Calcium supplements have been considered for years as something almost taken for granted. Doctors often recommend them to maintain bone health, prevent deficiency, and especially in older age or in conditions of osteoporosis. But a new and large study raises a troubling question: It is possible that in people who already suffer from cardiovascular disease, calcium supplements may be associated with a higher risk of another cardiac or cerebrovascular event.
The study, published in the Journal of the American Heart Association, examined whether taking calcium supplements is associated with an increased risk of recurrence of cardiovascular events in people who have already experienced significant heart disease. The researchers’ conclusion was fairly clear: Among patients with existing cardiovascular disease, the use of calcium supplements was associated with an increased risk of recurrent events. The association was especially prominent when calcium was taken alone, without vitamin D.
This is particularly important because this does not involve healthy people at low risk, but rather a population that is already at high risk to begin with: People who have had a myocardial infarction, stroke or coronary heart disease. For them, any small addition in risk has real significance.
What exactly did the researchers examine?
The researchers conducted a large retrospective population study in Hong Kong. They examined people aged 40 and older who were first diagnosed with significant cardiovascular disease between the years 2006 and 2015. After statistical adjustment intended to make the groups as comparable as possible, the final analysis included 17,720 patients who received a prescription for calcium supplements and 17,720 similar patients who did not receive calcium supplements at all.
The researchers then followed the participants over time and examined who among them experienced a recurrent cardiovascular event. The events included another heart attack, stroke, an event of coronary heart disease, as well as hospitalization or an emergency room visit for a cardiovascular reason.
The results were concerning: Taking calcium supplements was associated with a 10% increase in the risk of recurrence of major cardiovascular events. In addition, there was a 16% increase in the risk of hospitalization or an emergency room visit due to a cardiac or vascular cause. When the researchers examined the types of events separately, they found an increased risk of recurrence of each of the following: Heart attack, stroke and coronary heart disease.
But one of the most interesting findings was that not all calcium supplements appeared the same.
When calcium was given alone, without vitamin D, the risk was clearly higher: An increase of 21% in the risk of recurrent cardiovascular events. In contrast, when calcium was given together with vitamin D, no statistically significant increase in risk was found.
It is important to emphasize: This does not mean that vitamin D definitely “protects” against the risk. This is an observational study, and not a randomized study that proves causality. But the difference between calcium alone and calcium combined with vitamin D was one of the most prominent findings in the article.
The researchers also found a difference between men and women. In men who took calcium supplements, a 15% increase in the risk of recurrent events was observed, compared to an increase of only 7% in women.
Why might this happen?
One of the hypotheses raised by the researchers is that calcium supplements cause a relatively rapid increase in blood calcium levels after intake. Some researchers believe that these “spikes” in calcium levels may contribute to clotting, calcification of blood vessels and processes related to atherosclerosis. That is, it is possible that not only the amount of calcium is important, but also the way it enters the bloodstream.
Vitamin D, according to the researchers’ possible explanation, may change the picture because it is involved in the absorption and regulation of calcium, and may also have a beneficial effect on the blood vessel wall. Therefore, when there is already a medical need for a calcium supplement, the combination with vitamin D may be less problematic than taking calcium alone.
Another important finding was that the higher the dose, the higher the risk. In the study’s sensitivity analyses, the highest risk was observed at daily doses of 1,000 mg of calcium and above, especially when it involved calcium without vitamin D.
Still, it is important to clarify the limitations of the study. This is an observational study, and therefore it is not possible to determine unequivocally that the calcium supplement itself caused the recurrent events. In addition, the researchers did not have complete information on the use of supplements purchased without a prescription, nor full data on calcium intake from food. The implication is that it is not possible to know with certainty whether the problem is the supplement itself, the total calcium load, or a combination of several factors. Beyond that, the study was conducted in Hong Kong, in a population with different dietary characteristics from other populations.
Even so, this is a very important study, because it shines a spotlight on a group that is usually not considered when talking about supplements: People who are already living with cardiovascular disease. For them, what seems like an innocent supplement for maintaining bone health may be less innocent than we thought.
What does this mean for you?
First, there is no reason here to panic and stop all calcium supplements across the board. There are patients who truly need it, especially in conditions of osteoporosis or as part of certain drug treatments. But there is definitely a reason here to stop treating calcium supplements as something “safe for everyone” without further thought.
Especially in people with a history of heart attack, stroke or significant heart disease, it is not advisable to start a calcium supplement on their own. It is important to consult a doctor, check whether there is a real need for the supplement at all, whether calcium from food can be preferred, what the appropriate dosage is, and whether it is right to combine it with vitamin D.
Ultimately, this study reminds us of an important point: Even familiar, available and very common supplements are not necessarily risk-free. A supplement that is “natural”, “routine” or “sold without a prescription” is not necessarily safe for everyone.In people with existing cardiovascular disease, calcium supplements appear to require much more caution, more personalization, and much more medical consideration than is sometimes assumed.
Dr. Dalit Draiman-Medina is a specialist in family medicine and integrative and functional medicine
Source:
www.jpost.com
