Percent true calcium absorption, mineral metabolism, and bone mineralization in children with cystic fibrosis: effect of supplementation with vitamin D and calcium.
OBJECTIVE
To assess whether percent true calcium absorption (alpha) is normal in children with cystic fibrosis (CF) and to assess whether supplementation with 2,000 IU vitamin D(3), 1 g calcium, or both will alter alpha, mineral metabolism, and/or bone mass in children with CF.


METHODS
Fifteen children ages 7-13 were randomly assigned to one of four different orders to receive all four 6-month treatments including placebos. Change in 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D (1,25(OH)(2)D), PTH, bone turnover markers, and minerals after 6 months, and bone mineral content (Hologic 1000W) after 9 months was measured. alpha was measured by a dual stable isotope method using (48)Ca intravenously and (46)Ca orally and measuring (48)Ca, (46)Ca, and (42)Ca in a 24-hr urine using High Resolution Inductively Coupled Mass Spectroscopy (HR-ICP-MS). Analysis used Wilcoxon Sign Ranks.


RESULTS
alpha was in the normal range and did not differ by treatment (P 35 +/- 10%, Ca 38 +/- 23%, D 36 +/- 11%, D + Ca 46 +/- 21%). One gram calcium did not increase serum or urine calcium. Two thousand IU D(3) did not increase 25-OHD or change 1,25(OH)(2)D. Serum and urine minerals, markers of bone turnover and bone mineral gains did not differ by treatment.


CONCLUSIONS
alpha is normal in children with CF. One gram calcium and/or 2,000 IU D(3) does not change alpha or increase 25-OHD, serum calcium, or mineralization. Longer trials of a significantly higher dose of vitamin D(3) shown to increase serum 25-OHD are needed to assess effects on mineral metabolism and bone mass accrual. However, study of therapeutic options other than calcium and vitamin D should be encouraged.
Hillman
Laura S
LS
Department of Child Health, University of Missouri, Columbia, Missouri 65212, USA. hillmanl@health.missouri.edu
Cassidy
James T
JT
Popescu
Mihaela F
MF
Hewett
John E
JE
Kyger
Joseph
J
Robertson
J David
JD
D000293:Adolescent; D015519:Bone Density / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D002113:Calcification, Physiologic / Q000187:drug effects; D002118:Calcium / Q000008:administration & dosage* / Q000493:pharmacokinetics; D002648:Child; D003550:Cystic Fibrosis / Q000150:complications / Q000378:metabolism*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D014807:Vitamin D / Q000008:administration & dosage* / Q000493:pharmacokinetics
D050071:Bone Density Conservation Agents; D014807:Vitamin D; D002118:Calcium