Calcium supplements, often prescribed to prevent and treat osteoporosis, could double the risk of having a heart attack, according to a new study published in the journal Heart. The study tracked nearly 24,000 men and women for an average of 11 years. Calcium from foods and diet are generally considered safer than supplements, because the risk of heart problems from excessive doses generally outweighs the benefits – including prevention of bone fractures. Calcium from food also triggers effects on metabolism and levels in the bloodstream, which daily calcium supplements cannot reproduce.