Bone health in children and adolescents: risk factors for low bone density.

Osteoporosis is a common disease that is characterized by low bone mineral density (BMD). Decreased BMD is associated with increased fracture risk. In adults, normal BMD results from the balance between accrual of peak bone mass (PBM) at the end of adolescence, and subsequent bone loss with age. Although environmental factors play a role, hereditary factors are the major contributors (up to 80%) to the variability in PBM. This review examines the effects of genetics, physical activity and immobilization, smoking, chronic diseases and medications, vitamin D, calcium, and various other dietary factors on bone integrity in children, adolescents, and adults.