A relatively recent research study found a significant association between calcium supplements and brain lesions in older adults:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4144340/

An excerpt from the article:

“This study indicates that the use of calcium-containing dietary supplements, even low dose supplements, by older adults may be associated with greater lesion volumes.”

Previous studies have shown that calcium supplements are also associated with greater risk of heart attack and heart related diseases.

I stopped taking any additional calcium supplements about five years ago, and now get all of my calcium from food sources.