Does the calcium content of the bones in women decreases after 30? if yes,then why and what can be done to prevent this from happening? age-20

Bone content: By age 20 you have almost reached your optimal bone mass and may get a bit more over the next few years. If you are healthy woman and do not develop any troubling disease by age 50 your bone mass should be what it was at age 25. Then menopause comes and bone loss starts but that can be prevented when you see your doctor soon after menopause.