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Depending on its source, calcium may affect heart health differently. Research from 2016 found that, while high calcium intake from food may reduce the risk of coronary artery calcification (CAC, a risk factor for coronary-artery disease), calcium intake from supplements may increase the risk of CAC. Published in the Journal of the American Heart Association, the study included data from 5,448 adults, aged 45 to 84, without cardiovascular disease. The participants answered food frequency questionnaires and submitted a medication inventory, which the researchers analysed for dietary and supplemental calcium intake. The researchers also tested the participants for CAC at the beginning of the study and during a ten-year follow-up. They found that:

• Participants with the highest total calcium intake (1,454 mg per day or more) had a 27% lower risk of CAC than those with the lowest total intake (435 mg per day).
• However, the use of calcium supplements was associated with a 22% increased risk of CAC compared with those not taking supplements, suggesting that only calcium from food was protective.
• Further analysis revealed that participants with the lowest risk of CAC were non-supplement users with the highest total calcium intake, and participants with the highest risk of CAC were supplement users with the lowest total calcium intake.

Why the difference between dietary and supplemental calcium? The researchers think that excess calcium in the blood due to calcium loading—taking an excessive amount of calcium in one dose—might end up being deposited in tissues throughout the body, including blood vessel walls. They also noted that the highest calcium intake (2,157 mg per day) was nearly double the recommended daily allowance, and that while calcium is an essential nutrient, this may be an example of too much of a good thing. On the other hand, other studies have confirmed the safety of calcium supplementation, so more research is needed to substantiate the latest findings. In the meantime, no one doubts the importance of adequate calcium intake through food.

Source: Journal of the American Heart Association