title: The impact of dietary calcium and oxalate ratios on stone risk.
abstract: OBJECTIVE
  To determine whether the ratio of dietary calcium and oxalate consumption at mealtime affects gastrointestinal oxalate absorption and urinary oxalate excretion.
  
  
  METHODS
  A study was conducted with 10 non-stone-forming adults placed on controlled diets with daily calcium and oxalate contents of 1000 and 750 mg, respectively. Subjects consumed a balanced calcium/oxalate ratio diet for 1 week, observed a minimum 1-week washout period, and subsequently consumed an imbalanced calcium/oxalate ratio diet for one week. Urine specimens were collected on the last 4 days of each diet. Outcome measures included urinary creatinine, calcium, and oxalate as well as the Tiselius index for assessing urinary calcium oxalate supersaturation.
  
  
  RESULTS
  Total daily calcium excretion, oxalate excretion, and Tiselius index were similar between balanced and imbalanced dietary phases. There were significant differences in calcium excretion (mg/g creatinine) between balanced and imbalanced diets in the 1-6 PM (83.1 vs 110.2, P <.04), 6-11 PM (71.3 vs 107.2, P <.02), and 11 PM-8 AM collections (55.0 vs 41.8, P <.02). There was significantly higher oxalate excretion on the balanced diet in the 1-6 pm time period (28.1 vs 16.7, P <.01). There were no differences in the Tiselius index in these collections.
  
  
  CONCLUSIONS
  These results demonstrate that the sequence of ingesting relatively large amounts of oxalate does not significantly affect calcium oxalate stone risk if the recommended daily quantity of dietary calcium is consumed.
authors.affiliation: Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
authors.forename: Jessica N
authors.initials: JN
authors.lastname: Lange
authors.forename: Kyle D
authors.initials: KD
authors.lastname: Wood
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Mufarrij
authors.forename: Michael F
authors.initials: MF
authors.lastname: Callahan
authors.forename: Linda
authors.initials: L
authors.lastname: Easter
authors.forename: John
authors.initials: J
authors.lastname: Knight
authors.forename: Ross P
authors.initials: RP
authors.lastname: Holmes
authors.forename: Dean G
authors.initials: DG
authors.lastname: Assimos
mesh_terms: D000328:Adult; D002129:Calcium Oxalate / Q000378:metabolism*; D002136:Calcium, Dietary / Q000652:urine; D003404:Creatinine / Q000652:urine; D004032:Diet; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D007669:Kidney Calculi / Q000737:chemistry / Q000453:epidemiology* / Q000378:metabolism; D008297:Male; D010070:Oxalates / Q000008:administration & dosage / Q000378:metabolism* / Q000652:urine
chemical_list: D002136:Calcium, Dietary; D010070:Oxalates; D002129:Calcium Oxalate; D003404:Creatinine