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Table 1 Characteristics of the participants in the main cohort and the sub-study

From: Increased calcium intake is associated lower serum 25-hydroxyvitamin D levels in subjects with adequate vitamin D intake: a population-based observational study

  All subjects Males Females
Main cohorta
 N 11,250 5268 5982
 Age (years) 58.3 (58.1, 58.5) 58.5 (58.2, 58.8) 58.0 (57.7, 58.3)*
 BMI (kg/m2) 27.3 (27.2, 27.4) 27.7 (27.6, 27.8) 26.9 (26.8, 27.1)***
 Serum 25(OH)D (nmol/L) 62.2 (62.0, 62.7) 59.2 (58.7, 59.8) 65.1 (64.5, 65.6)***
 Vitamin D intake (ug/d)c 14.1 (14.0, 14.3) 14.5 (14.2, 14.7) 13.9 (13.6, 14.1)**
 Calcium intake (mg/d)c 1188 (1177, 1199) 1247 (1231, 1264) 1136 (1121, 1151)***
Sub-studyb
 N 1917 828 1089
 Age (years) 70.2 (69.8, 70.6) 70.7 (70.3, 71.3) 69.9 (69.3, 70.4)
 BMI (kg/m2) 27.4 (27.2, 27.6) 27.6 (27.3, 27.8) 27.4 (27.1, 27.6)
 Serum 25(OH)D (nmol/L) 68.2 (67.3, 69.2) 65.3 (64.0, 66.7) 70.4 (69.2, 71.7)***
 Serum PTH (pmol/L) 5.8 (5.7, 5.9) 5.9 (5.7, 6.0) 5.8 (5.7, 5.9)
 Serum calcium (mmol/L) 2.36 (2.36, 2.36) 2.35 (2.35, 2.36) 2.37 (2.36, 2.37)***
 Vitamin D intake (ug/d)c 14.9 (14.4, 15.4) 15.2 (14.5, 15.9) 14.6 (14.0, 15.3)
 Calcium intake (mg/d)c 1168 (1140, 1195) 1199 (1157, 1241) 1144 (1108, 1181)
  1. *P < 0.05, **P < 0.01, ***P < 0.001. Student’s t-test versus males
  2. a Subjects in the Tromsø study with valid food frequency questionnaires, serum 25(OH) D measurement, not been on a sunny vacation last 2 months, and not taking solarium regularly
  3. b As in the main cohort but with valid serum PTH measurement and with serum calcium < 2.51 mmol/L
  4. cIncluding supplements
  5. The data are mean (95% CI). The P values are not adjusted for multiple testing