M. Braun*1, B. R. Martin1, M. Kern*2, G. P. McCabe*3, M. Peacock4, A. Machtan*1, J. Liesmann*1, A. Kempa-Steczko*1, C. M. Weaver1. 1Foods & Nutrition, Purdue University, West Lafayette, IN, USA, 2San Diego State University, San Diego, CA, USA, 3Statistics, Purdue University, West Lafayette, IN, USA, 4Indiana University School of Medicine, Indianapolis, IN, USA.
We previously determined the relationship between calcium (Ca) intake and Ca retention in adolescent girls. The intake where maximal Ca retention occurred was determined by a non-linear regression model. It is not known whether the larger skeletal mass of boys requires more dietary Ca to optimize Ca retention or if boys utilize Ca more efficiently than girls.
Forty-four adolescent males, aged 13-15 were tested on two Ca intakes each that ranged from 800-2100 mg/day in a random order, crossover design. All procedures were approved by the Purdue University and Indiana University School of Medicine Institutional Review Boards. Two 3-week metabolic balance sessions were separated by a 2-week wash-out period. Subjects consumed a controlled diet and Ca intake was varied via fortified beverage. After one week equilibration period, calcium retention was determined as intake minus excreta over the next two weeks.
Compared to girls studied during their period of pubertal growth, boys had higher Ca retention at all intakes. This higher Ca retention was achieved through lower urinary output and higher Ca absorption. Thus, boys attain a higher bone mineral content by increased utilization efficiency. Adding measures of body size into the model did not eliminate gender differences.
Disclosures: M. Braun, None.