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Bone calcium turnover during pregnancy and lactation in women with low calcium diets is associated with calcium intake and circulating insulin-like growth factor 1 concentrations

Author:
O'Brien, Kimberly O, Donangelo, Carmen M, Zapata, Carmina L Vargas, Abrams, Steven A, Spencer, E Martin, King, Janet C
Source:
American journal of clinical nutrition 2006 v.83 no.2 pp. 317
ISSN:
0002-9165
Subject:
maternal nutrition, pregnant women, lactating women, pregnancy, diet, dietary minerals, calcium, nutrient intake, mineral metabolism, stable isotopes, bone mineralization, bone density, bone resorption, insulin-like growth factor I, nutrient balance, nutrient deficiencies
Abstract:
BACKGROUND: Few data exist on longitudinal changes in bone calcium turnover rates across pregnancy and lactation. OBJECTIVE: Our aim was to characterize calcium kinetic variables and predictors of these changes across pregnancy and early lactation in women with low calcium intakes. DESIGN: Stable calcium isotopes were administered to 10 Brazilian women during early pregnancy (EP; weeks 10-12 of gestation), late pregnancy (LP; weeks 34-36 of gestation), and early lactation (EL; 7-8 wk postpartum). Multicompartmental modeling was used to assess the rates of bone calcium turnover in relation to calcium intakes and circulating concentrations of parathyroid hormone (PTH), insulin-like growth factor 1, and 1,25-dihydroxyvitamin D. RESULTS: Rates of bone calcium deposition increased significantly from EP to LP (P = 0.001) and were significantly associated with serum PTH during LP (P </= 0.01). Rates of bone calcium resorption were also higher during LP and EL than during EP (P </= 0.01) and were associated with both PTH (P </= 0.01) and IGF-1 (P </= 0.05) during LP but not during EL. Net balance in bone calcium turnover was positively associated with dietary calcium during EP (P </= 0.01), LP (P </= 0.01), and EL (P </= 0.01). The mean (±SD) calcium intake was 463 ± 182 mg/d and, in combination with insulin-like growth factor 1, explained 68-94% of the variability in net bone calcium balance during pregnancy and lactation. CONCLUSIONS: Net deficits in bone calcium balance occurred during pregnancy and lactation. Increased dietary calcium intake was associated with improved calcium balance; therefore, greater calcium intakes may minimize bone loss across pregnancy and lactation in women with habitual intakes of <500 mg calcium/d.
Agid:
2070
Handle:
10113/2070