How to build bone? The best answer is to get outside and do weight bearing exercise over the course of your life. Walking and weight training are good for your skeleton.
The bone is a living organ. We make it and we dissolve it over and over again. We can modify the process of bone loss which goes along with aging. If we can interfere with the back side of the process, resorbing it, then theoretically we can build up bone.
To go back to the bone bank analogy, think of the difference between a checking account and a certificate of deposit. With a certificate of deposit, you put the money in but it’s more difficult to take it out. That’s what happens with medications like Fosamax and Boniva.
We make the bone difficult to resorb and therefore make withdrawals from the bone bank more difficult. This works to some extent but only for about 2 years. The problem is the bone that is built up is not properly repaired and then you can end up with a new kind of fracture.
There are other ways of messing with your physiology but many of them have significant side effects as well. For instance, we take from the world of cancer treatment medications and apply them in lesser doses for osteoporosis. Virtually all of cancer treatment severely decimates the skeleton and so most cancer regimens use very powerful bone building chemicals to undo the damage of the poison. Unfortunately, chemotherapy is extremely destructive to healthy tissue as well as cancer including the skeleton.