Familial and environmental influences on bone growth from 11-17 years.

The influences on bone growth of familial factors, nutrition and physical activity are described in a cohort of 108 children (56M, 52F). Distal forearm bone width, mineral content and volumetric density, anthropometry, pubertal status, nutritional intake and physical activity were measured at ages 11, 13, 15 and 17 y. Parental forearm bone status was also determined. Both mothers' and fathers' bone variables were significant predictors of the respective children's bone variables, but heritability estimates were greater between mothers and their children than between fathers and their children. By age 17 y boys had attained 101%, 85% and 89% of their fathers' height, bone mineral content and volumetric density, respectively; girls had attained 103%, 95% and 98% of their mothers' height, bone mineral content and volumetric density, respectively. There were no consistent associations among nutrient variables and bone status or rate of change in bone status. However, there was a significantly greater increase in bone mineral content and density from 11-17 y in those girls with consistently high calcium intake. There were no significant correlations between physical activity and bone values or rate of change of bone values. Age, gender, pubertal status, height, weight and parental bone values accounted for 80%, 71% and 49% of the variance of bone mineral content, bone width and volumetric density, respectively and 52%, 55% and 58% respectively of the variance of change in these variables. After age, gender, sexual maturity and body size, heritability accounts for the greatest variance in bone values through adolescence.