This paper was a retrospective analysis of data from 2710 men and 1143 women which included 626 postmenopausal women and overall, an average age of 30 or older in Seoul, South Korea. None of the study subjects were taking a calcium supplement and a 24 hour dietary recall was used to assess calcium intake.
Women with the highest calcium intake had lower total cholesterol levels and LDL cholesterol levels compared to those with the lowest calcium intake. With the coronary artery calcium scores (CACS) that were greater than 100 including different calcium intakes, dietary calcium intake was not significantly associated with CACS in either men or women. In addition, there were no negative effects of calcium on fasting glucose, insulin and platelet aggregation relative to all groups of dietary calcium intake. Higher phosphate levels did increase the risk for coronary artery calcification in men.
Commentary: There has been a longstanding advocacy for adequate dietary and/or supplemental calcium for the prevention and/or treatment of osteoporosis. There is also some evidence that calcium may be able to offer some vascular disease prevention by lowering cholesterol and blood pressure. Observational studies have even shown that women with higher calcium intake had a lower risk for death from cardiovascular disease and ischemic strokes (strokes due to lack of blood flow) when compared to women with lower calcium intake.
The lack of any detrimental effects of calcium on fasting glucose, insulin and platelet aggregation is reassuring as these are considered mechanisms by which calcium could have a negative impact on cardiovascular disease. Another mechanism by which dietary calcium intake might adversely affect cardiovascular disease is through vascular calcification.
The Women’s Health Initiative demonstrated that < 1000 mg calcium supplementation per day did not raise CACS. In the Auckland Calcium Study, calcifications of the aorta were decreased in the group with the highest dietary calcium intake.
However, there have been some recent studies that have demonstrated that there may be a positive relationship between higher blood levels of calcium and the increased risk for cardiovascular disease (myocardial infarction) and stroke, and others that show that calcium supplements might increase the risk of cardiovascular events while dietary calcium does not. Another observation is that the risk for cardiovascular events may be associated with the total of dietary and supplemental calcium intake. In a meta-analysis of 15 randomized blinded placebo-controlled trials, researchers evaluated 12,000 patients who were taking at least 500 mg of calcium supplementation per day (in addition to their dietary intake) and were older than 40. Calcium supplement intake was linked to a 30% increased risk for myocardial infarction. While this is considered only a modest increase, this would translate to about 36 more extra heart attacks over the course of two to five years in 12,000 women. In the midst of this controversy comes this retrospective study I have reported on today. It may be that we will have to rethink and reassess the role of calcium supplements in the prevention and treatment of osteoporosis and perhaps lower the recommendations from a total (diet and supplement) of 1200 mg/day to somewhere around 800 mg per day to find that sweet spot for bone and heart health without harm to either. Stay tuned for more news to come.
Hee Kim J, Won Yoon J, Won Kim K, et al. Increased dietary calcium intake is not associated with coronary artery calcification. Int. J Cardiology. 2012 Jun 14;157(3):429-31