Pathways used by psychosocial and environmental factors to influence calcium intake and bone health in middle-school girls

Objectives: The purpose of the study was to identify the pathways used by various psychosocial and environmental factors to influence calcium intake and bone health in middle-school girls in Texas. Methods: Data from the Incorporating More Physical Activity and Calcium in Teens (IMPACT) study collected in 2001-2003 were utilized for the analysis. IMPACT was a 1 1/2 year nutrition and physical activity intervention study designed to improve bone density in 718 middle-school girls. The psychosocial and environmental variables included knowledge of calcium-rich foods and osteoporosis, self-efficacy and outcome expectations towards consuming calcium-rich foods and milk availability at home. Calcium intake was defined as the milligrams of calcium consumed per day and the number of glasses of milk consumed per day. Bone health was measured using quantitative ultrasound of the calcaneus to determine the calcaneal stiffness index. Data was analyzed using a Structural Equations Modeling approach to identify direct and indirect pathways used by psychosocial and environmental factors to influence calcium intake and bone health. Results: The final path model showed that outcome expectations and milk availability at home directly influence calcium intake (ß=0.25, p<0.05 and ß=0.28, p<0.05 respectively). Knowledge of calcium-rich foods and osteoporosis indirectly influence calcium intake with outcome expectations as the mediating variable (ß=0.035, p<0.05 & ß=0.03, p<0.05 respectively). Calcium self-efficacy also indirectly influences calcium intake with outcome expectations as the mediating variable (ß=0.09, p<0.05). No direct or indirect pathways were identified for bone health. Conclusion: The present study identified several direct and indirect pathways used by various psychosocial factors in influencing calcium intake among adolescent girls. These results are especially critical when trying to design effective interventions for promoting calcium intake in this population.