About one kilogram of calcium is to be found in the human body. Approximately 99 percent of it is in bone bound in hydroxylapatite (Ca5[PO4]3OH). Aside from that, the mineral substance is involved in signal conduction in nerve cells, in blood thinning as well as in muscle contraction. How much calcium is needed by the body is chiefly dependent on the bone’s metabolic requirements. This amount is as a rule from 800 to 1200 mg per day. During pregnancy and breast feeding, and following menopause, it can sometimes amount to as much as 1500 mg daily. This requirement can be obtained through a calcium rich diet or through special supplements.
Earlier research findings
Doubts about the positive impacts of calcium preparations were first raised in public in 2010. A working group led by Ian Reid of New Zealand’s University of Auckland evaluated eleven studies taking in a total of 12,000 patients. To sum up: calcium supplements are said to increase heart attack risk by 30 percent – independent of gender, age and form of preparation. If 1,000 people on account of having osteoporosis-related health conditions take calcium in tablet form for five years, this can statistically end up preventing 26 bone fractures; however 14 more participants end up suffering from heart attack, 10 more from stroke and 13 more people end up dying than in the group where people had not taken calcium. One problem nevertheless with this evaluation was that the studies evaluated involved the study of factors such as bone density and fracture rates. Heart attack in contrast was only dealt with by the authors as a side effect.
Other researchers are dedicating themselves to the topic of calcium as well. In 2013 US-researchers at Bethesda (Maryland) for instance closely studied data as part of a prospective cohort study derived from 388,000 US-Americans. According to the study, in the calcium-supplementation group 20 percent more men had died than in the control group after 12 years. The researchers found no correlation between dosage and death rate due to cardiovascular events if calcium was only consumed through food. The reason for this, the researchers assume, is that the continuously high calcium levels promote a deposition of calcium phosphate in blood vessels. Going further, other studies found no evidence for the theory that the risk of atherosclerotic conditions are increased by calcium tablets.
Data via questionnaires and computer tomography
The group led by Erin Michos from John Hopkins University have now studied how calcium preparations have effects on plaque formation. They obtained the data from the multi-ethnic atherosclerosis study, a multi-year research project involving 6 000 participants, in which among others John Hopkins University was also involved. The study was financed by the National Heart, Lung, and Blood Institute and promoted by the National Center for Research Resources and the National Institute of Neurological Disorders and Stroke.
From among the 6,000 participants, at the commencement of the study in 2000 some 2,700 responded to questions on their dietary habits and provided information as to whether they were taking medications and which medications these were. In addition, the calcium deposits in their coronary arteries were measured at the start and at the end of the study (after ten years). The reason for this is that calcium salts such as calcium carbonate can be deposited in tissue. Deposition in bone or tooth for instance is a physiological process. If however the mineral substance is deposited in the arteries, atherosclerotic plaques can build up. Medical conditions such as heart attack or sudden death are the consequence.
Indicators for elevated risk of plaques due to calcium preparations
The participants were categorised into five groups in correlation with the amount of calcium they were consuming daily, either in food or in tablet form. For the purpose of evaluation, the group led by Erin Michos also took into account demographic and lifestyle factors which elevated the risk of cardiac disease (blood pressure, blood sugar levels, smoking, excess body weight among others). Finally they compared the participant group with the highest calcium intake (more than 1400 mg daily) to the group which had the lowest intake of the mineral substance (less than 400 mg per day).
On average the participants in the calcium-rich group consumed about 2100 mg and the calcium-poor group some 300 mg of the mineral substance. According to the authors the risk of calcified arteries was on average lower by 27 percent in the group taking over 1400 mg calcium. Therefore the likelihood of cardiac disease was also reduced by 27 percent.
In the next step, the researchers took into account how the calcium was actually taken in – via food or in tablet form. Taken as a whole, 46 percent of the participants took calcium tablets. In their evaluation the researchers once again took into account both demographic and lifestyle factors.
The outcome: the individuals in the supplement group had a 22 percent higher risk of having calcium deposits in the coronary arteries. Among the participants who lived on a diet of calcium rich foods (over 1000 mg per day), the lowest tendency for heart disease was able to be found. According to co-author Anderson from University North Carolina these results show that the human body reacts differently to supplements than it does to “natural” minerals and makes use of supplements differently. The researchers expressed the assumption that calcium salt in supplements is the reason for the differing outcomes. It could also be possible that a larger amount of the mineral being taken in as one mass via tablet intake is a factor.
Limitations of the study
“Based on these results we can inform our patients that a heart-friendly diet with calcium-rich foods appears not to be harmful; it could even protect the heart. Nevertheless patients definitely should speak to their doctor before planning on taking calcium, about whether it is necessary at all and which dosage is the correct one“, study author Erin Michos states.
It should be noted that studies in which participants are only examined at the start and the end of the study, and only twice studied computer-tomographically, are not especially precise. Moreover it remains unclear how calcium tablets promote plaque formation. This is because other processes underlie the calcification process and ultimately lead to the deposition of the mineral in blood vessels – this also occurring when calcium concentrations in the blood are normal. The correlations uncovered therefore merely represent statistical associations. The mechanism first needs to be demonstrated.