title: Calcium supplementation increases blood creatinine concentration in a randomized controlled trial.
abstract: BACKGROUND
  Calcium supplements are widely used among older adults for osteoporosis prevention and treatment. However, their effect on creatinine levels and kidney function has not been well studied.
  
  
  METHODS
  We investigated the effect of calcium supplementation on blood creatinine concentration in a randomized controlled trial of colorectal adenoma chemoprevention conducted between 2004-2013 at 11 clinical centers in the United States. Healthy participants (N = 1,675) aged 45-75 with a history of colorectal adenoma were assigned to daily supplementation with calcium (1200 mg, as carbonate), vitamin D3 (1000 IU), both, or placebo for three or five years. Changes in blood creatinine and total calcium concentration were measured after one year of treatment and multiple linear regression was used to estimate effects on creatinine concentrations.
  
  
  RESULTS
  After one year of treatment, blood creatinine was 0.013±0.006 mg/dL higher on average among participants randomized to calcium compared to placebo after adjustment for other determinants of creatinine (P = 0.03). However, the effect of calcium treatment appeared to be larger among participants who consumed the most alcohol (2-6 drinks/day) or whose estimated glomerular filtration rate (eGFR) was less than 60 ml/min/1.73 m2 at baseline. The effect of calcium treatment on creatinine was only partially mediated by a concomitant increase in blood total calcium concentration and was independent of randomized vitamin D treatment. There did not appear to be further increases in creatinine after the first year of calcium treatment.
  
  
  CONCLUSIONS
  Among healthy adults participating in a randomized clinical trial, daily supplementation with 1200 mg of elemental calcium caused a small increase in blood creatinine. If confirmed, this finding may have implications for clinical and public health recommendations for calcium supplementation.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT00153816.
authors.affiliation: Department of Community and Family Medicine, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America.
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Barry
authors.affiliation: Department of Community and Family Medicine, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America.
authors.forename: Leila A
authors.initials: LA
authors.lastname: Mott
authors.affiliation: Departments of Medicine and of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, United States of America.
authors.forename: Michal L
authors.initials: ML
authors.lastname: Melamed
authors.affiliation: Department of Community and Family Medicine, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America.
authors.forename: Judith R
authors.initials: JR
authors.lastname: Rees
authors.affiliation: Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina, United States of America.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Ivanova
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sandler
authors.affiliation: Department of Veterans Affairs Eastern Colorado Health Care System and University of Colorado School of Medicine, Denver, Colorado, United States of America.
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Ahnen
authors.affiliation: Department of Gastroenterology, Hepatology and Nutrition, University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Bresalier
authors.affiliation: Department of Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Summers
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Roberd M
authors.initials: RM
authors.lastname: Bostick
authors.affiliation: Department of Community and Family Medicine, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America; Department of Medicine, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States of America; Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America.
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
mesh_terms: D000328:Adult; D000368:Aged; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002762:Cholecalciferol / Q000008:administration & dosage*; D003404:Creatinine / Q000097:blood*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000097:blood / Q000178:diet therapy* / Q000473:pathology
chemical_list: D002136:Calcium, Dietary; D002762:Cholecalciferol; D003404:Creatinine