Predictors of calcium retention in adolescent boys.
BACKGROUND
The relationship between calcium (Ca) intake and Ca retention in adolescent boys was recently reported.


OBJECTIVE
This study evaluated the influence of Ca intake, serum hormone levels, biomarkers of bone metabolism, habitual physical activity, habitual Ca intake, and physical fitness on Ca retention in the same sample.


METHODS
This study was a randomized, cross-over design that consisted of two 3-wk metabolic balance periods.


METHODS
The study took place on a university campus as a summer camp.


METHODS
A total of 31 American white boys (13-15 yr) participated in the study.


METHODS
Each subject consumed a controlled diet with one of five high-low Ca intake pairs that ranged from 670-2003 mg/d, which was manipulated utilizing a fortified beverage.


METHODS
Ca retention was determined by Ca intake minus urinary and fecal Ca excretion during each balance period.


RESULTS
Ca intake explained 21.7% of the variability in Ca retention, and serum IGF-I concentration explained an additional 11.5%. Other serum hormone levels did not significantly add to the model. Biomarkers of bone metabolism, habitual physical activity, habitual Ca intake, and physical fitness were not significant predictors of Ca retention in adolescent boys.


CONCLUSIONS
IGF-I, a regulator of growth during puberty, is an important predictor of Ca retention in adolescent boys. However, dietary Ca intake is an even greater predictor of Ca retention during this period of growth.
Purdue University, Foods and Nutrition, 700 W State Street, West Lafayette, Indiana 47907-2059, USA.
Kathleen M
KM
Hill
Michelle
M
Braun
Mark
M
Kern
Berdine R
BR
Martin
James W
JW
Navalta
Darlene A
DA
Sedlock
Linda
L
McCabe
George P
GP
McCabe
Munro
M
Peacock
Connie M
CM
Weaver
D000293:Adolescent; D000886:Anthropometry; D001628:Beverages; D015415:Biomarkers; D001842:Bone and Bones / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000652:urine; D002136:Calcium, Dietary / Q000378:metabolism*; D004032:Diet; D004311:Double-Blind Method; D005243:Feces / Q000737:chemistry; D005247:Feeding Behavior; D006184:Habits; D006728:Hormones / Q000097:blood; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008019:Life Style; D008297:Male; D009043:Motor Activity / Q000502:physiology; D010809:Physical Fitness; D011237:Predictive Value of Tests
D015415:Biomarkers; D002136:Calcium, Dietary; D006728:Hormones; D007334:Insulin-Like Growth Factor I; D002118:Calcium