Interactive effects of habitual physical activity and calcium intake on bone density in boys and girls

Abstract

The purpose of this study was to assess the interactive effects of habitual physical activity (total and vigorous intensity) and calcium intake on bone mineral content (BMC) in prepubertal boys and girls. Seventy-six children, aged 8-11 yr, wore accelerometers for up to 7 days to assess activity. Calcium intake was estimated by a 4-day weighted food diary. BMC and areal density (bone mineral density) were measured at the total body, proximal femur, and femoral neck by using dual-energy X-ray absorptiometry. Moderated regression analyses were used to assess the contributions of physical activity (total and vigorous) and calcium intake to BMC, residualized for bone area and body mass. Interactive effects of vigorous activity (> or =6 metabolic equivalents) and calcium intake were found at the total body in boys (b = 2.90 x 10(-3)) and in girls (b = 6.58 x 10(-3)) and at the proximal femur (b = 9.87 x 10(-5)) and femoral neck (b = 2.29 x 10(-5); where b is the regression coefficient from final equation) in boys only; residualized BMC was high only if both vigorous activity and calcium intake were high. There were no interactive effects of total activity and calcium intake. This study provides evidence for synergistic action of habitual vigorous activity and calcium intake on bone mass in children. Recommendations for optimizing bone mass should reflect this synergism.

Subjective and objective measures of physical activity in relationship to bone mineral content during late childhood: the Iowa Bone Development Study

“…Additionally, we did not control for calcium intake, and others have shown an interactive effect of PA and calcium intake in children 23 24. With our accelerometry measures, the use of a 1 min epoch may have caused us to miss shorter activity bouts that may have had important associations with BMC 9.…”

Repeated Effects of Vigorous Interval Training in Basketball, Running-Biking, and Boxing on the Physical Self-Perceptions of Obese Adolescents

“…A validated Rowlands, Ingledew, Powell, & Eston, 2004) triaxial accelerometer (RT3, Stayhealthy Inc., Monrovia, CA) was used to assess the estimated intensity and energy expenditure of the participants' physical activity (Westerterp, 1999) from the start to the end of each 45-min exercise session. The accelerometer was carried by the belt on the right hip.…”

Bone Health: It’s More Than Calcium Intake

“…In this cross-sectional study of 38 girls and 38 boys between 8 and 11 years of age, there was a synergistic effect on bone density of a calcium intake of 700 to 800 mg/day and vigorous exercise (25-40 minutes per day). 10 Getting to the bottom line, I agree with Lanou et al that there is no direct evidence that calcium supplements at any level in childhood or adolescent have any impact on long-term bone health in adults, including osteoporosis. Even when using radiologic measures of bone health rather than calcium-balance studies, it is difficult to show a positive effect of calcium intake alone on bone mineral over the short term, let alone long-term benefits; however, I do agree with the National Academy of Sciences that the immediate goal of pediatric health care providers is still to achieve maximum peak bone mass in our adolescent patients.…”