title: Calcium retention in relation to calcium intake and postmenarcheal age in adolescent females.
abstract: Achievement of maximal calcium retention during adolescence may influence the magnitude of peak bone mass and subsequently lower the risk of osteoporosis. Calcium retention is generally considered to reach a plateau at a certain calcium intake. To test this hypothesis, calcium balance was measured in 35 females with a mean (+/-SD) age of 12.7 +/- 1.2 y (range: 12-15 y) who consumed from 841 +/- 153 to 2173 +/- 149 mg Ca/d. Subjects ate a basal diet that included a fortified beverage containing different amounts of calcium citrate malate. Twenty-one subjects were studied at two dietary calcium intakes with use of a crossover design. Results from a previous study in 14 subjects who were studied at only one calcium intake were included in the data analysis. Calcium retention was modeled as a nonlinear function of calcium intake that included a parameter representing mean maximal retention. Mean maximal calcium retention was 473 mg/d (95% CI: 245, 701 mg Ca/d). At higher postmenarcheal ages, maximal calcium retention was lower but the intake required to achieve this was not affected. Calcium intake explained 79% and 6%, respectively, of the variation in fecal and urinary calcium excretion. Intake of 1200 mg Ca/d, the recommended dietary allowance for calcium published in 1989, resulted in a mean calcium retention that was 57% of the maximal value (95% CI: 25%, 89%). Intake of 1300 mg Ca/d was the smallest intake that allowed some adolescent females to achieve 100% of maximal calcium retention (95% CI: 26%, 100%). These data support the idea that calcium retention plateaus at a certain calcium intake although it continues to increase at intakes > 2 g/d.
authors.affiliation: Department of Foods and Nutrition, Purdue University, West Lafayette, IN 47907-1264, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Jackman
authors.forename: S S
authors.initials: SS
authors.lastname: Millane
authors.forename: B R
authors.initials: BR
authors.lastname: Martin
authors.forename: O B
authors.initials: OB
authors.lastname: Wood
authors.forename: G P
authors.initials: GP
authors.lastname: McCabe
authors.forename: M
authors.initials: M
authors.lastname: Peacock
authors.forename: C M
authors.initials: CM
authors.lastname: Weaver
mesh_terms: D000293:Adolescent; D002118:Calcium / Q000008:administration & dosage / Q000378:metabolism* / Q000652:urine; D002648:Child; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D008572:Menarche
chemical_list: D002118:Calcium