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Demonstration of a difference in urinary calcium, not calcium absorption, in black and white adolescents
Author(s) -
Bell Norman H.,
Yergey Alfred L.,
Vieira Nancy E.,
Oexmann Mary Joan,
Shary Judith R.
Publication year - 1993
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650080912
Subject(s) - calcium , urinary calcium , endocrinology , medicine , femoral neck , urine , calcium metabolism , bone mineral , urinary system , isotopes of calcium , chemistry , osteoporosis
Abstract Bone mineral density (BMD) of the forearm, lumbar spine, and femoral neck is greater in black than in white children. Studies were performed to determine whether differences in intestinal absorption of calcium or urinary calcium or both account for an assumed more positive calcium balance and greater bone mass in black children. Normal black and white boys and girls were admitted to a metabolic ward and given a constant daily diet containing 1000 mg calcium, 60% as calcium carbonate, for 2½ days (study I) or 3½ days (study II). Fasting blood and 24 h urine collections were obtained, and in study II, unidirectional fractional absorption of calcium (α) was determined with stable isotopes of calcium. It was found that (1) serum 25‐hydroxyvitamin D (25‐OHD) and urinary calcium were lower and serum 1,25‐dihydroxyvitamin D [1,25‐(OH) 2 D] was higher in black than in white children, and (2) α was higher in boys than in girls with no racial difference, and (3) there were significant positive correlations between α and urinary calcium in the blacks and in the black and white children together. It is concluded that (1) α is higher in boys than in girls and (2) a lower urinary calcium, not increased intestinal absorption of calcium, is the means for a more positive calcium balance in blacks that accounts for the racial difference in BMD.