authors.lastname: Schold
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Schreiber
authors.forename: Rajnish
authors.initials: R
authors.lastname: Mehrotra
authors.forename: Sankar D
authors.initials: SD
authors.lastname: Navaneethan
mesh_terms: D002118:Calcium / Q000097:blood; D002908:Chronic Disease; D019587:Dietary Supplements; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood; D007674:Kidney Diseases / Q000097:blood*; D007676:Kidney Failure, Chronic / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood; D010758:Phosphorus / Q000097:blood; D016032:Randomized Controlled Trials as Topic; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; D010758:Phosphorus; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; C104450:25-hydroxyvitamin D; D002118:Calcium