Top 3 Risks of Calcium Supplements

By Charles Li MD

Data visualization of the top 3 risks of calcium supplements. These include heart attack, stroke, and kidney stones

While taking calcium pills to increase your calcium sounds healthy and safe, recent clinical trials have highlighted several serious side effects of calcium supplement pills.

We’ve known for decades that getting enough calcium in your diet is essential for good health and strong bones. A lifetime of higher dietary calcium intake is associated with a lower risk of bone fractures. Calcium and Vitamin D effectively strengthen your bones which keeps your bones from getting fragile with aging.

The Dangers of Calcium Supplements

However, recent studies have shown that calcium supplement pills are potentially dangerous.

Unlike dietary calcium, calcium supplements may increase your risk of heart attack, stroke, and kidney stones.

In order to study the effects of calcium supplements, the Women’s Health Initiative randomized over 35,000 women to take either calcium supplements or a placebo (an empty pill). They then followed the women to see whether patients who took calcium supplements were more likely to suffer serious health consequences.

Heart Attacks and Calcium Supplements

An analysis of the data published in the BMJ, one of the top medical journals, found that women who took calcium supplements had a significant increase in their risk of heart attacks. They estimated that patients who were on calcium supplements had an approximately 20% increase in heart attacks.

Data on Calcium Supplements and Heart Attacks

While the initial study did not show a significant increase, a reanalysis by this team found that this was due to the many patients taking calcium supplements “on the side.” Once these were excluded, the heart attack risk was found to be statistically significant.

Typically, a randomized controlled trial of this size and significance would be rated at a 5 star level by our quality metrics. However, this particular data received a 4/5 star rating because this number was obtained through analysis after the fact. This represents a solid study that while not perfect, should be reliable and trusted.

Stroke Risk and Calcium Supplements
Data on Calcium Supplements and Strokes

The same study also looked at stroke risk, as heart attack and stroke risk are correlated and often arise from the same biological processes.

Similar to the heart attack data, the researchers found a significant increase in stroke risk in patients who took calcium supplements. They estimated this risk increase to be around 19%.

Since this data was also only obtained after analysis after the fact, this data receives a rating of 4/5 star quality rating.

Kidney Stones and Calcium Supplements
Data on Kidney Stones and Calcium Supplements

The Women’s Health Initiative data found a small increase in the risk of kidney stones in patients randomly assigned to take calcium among the many side effects studied.

Since this data is of relatively modest significance and magnitude, we assign this a 3/5 star rating. The study and the data appear reliable. However, the data is not strong as kidney stones were not the primary objective studied.

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