title: Carbonated beverages and urinary calcium excretion.
abstract: BACKGROUND
  Intake of carbonated beverages has been associated with increased fracture risk in observational studies. The usual explanation given is that one or more of the beverage constituents increase urinary calcium.
  
  
  OBJECTIVE
  We assessed the short-term effects on urinary calcium excretion of carbonated beverages of various compositions.
  
  
  METHODS
  An incomplete random block design was used to study 20-40-y-old women who customarily consumed > or =680 mL carbonated beverages daily. Four carbonated beverages were tested: 2 with caffeine and 2 without. Two contained phosphoric acid as the acidulant and 2 contained citric acid. The study included one neutral control (water) and one positive control (skim or chocolate milk). Serving size was 567 mL for the carbonated beverages and water and 340 mL for the milks. Beverages were consumed with a light breakfast after an overnight fast; no other foods were ingested until urine collection was complete. pH, titratable and total acidity, sodium, creatinine, and calcium were measured in 2-h (morning) fasting and 5-h postbeverage urine specimens.
  
  
  RESULTS
  Relative to water, urinary calcium rose significantly only with the milks and the 2 caffeine-containing beverages. The excess calciuria was approximately 0.25 mmol, about the same as previously reported for caffeine alone. Phosphoric acid without caffeine produced no excess calciuria; nor did it augment the calciuria of caffeine.
  
  
  CONCLUSIONS
  The excess calciuria associated with consumption of carbonated beverages is confined to caffeinated beverages. Acidulant type has no acute effect. Because the caffeine effect is known to be compensated for by reduced calciuria later in the day, we conclude that the net effect of carbonated beverage constituents on calcium economy is negligible. The skeletal effects of carbonated beverage consumption are likely due primarily to milk displacement.
authors.affiliation: Creighton University Osteoporosis Research Center, Omaha, NE 68131, USA. rheaney@creighton.edu
authors.forename: R P
authors.initials: RP
authors.lastname: Heaney
authors.forename: K
authors.initials: K
authors.lastname: Rafferty
mesh_terms: D000328:Adult; D000818:Animals; D002110:Caffeine / Q000009:adverse effects*; D002118:Calcium / Q000378:metabolism / Q000652:urine*; D002253:Carbonated Beverages / Q000009:adverse effects / Q000032:analysis*; D019343:Citric Acid / Q000008:administration & dosage; D003404:Creatinine / Q000652:urine; D005215:Fasting; D005260:Female; D050723:Fractures, Bone / Q000209:etiology* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008892:Milk; D010756:Phosphoric Acids / Q000008:administration & dosage; D012307:Risk Factors; D012964:Sodium / Q000652:urine
chemical_list: D010756:Phosphoric Acids; D019343:Citric Acid; D002110:Caffeine; D012964:Sodium; D003404:Creatinine; C030242:phosphoric acid; D002118:Calcium