Osteopenia and osteoporosis
There are a variety of reasons for osteopenia, some hormonal and some related to the fact that calcium absorption lessens in elderly intestines.
Also, certain medications decrease the body’s ability to absorb calcium, including antacids. Soda with phosphates in it and smoking are also notorious bone health stealers.
Senior citizens need to be particularly conscious about the level of calcium in their diet and about which medications interfere with calcium absorption.
Women of white descent are most prone to osteoporosis.  If you are at risk it’s best not to wait until you’re fifty-something to start preventing osteoporosis.
Building stronger bones with a calcium-rich diet and weight-bearing exercise such as light weights in your twenties and thirties is more likely to prevent osteoporosis than preventive measures in your fifties.