Abstract
There is strong evidence that osteoporosis is not a single disease with a single cause but, rather, the cumulative response of bone over time to a variety of noxious factors. Inadequate dietary calcium consumption is such a factor, but there are many others--some of which affect bone by affecting calcium homeostasis, and others of which affect bone directly. These include excessive dietary phosphate and acid consumption, inadequate sunlight or vitamin D consumption, use of bone toxins such as tobacco and alcohol, use of drugs that affect calcium homeostasis such as glucocorticoids and barbiturates, and insufficient physical activity or weight bearing. To these environmental factors can be added the adverse effects on bone of the numerous physiologic stresses and diseases that each person may encounter in the course of a lifetime--pregnancy, lactation, febrile illnesses, and transient periods of immobilization as well as diseases that cause bone loss directly. The success of those factors depends on the competency of regulatory mechanisms.