I read some article online a while back saying that supplementing with vitamin d3 could cause calcification of heart valves/ arteries? is it safe?

Very safe but...: Vitamin d3 is very safe ; of tremendous benefit for preventing many illnesses. It helps our bodies to absorb calcium. I advise everyone to take d in the fall ; winter months. But it's also wise to take vitamin k (or eat foods rich in vit k) as that helps assure the calcium goes into our bones ; doesnnot wind up in our arteries or heart valves. See http://bit.Ly/1ekkvkv ; http://bit.Ly/18qtb7y.