Dietary calcium does not help older people avoid fractures, and might in fact cause other problems -- even cancer. One less thing to worry about!

Wow, this is news to me. Exercise matters more than diet for strengthening bones:

Despite the findings that supplements might fuel the growth of cancer, Americans love their supplements. A survey done in 2012 found 75 percent of Americans who take supplements would take them, even if they are proven not to benefit health. Americans spend $12 billion a year on supplements. 

What can people do? 

Exercise is one possibility. Weight-bearing exercise such as walking, running, playing tennis, lifting weights and dancing can strengthen bones. Swimming and bicycling does less to build strong bones, according to the NIH. 

Cutting down on alcohol and stopping smoking can also help — both can weaken bones.