Table 2.

Urinary calcium as a fraction of calcium intake for each cohort

Stone FormersNonstone FormersUrinary Ca2+ ≥ Cohort MedianUrinary Ca2+ < Cohort Median
HPFS (n = 1037)
    urinary Ca2+ (mg/d)194a156255c121
    urinary/dietary Ca2+ intake27%a19%36%c15%
    urinary/total Ca2+ intake22%a16%31%c13%
NHS I (n = 1246)
    urinary Ca2+ (mg/d)188b170252c116
    urinary/dietary Ca2+ intake25%b21%38%c16%
    urinary/total Ca2+ intake16%a12%22%c10%
NHS II (n = 1085)
    urinary Ca2+ (mg/d)204a171262c141
    urinary/dietary Ca2+ intake25%a18%33%c16%
    urinary/total Ca2+ intake18%a13%22%c11%
  • Values are medians. Urinary/dietary Ca2+ values are calculated only in participants not taking calcium supplements (HPFS, n = 538; NHS I, n = 386; and NHS II, n = 398).

  • a P values <0.01 comparing stone formers to non-stone formers.

  • b P values <0.05 comparing stone formers to non-stone formers.

  • c P values <0.01 comparing high to low urinary Ca2+.