RESEARCH Research and Professional Briefs Psychosocial Factors Influencing Calcium Intake and Bone Quality in Middle School Girls SHREELA V. SHARMA, PhD, RD, LD; DEANNA M. HOELSCHER, PhD, RD, LD; STEVEN H. KELDER, PhD, MPH; PAMELA DIAMOND, PhD; R. SUE DAY, PhD; ALBERT HERGENROEDER, MD ABSTRACT Calcium intake has been associated with promoting bone health in children and adolescents, thus preventing os- teoporosislaterinlife.Behaviorchangesuchasincreased calcium intake, as well as physiological factors such as bone quality, may be facilitated by psychosocial and en- vironmental factors. The purpose of this study was to identifypathwaysbywhichpsychosocialfactorsinfluence calcium intake and bone quality in middle school girls. The study design was cross-sectional. Baseline data from the Incorporating More Physical Activity and Calcium in Teens (IMPACT) study, collected in 2001-2003, were used. IMPACT was a 1.5-year nutrition and physical activity intervention study, designed to improve bone densityin717middleschoolgirlsinTexas.Mainoutcome measures were calcium intake determined using mean milligrams of calcium consumed per day and number of glasses of milk consumed per day, and bone quality de- termined using a calcaneal stiffness index. Confirmatory factoranalysisandpathanalysiswereperformedtoiden- tify the direct and indirect pathways used by various psychosocial factors such as knowledge, self-efficacy, out- come expectations, and milk availability at home, to in- fluence calcium intake and bone quality. Results showed that knowledge of osteoporosis and calcium-rich foods had an indirect effect on calcium intake, with outcome expectations as the mediating variable (=.035 and =.03, respectively; P0.05). Calcium self-efficacy had a significantindirecteffectoncalciumintake,withoutcome expectations as the mediator (=.085, P0.05). None of the variables significantly influenced bone quality. Thus, several direct and indirect pathways used to influence calcium intake among adolescent girls were identified. Thesefindingsarecriticalforthedevelopmentofeffective interventions to promote calcium intake in this popu- lation. J Am Diet Assoc. 2010;110:932-936. O steoporosis is a disease characterized by low bone mass and deterioration of bone tissue, leading to increased risk of bone fractures (1). Dietary factors such as calcium and vitamin D intake during childhood aremajordeterminantsofosteoporosislaterinlife(2).Up to 90% of peak bone mass is acquired by age 18 years in girls and age 20 years in boys, which makes childhood a critical time to promote behaviors that improve bone health(3).Thesebehaviorsincludeconsumingtherecom- mended amount of calcium and vitamin D, engaging in regularphysicalactivity,andavoidingsmokingandalco- hol (2-5). These modifiable behaviors are influenced by psychosocialandenvironmentalfactorsthat,inturn,me- diatetheassociationsbetweenbehavioranddisease(6-9). Although there is some literature examining the psycho- social correlates of calcium intake (10), one of the stron- gest determinants of bone mass, none have examined these interrelationships with respect to bone quality in adolescent girls. Since women are at a higher risk for osteoporosis (11), it can be advantageous to examine these relationships in a sex-specific manner. Thepurposeofthisstudywastoidentifythepathways bywhichpsychosocialfactorssuchasknowledgeofosteo- porosis and calcium-rich foods, self-efficacy toward con- suming calcium-rich foods, calcium outcome expecta- tions, and milk availability influence calcium intake and bonequalityusingpathanalysisinacohortofadolescent females. The hypothesis was that these psychosocial fac- tors interact and use various direct and indirect path- ways to influence calcium intake and bone quality. METHODS This study was secondary data analysis using baseline data from The Incorporating More Physical Activity and S. V. Sharma is an assistant professor of epidemiology, P. Diamond is an assistant professor of health promo- tion behavioral sciences, and R. S. Day is an associate professor of epidemiology and nutrition, Michael and Susan Dell Center for the Advancement of Healthy Liv- ing, School of Public Health, The University of Texas Health Science Center at Houston. D. M. Hoelscher is a professor of biological sciences and nutrition, and S. H. Kelder is a professor of epidemiology, Michael and Su- san Dell Center for the Advancement of Healthy Living, School of Public Health, The University of Texas Health Science Center, Austin Regional Campus, Austin. A. Hergenroeder is a professor of pediatrics, Baylor College of Medicine, and chief, Adolescent Medicine Service and Sports Medicine Clinic, Texas Children’s Hospital, Houston. Address correspondence to: Shreela V. Sharma, PhD, RD, LD, Michael and Susan Dell Center for the Ad- vancement of Healthy Living, School of Public Health, The University of Texas Health Science Center at Hous- ton, 1200 Herman Pressler, E RAS 603, Houston, TX 77030. E-mail: Shreela.V.Sharma@uth.tmc.edu Manuscript accepted: September 30, 2009. Copyright © 2010 by the American Dietetic Association. 0002-8223/$36.00 doi:10.1016/j.jada.2010.03.013 932 Journal of the AMERICAN DIETETIC ASSOCIATION © 2010 by the American Dietetic Association