calcium is soooooo ubiquitous on this earth's crust, foods etc., that very few if any should ever need to supplement it.
If anything what needs supp'd is magnesium, since usa people generally don't eat enough greens.
You all, I've brought up Sr frequently, but the discussion never takes flight. I hope you all will research it a bit, b/c its a far more important mineral of the alkaline-earth series than is Ca for most, and its powers amazing at tiny amounts over time.
Osteoporosis is not caused by low Ca in the diet by any stretch for 99% of the pop. , just like anemia don't get cured by ingesting more iron.