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Self-Reported Calcium Intake and Bone Mineral Content in Children and Adolescents

College of Pharmacy and Nutrition (L.M.C., S.J.W., G.A.Z.), University of Saskatchewan, Saskatoon, CANADA
College of Kinesiology (D.T.D., R.A.F., D.A.B.), University of Saskatchewan, Saskatoon, CANADA
Department of Human Movement Studies, University of Queensland, Brisbane, AUSTRALIA (D.A.B.)

Address correspondence to: S.J. Whiting, Ph.D., College of Pharmacy and Nutrition, University of Saskatchewan, 110 Science Place, Saskatoon, SK, S7N 5C9, CANADA. E-mail: Susan.whiting{at}usask.ca.

Objective: We examined the relationship between self-reported calcium (Ca) intake and bone mineral content (BMC) in children and adolescents. We hypothesized that an expression of Ca adjusted for energy intake (EI), i.e., Ca density, would be a better predictor of BMC than unadjusted Ca because of underreporting of EI.

Methods: Data were obtained on dietary intakes (repeated 24-hour recalls) and BMC (by DEXA) in a cross-section of 227 children aged 8 to 17 years. Bivariate and multivariate analyses were used to examine the relationship between Ca, Ca density, and the dependent variables total body BMC and lumbar spine BMC. Covariates included were height, weight, bone area, maturity age, activity score and EI.

Results: Reported EI compared to estimated basal metabolic rate suggested underreporting of EI. Total body and lumbar spine BMC were significantly associated with EI, but not Ca or Ca density, in bivariate analyses. After controlling for size and maturity, multiple linear regression analysis revealed unadjusted Ca to be a predictor of BMC in males in the total body (p = 0.08) and lumbar spine (p = 0.01). Unadjusted Ca was not a predictor of BMC at either site in females. Ca density was not a better predictor of BMC at either site in males or females.

Conclusions: The relationship observed in male adolescents in this study between Ca intake and BMC is similar to that seen in clinical trials. Ca density did not enable us to see a relationship between Ca intake and BMC in females, which may reflect systematic reporting errors or that diet is not a limiting factor in this group of healthy adolescents.

Key words: dietary assessment, underreporting, calcium, bone mineral, dual-energy X-ray absorptiometry (DEXA), children, adolescents

Abbreviations: BA = bone area • BMC = bone mineral content • BMD = bone mineral density • BMR = basal metabolic rate • DEXA = dual energy X-ray absorptiometry • EI = energy intake • EI:BMR_est = ratio of energy intake to estimated BMR • PAQ-C = physical activity questionnaire for children • PHV = peak height velocity • PI = ponderal index (kg/m³)