s Description): Optimal calcium retention is a prerequisite for building maximal peak bone mass within the genetic potential, a key to reducing risk of osteoporosis later in life. The investigators have determined that maximal calcium retention averages 423 mg/day during the period of rapid skeletal accretion in white adolescent girls at a mean dietary calcium intake of 1300 mg/day. Urinary calcium explains more than 50% of the variance in calcium retention. However, urinary sodium (i.e. sodium intake) is a major determinant of urinary calcium excretion, and the effect of sodium intake on maximal calcium retention is not known. Nor is its effect known in black adolescents who have higher bone density and lower calcium excretion than white adolescents. The primary aim of this proposal is to test the hypothesis that high dietary sodium increases the calcium intakes required for optimal calcium retention in both black and white adolescent girls. Calcium retention will be measured at two levels of dietary sodium in a randomized crossover design on one of two levels of dietary calcium intake in black and white adolescent girls during three week metabolic periods. The investigators hypothesize that the mechanisms which regulate sodium reabsorption in the renal tubules also regulate calcium retention. Increased incidence of hypertension in blacks compared to whites has been attributed to increased sodium retention. Sodium intake induced changes in calcium and sodium retention in both races will be related to changes in sodium handling (plasma renin activity, serum aldosterone, and salt sensitivity) and calcium-regulating hormones, biomarkers of bone turnover, and bone mass. These studies are expected to define optimal calcium and sodium intakes for optimizing peak bone mass in both white and black adolescents. Furthermore, they should provide an explanation for the paradox that blacks can build higher bone density, have a lower rate of bone turnover, and excrete less urinary calcium on the same sodium loads compared to whites.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD036609-02
Application #
2889529
Study Section
Special Emphasis Panel (ZHD1-RRG-K (06))
Program Officer
Mcgowan, Joan A
Project Start
1998-07-01
Project End
2002-06-30
Budget Start
1999-07-01
Budget End
2000-06-30
Support Year
2
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Purdue University
Department
Nutrition
Type
Other Domestic Higher Education
DUNS #
072051394
City
West Lafayette
State
IN
Country
United States
Zip Code
47907
Palacios, Cristina; Wigertz, Karin; Braun, Michelle et al. (2013) Magnesium retention from metabolic-balance studies in female adolescents: impact of race, dietary salt, and calcium. Am J Clin Nutr 97:1014-9
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
Palacios, Cristina; Wigertz, Karin; Martin, Berdine R et al. (2010) Racial differences in potassium homeostasis in response to differences in dietary sodium in girls. Am J Clin Nutr 91:597-603
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
Thierry-Palmer, Myrtle; Henderson, Veronica M; Hammali, Rafiq El et al. (2008) Black and white female adolescents lose vitamin D metabolites into urine. Am J Med Sci 335:278-83
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
Wigertz, Karin; Palacios, Cristina; Jackman, Lisa A et al. (2005) Racial differences in calcium retention in response to dietary salt in adolescent girls. Am J Clin Nutr 81:845-50
Palacios, Cristina; Wigertz, Karin; Martin, Berdine R et al. (2004) Sodium retention in black and white female adolescents in response to salt intake. J Clin Endocrinol Metab 89:1858-63
Weaver, Connie M; Liebman, Michael (2002) Biomarkers of bone health appropriate for evaluating functional foods designed to reduce risk of osteoporosis. Br J Nutr 88 Suppl 2:S225-32