Your doctor may have told you to take calcium supplements to protect your bones and reduce the risk of fractures. A new study in the British Medical Journal may turn that advice upside down.
Researchers pooled the results of 15 medical trials in which a total of about 12,000 people were given calcium-supplement pills. They found that the people taking the calcium had a 30 percent increase in the risk of heart attack compared to those who did not. There was also an insignificant increase in the risk of stroke and death.
The risk of heart attack was greater among those with the highest intake of calcium pills (more than 800 milligrams a day); it was not dependent on the age or sex of the participants, or the type of calcium supplement.
Further, a randomized, controlled trial published in 2008 looked at the effects of calcium supplements on vascular disease. In this study, 1,471 postmenopausal women were randomized to receive Citracal (1,000 mg per day of elemental calcium in divided doses) vs. a placebo for five years.
At the end of the study, the women taking calcium pills had a greater risk of heart attack, stroke and sudden death compared with those taking the placebo; the risk of having a heart attack was about 50 percent higher, the risk of stroke almost 40 percent higher.
Why might calcium increase the risk of vascular disease? Observational studies in the past have suggested that people with higher intakes of calcium actually had a lower risk of vascular disease; this is medically plausible because calcium does seem to slightly increase the amount of good cholesterol (HDL) in the blood and lower the bad cholesterol (LDL).
However, we know that calcium can also cause mischief in our arteries; those of you who have had a CT scan of your heart to screen for heart disease know your assessed risk is based on your calcium score.
When our arteries are inflamed from poor diet, obesity, smoking and couch-potato lifestyles, calcium is pulled into that inflamed area from the bloodstream. It then gets laid down in the blood vessels, leading to atherosclerosis or hardening of the arteries. Hence, a higher calcium score on a CT scan implies more disease in the arteries that feed the heart.
So is all calcium problematic? The studies above involved people who took calcium pills. What about foods that are high in calcium – do they increase your risk of heart disease, too? Probably not.
When you take a calcium pill, this leads to an acute increase in blood-calcium levels, and this rapid increase likely delivers more calcium to your arteries, where it can cause damage. Calcium in food, on the other hand, is absorbed much more slowly and does not lead to a significant change in blood levels; hence it does not seem to cause the problems that pills do.
So what’s the bottom line? Your food is your medicine. Eat a wide variety of plant foods, including dark-green leafy veggies, whole grains, legumes, nuts and seeds, all of which contain calcium (e.g., 1 cup of cooked broccoli has 180 mg of calcium).
You can also protect your heart health and bone health by limiting your intake of animal food and salty foods – not only are these associated with a higher risk of heart disease, they also accelerate bone loss.
In fact, a study from Yale in the 1990s looked at fracture rates in 16 countries around the world and found that people in countries with the lowest intake of meat, eggs, fish and dairy products also had the lowest fracture risk – another reason to eat more veggies and less meat.