I’m certainly no expert, but i am fundamentally sceptical of most supplements. First of all, they are not regulated by the FDA; not that FDA approval makes drugs safe! Secondly, it is very difficult to know what amount of a supplement we need and overdosing can be very dangerous. Thirdly, we need to get our vitamins and minerals from food as they are much easier to absorb.

Regarding calcium, some studies have shown that taking calcium supplements is linked to kidney stones and cardiovascular disease.
The connection between calcium and cardiovascular disease is plausible. Calcium deposits are part of artery-clogging plaque. They also contribute to stiffening of the arteries and can interfere w the functioning of heart valves.

Given the uncertainty about the balance of benefits and risks of calcium supplements, it's probably best to get the calcium you need from dietary sources.