Calcium is needed for your bones to be strong and to prevent osteoporosis. Elderly people who are at the highest risk for osteoporosis are strongly encouraged to take calcium supplements, but it may be too late for some. The damage could already be done.
The safest bet is to take calcium supplements and begin building strong bones when you're younger (if you can).
Also, high-impact exercise (especially running, walking, & jumping rope) are great physical activities, because they cause your bone density to increase, resulting in stronger bones.
And the newest results are in.........apparently almonds are very high in calcium! So eat lots of milk products (the most prevalent calcium provider), almonds, and get your DV of Vitamin D, which aids in the body's absorption of calcium.
Your bones will thank you!