Calcium Intake and Risk of Myocardial Infarction

By:  Lila Ahmed, PharmD Candidate c/o 2013

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In the past, numerous research efforts have attempted to prove the benefits and risks of calcium and multivitamin supplements with little success. Most of the studies performed were inconclusive and did not provide us with significant data; while some studies have found that calcium is beneficial for high blood pressure and heart diseases, others did not.¹ However, a recent correlation between calcium intake and the risk of myocardial infarction and stroke presents an interesting topic worth further exploration.

This European study published in Heart in May 2012 was led by epidemiologist Sabine Rohrmann at the University of Zurich. It involved 24,000 participants in a German arm of the European Prospective Investigation into Cancer and Nutrition (EPIC). All participants were between the ages of 35 and 64 when they enrolled in the study between 1994 and 1998.² Normal diets were assessed for the preceding 12 months and participants were quizzed about regular vitamin and mineral supplementation. Patients that had a previous myocardial infarction (MI), stroke, or transient ischemic attack (TIA) were excluded from the study. The large cohort of men and women was followed for 11 years.²

This study showed that patients who took calcium supplements, either as calcium or as part of a multivitamin, had an 86 % higher risk of MI than those who used no supplements at all.1 The researchers found no link between total dietary calcium and stroke or heart disease deaths. However, they did find that a higher intake of dietary calcium reduced the risk of heart attack. For example, one of the groups with the higher intake of dietary calcium showed a 31% lower risk of heart attack than those who had the least calcium in their diet.²

The mechanism by which calcium supplementation increases the risk of heart attacks is unknown. However, calcium supplements cause an acute spike in serum calcium levels, which dietary calcium from foods does not.² It is hypothesized that too much calcium in the blood can cause vascular calcification which may be adversely affecting blood coagulability.³

Calcium supplements have always been accepted by the public and even by physicians as the safe and natural way to prevent osteoporosis especially in elderly women. These findings challenge that viewpoint. More physicians now encourage eating your calcium from foods, instead of utilizing supplementations. The Institute of Medicine suggests that women ages 19-50 and men ages 19-70 should get 1,000 milligrams of calcium daily, whereas women ages 51 and older and men over 70 should get 1,200 milligrams of calcium daily.³ Most people typically have a baseline calcium level of about 300 milligrams without any supplementation. A cup of milk or yogurt contains about 300 milligrams of calcium.³ Therefore, to determine the amount of supplementation necessary (if any), one can subtract the total amount of calcium from your diet from your total recommended daily allowance based on your age and gender. Each patient’s calcium intake should be individualized based on his or her diet. Increase in dietary intake of calcium should always be recommended before supplementation, although supplements can be recommended to make up the dietary shortfall.

This study was not conducted to abandon all supplements in general, but rather to be aware of how much calcium a person is taking in.. This is a huge opportunity for pharmacists to counsel their patients not only on calcium supplementation, but supplements in general. Many older patients take calcium supplements and a multivitamin.in addition to dietary calcium. Without the help of a pharmacist, they could be overdosing unknowingly. Thus, assessing their dietary intake before recommending a supplement is important. Pharmacists can also let patients know that for those who wish to avoid dairy foods, there are other options rich with calcium. These include collards greens, beans, broccoli, cabbage, figs, almonds and fortified foods like cereal, certain fruit juices, and breakfast bars.³ Lastly, pharmacists should inform their patients on how to split the calcium supplement dose in order to minimize spikes in serum levels, as these spikes are likely to be a cause of the increase heart attack rates.

In conclusion, this new study has finally shed some light on the question of calcium and cardiovascular risks. Both pharmacists and physicians should be more cautious in recommending calcium supplementation to their patients. Time should be taken to make sure patients are not unnecessary consuming supplements, and patients should be counseled on the benefits of dietary calcium.

SOURCES:

1. Doheny, Kathleen. Calcium Supplements May Raise Heart Attack Risk. WebMD. May 2012. http://www.webmd.com/heart/news/20120523/calcium-supplements-may-raise-heart-attack-risk. Accessed November 16, 2012.
2. Li K, Kaaks R, Linseisen J et al. Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg). Heart 2012;98:920-925.
3. Calcium and Cardiovascular Risk. Pharmacist’s Letter. July 2012. http://pharmacistsletter.therapeuticresearch.com/pl/ArticleDD.aspx?cs=STUDENT&s=PL&pt=2&fpt=31&dd=260901&pb=PL&searchid=38348980&segment=2606. Accessed November 16, 2012.