Do food sources trump supplements?
Calcium is recommended as a way to help prevent osteoporosis, but calcium supplements have come under attack recently due to a possible heart attack risk. A study in the June issue of Heart found a significantly increased risk of heart attack among women taking calcium supplements. Two other studies, in 2010 and 2011, had similar results. Since so many people take the supplements, these studies have received a lot of attention.
But Dr. JoAnn Manson, chief of preventive medicine at Harvard-affiliated Brigham and Women’s Hospital, questions the link and notes that such risks haven’t been found with calcium-rich foods. “Although I think the jury is still out on the supplement issue, it would be wise to try to get most of your calcium from food sources if possible,” she says.
Calcium in arteries
Image on the left shows a coronary artery without calcium; calcium shows up as white patches in the image on the right.
How much should you take?
Current guidelines for calcium intake for bone health recommend between 1,000 and 1,200 milligrams (mg) per day, depending on your age and gender. You can get it from a supplement, from your food, or both. Calcium from dietary sources benefits health. “The calcium-rich diet has been linked to a reduced risk of cardiovascular disease, diabetes, metabolic syndrome, and hypertension. Dietary calcium has not been linked to any increase in risk of cardiovascular events,” Dr. Manson says.
Why would calcium from dietary sources be heart healthy, but not calcium from supplements? Researchers have proposed that digesting calcium supplements might cause a surge in blood calcium levels. The calcium could accumulate in your arteries, making them rigid—which contributes to chest pain, high blood pressure, and heart attacks. Calcium may also build up inside artery plaques, little pockets of cholesterol that can block your blood flow or burst, causing a heart attack or stroke. But again, Dr. Manson notes that the evidence isn’t solid. “The evidence that calcium supplements are leading to increased calcification of plaques is not well established. There’s clear evidence that coronary artery calcium is a marker for increased risk of heart disease, but there’s also evidence that plaques with calcium may be more stable and less likely to rupture.”
Dr. Manson says the real risk is when people exceed the daily recommended intake. “On average in the US, women get 700 mg of calcium from dietary sources, so most women would need 500 mg or less in calcium supplements. However, many women also take supplements of 1,000 mg or more. This is concerning because high doses of calcium supplements have been linked to kidney stones as well.”
Calcium and vitamin D
Whether you get your calcium from food or a supplement, make sure you get adequate vitamin D to help with calcium absorption: The Institute of Medicine recommends 600 IU per day for all adults 70 and younger. Adults older than 70 need 800 IU daily. Fortified dairy products are also a good source of vitamin D.
What you should do
Dr. Manson says it’s vital to get your daily recommended dose of both calcium and vitamin D, even if you already have heart disease. Good sources of calcium include milk, cheese, yogurt, soy products, sardines, canned salmon, fortified cereal, and dark leafy greens such as kale and collard greens. “Read food labels and you’ll see that it’s feasible to reach 1,000 mg of dietary calcium a day,” says Dr. Manson.