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Calcium retention and hormone levels in black and white women on high‐ and low‐calcium diets
Author(s) -
DawsonHughes Bess,
Harris Susan,
Kramich Carolyn,
Dallal Gerard,
Rasmussen Helen M.
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.5650080702
Subject(s) - calcium , endocrinology , parathyroid hormone , medicine , calcium metabolism , urine , chemistry
Black‐white differences in calcium metabolism are sought because they may reveal why blacks have higher bone mass than whites. Comparative studies of calcium absorption in blacks and whites are not available. In this study, we compare fractional calcium retention, an index of calcium absorption, and calcium regulating hormone levels in black and white women on a high‐calcium diet and after adaptation to a low‐calcium diet. A total of 30 healthy women (15 black and 15 white) had measurements of fractional 47 Ca retention and calcium regulating hormone levels after 8 weeks on a 2000 mg calcium diet and, subsequently, after 1, 2, 4, and 8 weeks on a 300 mg calcium diet. By 2 weeks after the diet change, fractional 47 Ca retention, parathyroid hormone (PTH), and 1,25‐dihydroxyvitamin D [1,25‐(OH) 2 D] had reached a plateau at higher levels, urine calcium at a low level, and serum calcium at the same level (repeated‐measures ANOVA). Fractional 47 Ca retention, serum calcium, and PTH were similar on both diets in blacks and whites. Blacks had higher levels of 1,25‐(OH) 2 D on both diets (e.g., 125.1 ± 53.5 SD versus 73.4 ± 19.0 pmol/liter, P = 0.003 on low‐calcium diet) and a greater increase in 1,25‐(OH) 2 D after the diet change (33.9 ± 30.1 SD versus 11.8 ± 17.9 pmol/liter, P = 0.021). Serum phosphorus was lower in blacks throughout. For hormone levels and fractional calcium retention to stabilize after a diet change, 2 weeks was needed. Similar levels of fractional retention in black and white women despite higher levels of 1,25‐(OH) 2 D in blacks suggest that blacks may have a gut resistance to the action of 1,25‐(OH) 2 D.