title: Effects of Hydration and Calcium Supplementation on Urine Calcium Concentration in Healthy Postmenopausal Women.
abstract: OBJECTIVE
  The aim of this study was to determine whether calcium supplementation, compared with placebo, increases urine calcium concentrations to levels indicative of increased renal stone risk, and the role that fluid intake, as indicated by urine volume, may play in mitigating this risk.
  
  
  METHODS
  This is a secondary analysis of data from a randomized placebo-controlled trial of 500 mg/d calcium supplementation to prevent bone loss. Subjects were 240 white postmenopausal women age 40 to 70 years in good general health. Effects of supplementation on 1-year changes in 24h urine calcium concentration and urine volume were examined.
  
  
  RESULTS
  Both treatment group and urine volume were strong independent predictors of urine calcium concentration (p < 0.001). Among subjects with urine volume under 2 L/24 h, more than half of placebo subjects were at lowest risk for renal stones compared with less than 35% of calcium-supplemented subjects. Among those with higher urine volumes, all placebo subjects and more than 80% of calcium supplemented subjects were at lowest risk.
  
  
  CONCLUSIONS
  The increased risk of renal stones with calcium supplement use may be largely eliminated with adequate fluid intake, but older adults may not spontaneously consume adequate fluids to minimize this risk and should be counseled to do so.
authors: a Bone Metabolism Laboratory, USDA Jean Mayer Human Nutrition Research Center on Aging , Tufts University , Boston , Massachusetts.
authors: Susan S
authors: SS
authors: Harris
authors: Bess
authors: B
authors: Dawson-Hughes
mesh_terms: D000328:Adult; D000368:Aged; D002136:Calcium, Dietary / Q000009:adverse effects* / Q000627:therapeutic use / Q000652:urine; D003681:Dehydration / Q000150:complications* / Q000517:prevention & control; D019587:Dietary Supplements; D004326:Drinking; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007669:Kidney Calculi / Q000139:chemically induced*; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control* / Q000652:urine; D017698:Postmenopause; D012016:Reference Values; D014554:Urination; D014867:Water / Q000494:pharmacology*
chemical_list: D002136:Calcium, Dietary; D014867:Water
keywords: calcium supplements; hydration; renal stone risk; urine calcium concentration