Hucky, your suspicions are correct; this topic has been approached from different perspectives here. Do the search through all forums and skim through the topics.
I think its important to remember that supplements are are what they are a dietary supplement. When bones are so soft that an ADR or fusion is risky, other more complicated system conditions may be the cause. To Laura's point, our bodies metabolic processes are complex. E.g.:
There are a number of contributing factors for osteoporosis, including heredity, the amount of peak bone mass acquired during youth, and factors that contribute to an increased breakdown of bone and/or a decrease in the formation of new bone. Hyperthyroidism is associated with an increased excretion of calcium and phosphorous in the urine and stool, which results in a loss of bone mineral. This loss is documented by the measurement of bone density (densitometry) and leads to an increased risk of broken bones (fractures). If the hyperthyroidism is treated early, bone loss can be minimized. In the same manner, excessive amounts of thyroid hormone replacement medication can also result in bone loss.
http://www.medicinenet.com/script/ma...ticlekey=18637
There's also more info from this web site on osteoporosis here:
http://www.medicinenet.com/osteoporosis/focus.htm
But back to your question. Hopefully, your PCP will be looking closely at your blood lab results annually, so he/she should be able to monitor your overall health to manage your metabolic functions, right? As long as you do regular weight bearing exercise and eat healthy you'll maximize your chances of happy, long-term health!
Just my two cents.