Calcium Increases Risk of Heart Attacks

Published: October 23, 2012

As we've noted for decades, we do not recommend taking calcium supplements unless you have loss of bone density (osteoporosis). This study showed that women in their 70s who took calcium supplements had a 50% increased risk of heart attacks. I suspect this risk can be avoided by taking other nutrients to balance the calcium—especially magnesium and vitamin K.

In this placebo-controlled trial in an academic medical center in urban New Zealand, 1,471 postmenopausal women (mean age 74 years) were enrolled. 732 were given 1,000 mg of calcium citrate a day and 739 received placebo. Women were included if they had been postmenopausal for more than 5 years, were 55 years or older and had a life expectancy of more than 5 years. Those taking the calcium had a 49% increased risk of heart attack.

Research shows more and more that when you give a single nutrient without balancing it with others it creates problems. With calcium, the key balancing nutrients are:

  1. Magnesium—Low magnesium, which is present in most Americans who do not supplement, is strongly associated with an increased risk of heart attacks. Magnesium and calcium are balanced in the body, and raising one can lower the other. What works best is to optimize and balance both.
  2. Vitamin K—Vitamin K is also needed (along with magnesium and vitamin D) to build strong bones. Vitamin K (as K2) has been shown to decrease the risk of heart disease. For the "science-minded" reader, the information below "Vitamin K and Heart Disease" adds some background.
  3. Vitamin D—This is critical for proper processing of the calcium and, especially with the misguided recommendation to avoid sunshine (which makes 90% of our vitamin D), is often low.

So what's a mother to do?

The good news is that the overall evidence suggests you can have both a healthy heart and strong bones. If you don't have bone loss (osteoporosis or osteopenia), get your Vitamin D from sunshine (avoid sunburn—not sunshine) and increase your magnesium intake (green leafy vegetables, whole grains, nuts). These and many other key heart and bone healthy nutrients are also in a good multivitamin powder—which I recommend for most everyone to help optimize nutrition and health easily. In addition, walking helps keep both your heart and bones healthy. So walk (out in the fresh air and sunshine) ;-) 30-60 minutes a day.

If you do have loss of bone density (see "Osteoporosis"), take a supplement that supports healthy bones to help build strong bones. This balances the calcium with magnesium, vitamin K, vitamin D, and more—so you can have both a healthy heart and healthy bones.

For those who want more of the technical info…

Vitamin K and Heart Disease

Professors Cees Vermeer and Leon Schurgers, of VitaK, at Maastricht University, the Netherlands, a leading research institute specializing in the role of vitamin K in the field of bone health and cardiovascular health, provided the following statement:

"There are two vitamins known to be involved in calcium metabolism: vitamin D and vitamin K. Increased calcium intake, especially if combined with vitamin D, results in increased absorption of calcium."

"However, vitamin K is required for activation of the vascular protein MGP, which is an inhibitor of calcification. In fact it is the strongest inhibitor of tissue calcification presently known and it is the only calcification inhibitor found in the vasculature. Using highly specific assays, the VitaK research group at the Maastricht University has demonstrated that the vitamin K intake by non-supplemented adults (almost without exception) is insufficient to completely activate MGP (at best 70% is activated). This means that healthy adults are not optimally protected against vascular calcification, even in the absence of an extra calcium load. Subjects of 50 years and older even have a still lower vitamin K status, and hence a higher fraction of their MGP is synthesized in an inactive form."

"When knowing these facts, it is only to be expected that an increased calcium intake will lead to increased artery calcification. This is what may happen if incomplete supplements are provided. It has been demonstrated in large population-based studies, in experimental animal studies and in cell culture studies that the efficacy of vitamin K2 in vascular calcification protection is far better than that of vitamin K1."

"However, at high intakes even K1 was shown to maintain vascular elasticity in a three-year study. Although a large clinical intervention trial on the cardio-protective effect of K2 at high calcium intakes has not yet been published, all data presently available suggest that supplements containing calcium and vitamin D without K2 are incomplete, and may have unexpected adverse side effect in the cardiovascular area."

A 2004 study published in the Journal of Nutrition, called the "Rotterdam Study," followed over 4,800 people for a ten year period. The study found increased intake of specifically vitamin K2 from dietary sources significantly reduced the risk of CHD mortality by 50% as compared to low dietary vitamin K2 intake.

Vascular Events in Healthy Older Women Receiving Calcium Supplementation: Randomised Controlled Trial

BMJ, doi:10.1136/bmj.39440.525752.BE (published 15 January 2008)
Mark J Bolland, P Alan Barber, Robert N Doughty, et al

Objective: To determine the effect of calcium supplementation on myocardial infarction, stroke and sudden death in healthy postmenopausal women.

Design: Randomised, placebo controlled trial.

Setting: Academic medical centre in an urban setting in New Zealand.

Participants: 1,471 postmenopausal women (mean age 74): 732 were randomised to calcium supplementation and 739 to placebo.

Main outcome measures: Adverse cardiovascular events over five years: death, sudden death, myocardial infarction, angina, other chest pain, stroke, transient ischaemic attack and a composite end point of myocardial infarction, stroke or sudden death.

Results: Myocardial infarction was more commonly reported in the calcium group than in the placebo group (45 events in 31 women vs. 19 events in 14 women, P=0.01). The composite end point of myocardial infarction, stroke or sudden death was also more common in the calcium group (101 events in 69 women vs. 54 events in 42 women, P=0.008). After adjudication myocardial infarction remained more common in the calcium group (24 events in 21 women vs. 10 events in 10 women, relative risk 2.12, 95% confidence interval 1.01 to 4.47). For the composite end point 61 events were verified in 51 women in the calcium group and 36 events in 35 women in the placebo group (relative risk 1.47, 0.97 to 2.23). When unreported events were added from the national database of hospital admissions in New Zealand the relative risk of myocardial infarction was 1.49 (0.86 to 2.57) and that of the composite end point was 1.21 (0.84 to 1.74). The respective rate ratios were 1.67 (95% confidence intervals 0.98 to 2.87) and 1.43 (1.01 to 2.04); event rates: placebo 16.3/1000 person years, calcium 23.3/1000 person years. For stroke (including unreported events) the relative risk was 1.37 (0.83 to 2.28) and the rate ratio was 1.45 (0.88 to 2.49).

Conclusion: Calcium supplementation in healthy postmenopausal women is associated with upward trends in cardiovascular event rates. This potentially detrimental effect should be balanced against the likely benefits of calcium on bone.

Bolland MJ, Barber PA, Doughty RN, et al. Vascular events in healthy older women receiving calcium supplementation: randomized controlled trial. BMJ 2008; DOI:10.1136/bmj.39440.525752.BE. Available at:

Click here for more details on the study (account registration required to access).

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