Are calcium supplements bad for your heart?
Calcium supplementation is very common, with just over 40% of us taking this supplement daily. Consuming enough calcium is clearly important for your bone health. However, we also know that arteries of the heart can develop blockages (atherosclerosis), which then eventually become calcified over time. Is it possible that too much calcium, particularly in supplement form, is bad for the heart? Are calcium supplements harmful?
Why do we need calcium? How much do we need?
Adequate intake of calcium in incredibly important for our bone health, as well as muscle function, vascular tone, and signaling within our nervous system. Our blood levels of calcium are tightly controlled, with the vast majority of our storage in the bone and teeth. Chronic inadequate calcium intake can lead to osteopenia and osteoporosis (weak bones). There appears to be reduction in risk of fracture with consumption of 1000 to 1200 mg of calcium in combination with vitamin D.
The recommended dietary intake of calcium for the average adult is 1000 mg/day, which increases to 1200 mg/day for women 51 to 70 years of age and all adults >70 years of age.
Where can I get calcium in the diet?
Good sources of calcium include leafy green vegetables, firm tofu, dairy, beans, blackstrap molasses, and almonds. Many foods (such a plant based milks, orange juice, and cereals) are also fortified with calcium.
There are also other things to consider. Absorption is dependent on the total amount of calcium ingested at one time, as well as other foods eaten at the same time. Sodium and caffeine appear to lead to more excretion of calcium, while high levels of oxalic acid (found in some greens like spinach) and alcohol reduce absorption.
Having adequate amounts of vitamin D is also super important for bone health, and actually increases absorption of calcium. Given many of us are deficient in vitamin D, ensuring we have enough vitamin D is one way to improve our calcium intake. Supplementation of vitamin D has not been linked to increased risk for heart disease.
What’s the story with calcium supplementation?
Several observational studies have shown an association between calcium supplementation and increased risk for cardiovascular disease, especially with intakes greater than 1400 mg per day.
Randomized controlled trial data, on the other hand, has been somewhat inconclusive with regards to risk. However, the most recent meta-analysis of a very large number of trials demonstrated that calcium supplements appear to increase risk for cardiovascular disease, especially risk of heart attack. The risk was particularly strong with calcium supplementation alone, and vitamin D may offset some of the increased risk since it enhances calcium absorption. The study also found a stronger association with higher supplement doses (greater than 1000 mg/day) and in men. Finally, those with genetically higher levels of calcium in their bloodstream have higher rates of heart attack and stroke.
Importantly, high calcium intake from food has not shown an association with increased heart disease risk.
Why does calcium supplementation increase risk of heart disease?
It is not entirely clear. These large doses ingested in supplement form may overwhelm a normally very tightly controlled system, which then temporarily increases the blood levels of calcium. This could result in deposition of calcium in the arteries, increased vascular tone leading to high blood pressure, and increased clotting.
The bottom line
In this case, it is quite likely that there is such as thing as too much calcium. For most, it’s likely preferable to meet our recommended daily intake of calcium through dietary intake. You can easily get an idea of how much calcium you are ingesting by using a food tracker or by working with a registered dietitian. If, on average you aren’t getting enough, you can make a conscious effort to obtain more through food sources first. There may be some instances in which the possible risks of calcium supplementation are outweighed by the benefits (such as in individuals with osteoporosis who are not meeting the recommended levels with food alone), and so, as always, it’s a good idea to speak with your doctor about your personal situation. It’s also important to remember that bone health is not just about calcium, but also closely linked to adequate intake of vitamin D and sufficient levels of weight bearing exercise.
