Dear Dr. Mirkin: Should I take calcium pills?
Taking calcium pills both with and without vitamin D is associated with a 15 percent increased risk for heart attacks and strokes (British Journal of Medicine. April 19, 2011; American Heart Journal, 2008;156:556-63). Taking one gram of calcium daily for five years markedly increase heart attacks and strokes (BMJ, January 15, 2008). Treating 1000 people with calcium or calcium and vitamin D for five years would cause an additional six heart attacks or strokes and prevent only three fractures.
Calcium in pills, unlike calcium in foods, causes a rise in blood calcium levels that can damage arteries by:
- increasing clot formation, a major cause of heart attacks and strokes (J Bone Miner Res. 1997;12:1959-70),
- thickening neck artery plaques (Atherosclerosis. 2007;194:426-32), and
- calcifying main arteries (J Bone Miner Res. 2010;25:505-12).
A review of 11 controlled studies involving about 12,000 patients found that taking calcium pills (at least 500 mg/day) without also taking vitamin D is associated with almost a 30 percent increase in heart attack risk (British Medical Journal, July 29, 2010). Furthermore, most people take calcium supplements to help prevent or treat osteoporosis. Taking calcium pills without vitamin D pills has not been shown to reduce bone fractures.
I believe that you should get your calcium in food, not pills. If you feel that you need to take calcium pills, take 1000 mg of calcium with 1000 IU of vitamin D. Excess calcium in the blood blocks the conversion of inactive vitamin D to active vitamin D. Lack of active vitamin D, by itself, can increase risk for heart attacks.