The recommended dietary allowance for calcium for the female adolescent is an extrapolated figure. Very little information exists on normal calcium metabolism in this age group. Meeting calcium requirements for maximal bone growth may be the most crucial in this age group to lower the risk of developing osteoporosis in later years. The proposed study will use dual isotopic tracer techniques combined with a three week metabolic study in 10 adolescent girls aged 12-14 and 10 young women aged 20-30. Major hypotheses to be tested include: 1) Skeletal requirements of adolescent girls are greater than in adult women as reflected by a) increased bone accretion, b) greater calcium retention, and c) reduced calcium urinary losses. 2) Calcium fractional absorption and endogenous fecal losses are not greater in adolescent girls than in adults. 3) Bone calcium turnover is grater in adolescent than adult females. Stable isotopes of calcium will be administered orally and by intravenous injection after a one week equilibrium period on a controlled diet contain- ing 1200 mg Ca/day. Total calcium will be analyzed by atomic absorption mass spectrometry and stable isotopes will be analyzed by high resolution fast atom bombardment mass spectroscopy. Analysis of complete urine and fecal collections and periodic blood samples will provide data for multi- compartmental and stochastic analysis of calcium metabolism. Correlations with hormone levels and biochemical markers of bone turnover will also be made.
| Hill, Kathleen M; Braun, Michelle M; Egan, Kara A et al. (2011) Obesity augments calcium-induced increases in skeletal calcium retention in adolescents. J Clin Endocrinol Metab 96:2171-7 |
| Hill, Kathleen M; McCabe, George P; McCabe, Linda D et al. (2010) An inflection point of serum 25-hydroxyvitamin D for maximal suppression of parathyroid hormone is not evident from multi-site pooled data in children and adolescents. J Nutr 140:1983-8 |
| Wu, Lu; Martin, Berdine R; Braun, Michelle M et al. (2010) Calcium requirements and metabolism in Chinese-American boys and girls. J Bone Miner Res 25:1842-9 |
| Weaver, Connie M; McCabe, Linda D; McCabe, George P et al. (2008) Vitamin D status and calcium metabolism in adolescent black and white girls on a range of controlled calcium intakes. J Clin Endocrinol Metab 93:3907-14 |
| Hill, Kathleen M; Braun, Michelle; Kern, Mark et al. (2008) Predictors of calcium retention in adolescent boys. J Clin Endocrinol Metab 93:4743-8 |
| Walker, Marcella D; Novotny, Rachel; Bilezikian, John P et al. (2008) Race and diet interactions in the acquisition, maintenance, and loss of bone. J Nutr 138:1256S-60S |
| Braun, Michelle; Palacios, Cristina; Wigertz, Karin et al. (2007) Racial differences in skeletal calcium retention in adolescent girls with varied controlled calcium intakes. Am J Clin Nutr 85:1657-63 |
| Braun, Michelle; Martin, Berdine R; Kern, Mark et al. (2006) Calcium retention in adolescent boys on a range of controlled calcium intakes. Am J Clin Nutr 84:414-8 |
| Weaver, Connie M; Rothwell, Arlene P; Wood, Karl V (2006) Measuring calcium absorption and utilization in humans. Curr Opin Clin Nutr Metab Care 9:568-74 |
| Wastney, Meryl E; Martin, Berdine R; Bryant, Rebecca J et al. (2003) Calcium utilization in young women: new insights from modeling. Adv Exp Med Biol 537:193-205 |
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