The Dark Side of Calcium Supplements

Calcium is one of the most important supplements when it comes to osteoporosis.

Women undergoing menopause have a far greater risk of developing it due to hormonal changes. Osteoporosis which literally means “porous bone,” is a disease that weakens bones, increasing the risk of fractures. It results in an increased loss of bone mass and strength. The progression of the disease is often without any symptoms or pain. In fact, the lack of oestrogen is one of the biggest factors in osteoporosis development. There is a direct relationship between the lack of oestrogen during perimenopause and menopause and the development of osteoporosis. Early menopause (before the age of forty-five) and any prolonged periods in which hormone levels are low and menstrual periods are absent or infrequent can cause significant loss of bone mass.

One of the suggested treatments to help prevent and stabilize osteoporosis is calcium supplements (of course together with specific drugs that help drive calcium into the bones). Recently though, a rising body of evidence on the adverse effects of calcium supplementation on non-skeletal (therefore not related to bones), especially cardiovascular, health has been a cause of increasing concern. In fact, a significant number of studies have reported a direct association between calcium supplementation and adverse cardiovascular events, even though high dietary calcium intake was shown to have a protective effect. Here is the peculiar result: a high calcium diet has a protective effect, but taking supplements has not.

The most surprising data though, is the fact that there is not enough supporting scientific evidence that calcium supplements increases bone health in the general population.

Even though there is an established role of calcium supplementation in the prevention of osteoporosis, available evidence supporting its role in the prevention of fractures is weak and inconsistent among many different studies. While some findings, mostly drawn from vitamin D–deficient patients (we’ll talk about the correlation between calcium, vitamin D deficiency and osteoporosis in another article), showed a small or marginal effect of calcium supplementation on bone loss and a risk of total fracture, others reported no reduction in hip fracture risk with calcium supplementation and a neutral effect for non-vertebral fractures. In fact, the idea behind calcium supplements is that it should “enter” the weakened bone and build it back. There is a big lack of evidence that taking supplements increases the “migration” of circulating calcium to the bone compartment.

For instance, in a recently published review, calcium supplementation was found to be neither harmful nor beneficial. There was a lack of dose?response benefit for calcium supplementation (in those studies where the dose was provided), doubting the common thinking that “more is better.” Given that, there is growing consensus within the scientific community suggesting that widespread prescription of calcium supplements to prevent fractures should be put aside since there is not sufficient scientific evidence on the benefits of it in the general population. Recently, there has been an increased interest in the non-skeletal related outcomes of taking calcium supplements, including cardiovascular health, and consequently its relationship with cardiovascular mortality.Most studies agree on the fact that adequate dietary (therefore just from food and a balance diet) calcium intake is important for bone health and major physiologic functions. Many studies have shown an increase in cardiovascular risk and mortality associated with calcium supplementation but not from high dietary calcium intake. Therefore, it is generally admitted now, that dietary calcium intake seems to be safer compared with calcium supplementation.

Until now, little evidence existed for biological mechanisms linking calcium supplementation to atherosclerotic related heart disease.

More recently, the National Osteoporosis Foundation and the American Society for Preventive Cardiology asked an expert panel to evaluate the effects of dietary and supplemental calcium on cardiovascular disease based on already existing scientific literature. According to the experts, there was some evidence that calcium with or without vitamin D intake from food or supplements has a relationship (of any type, beneficial or harmful) with the risk of cardiovascular and disease mortality. Considering then available evidence, their conclusion was that calcium intake from food and supplements, not exceeding the upper level of intake (defined as 2000–2500 mg/d) should be considered safe. Safe does not mean that it has an effect. However, another study suggests the opposite. In fact, they provided evidence of association between the risk of Coronary Artery Calcification (CAC) and calcium intake, both dietary and supplementary, in a large cohort of patients involving 2742 participants, without cardiovascular disease. They also found that calcium supplements used regularly was associated with a 22% increase in risk of incident CAC. In addition, other research evaluated the association of dietary calcium intake and calcium supplementation with Myocardial Infarct (MI), stroke risk, and overall cardiovascular disease mortality. They showed that after an average follow?up of 11 years, in comparison with non-users of any supplements, users of calcium supplements had a statistically significantly increased MI risk, which was more pronounced for people using calcium supplements only. These studies and all this data taken together, suggests that maybe a long?term consumption of supplements might increase the risk of atherosclerosis and therefore MI. On the contrary, there might be a protective effect of total calcium intake on incident coronary atherosclerosis, especially among non-supplement users. Indeed, patients achieving high calcium intake with lower dietary proportion and higher supplement use, present the greatest risk of coronary atherosclerosis and potentially MI. This is then, of incredible importance because more patients with high calcium needs such as the elderly, rely mostly on regular consumption of high doses of calcium supplements to fill their daily needs, instead of trying to cover it with diet.

These findings clearly show that, increasing calcium intake should be done by increasing dietary intake, not using a supplement that seems to have a harmful effect on cardiovascular health.

Thus, the widespread use of calcium supplements, mostly in older individuals, is not a beneficial way to meet the growing needs of calcium with age and should indeed be substituted. Other studies though, show that calcium supplements are beneficial in the prevention of osteoporosis and osteoporosis related fractures. To summarize, recently published data suggest a significant increase in CAC and cardiovascular diseases with calcium supplementation. Some other studies instead, document the benefit of having good levels of calcium for preventing osteoporosis related fractures. These new evidences stress the need for an evidence?based approach to calcium supplementation. Moreover, it is urgent now to educate health care providers on the possible risk of excessive and also unnecessary calcium supplementation. From a cardiovascular point of view, dietary calcium intake by eating foods high in calcium appears safer than calcium loading with supplements, so in summary, it seems to be better to follow a balance. Further studies are necessary to have a clear answer but in the meantime, it is probably better to double check with a specialist before taking this kind of supplements.

Guest Post by Dr. Ornella Capillari 


J Clin Hypertens (Greenwich).2017 Jun;19(6):640-646. doi: 10.1111/jch.13010. Epub 2017 May 2. Calcium supplementation and cardiovascular risk: A rising concern.

Tankeu AT1, Ndip Agbor V2, Noubiap JJ3.

Curr Atheroscler Rep. 2017 Jan;19(1):5. doi: 10.1007/s11883-017-0637-2. Vitamin D, Calcium, and Cardiovascular Disease: A”D”vantageous or “D”etrimental? An Era of Uncertainty.Chin K1, Appel LJ2,3, Michos ED4,5,6.

Heart. 2012 Jun;98(12):920-5. doi: 10.1136/heartjnl-2011-301345. 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). Li K1, Kaaks R, Linseisen J, Rohrmann S.

Clin Interv Aging. 2018; 13: 2443–2452. 

Published online 2018 Nov 28. doi: 10.2147/CIA.S157523The good, the bad, and the ugly of calcium supplementation: a review of calcium intake on human health. Kelvin Li,1,*Xia-Fang Wang,2,3,*Ding-You Li,4Yuan-Cheng Chen,2Lan-Juan Zhao,1Xiao-Gang Liu,5Yan-Fang Guo,6Jie Shen,2Xu Lin,2Jeffrey Deng,1Rou Zhou,2and Hong-Wen Deng1,7