Not too long ago, calcium was the least controversial dietary supplement. Millions of people take the mineral calcium, hoping to keep their aging bones strong and prevent osteoporosis-related fractures, which half of all women eventually experience, as do many older men. The main debates were about which form of calcium is best, whether the pills could cause kidney stones and what other nutrients, if any, the supplements should also contain.
However, studies published in the past few years have probably made many people wonder if they should stop taking the pills. First, some studies have linked calcium pills to increased risk of heart disease. And in 2012, the influential U.S. Preventive Services Task Force dropped a bombshell when its draft recommendations concluded that standard doses of supplemental calcium and vitamin D don’t prevent fractures in postmenopausal women. Here's what you need to know.
Calcium and bones. Bones are living, active tissue and calcium is vital for bone health. (Calcium is also needed for many other bodily functions, such as regulating heartbeat and blood pressure, conducting nerve impulses, allowing muscles to contract and helping blood clot.) Bones constantly absorb and release calcium and other minerals, depending on many factors, such as hormones, exercise, genetics and overall diet. From childhood through early adulthood, bones grow in length and width, but then, in middle adulthood, the rate of bone loss exceeds that at which it is made.
Getting adequate calcium from childhood through early adulthood is important for bone health. Some studies have found that consuming calcium in adulthood leads to greater bone density and/ or reduced fracture risk, but others have not. Many factors affect bone health—from genetics, weight-bearing exercise and body size to age at menopause and a wide array of nutrients—so it’s hard to calculate calcium’s effect. And once an older adult has lost bone mass, increasing calcium intake by itself is not likely to have a big effect.
In its 2010 guidelines on calcium, which relate primarily to bone health, the Institute of Medicine (IOM) set the recommended dietary allowance (RDA) for women over 50 and men over 70 at 1,200 milligrams a day from food (preferably) and supplements, and for other adults at 1,000 milligrams. However, research suggests that 800 milligrams a day is enough for many healthy people, particularly those with adequate vitamin D intake and a diet rich in produce and whole grains.
It’s better to get calcium from food than supplements because foods naturally rich in calcium supply many nutrients important for bones and general health. Dairy foods are the leading sources of calcium, though many people have trouble digesting the lactose (milk sugar) in them. Fish with bones, such as sardines and canned salmon, as well as dark leafy greens and most tofu, contain good amounts. And there are lots of calcium-fortified products. However, many people don’t eat calcium-rich foods often, which is why supplements have been recommended to make up for the shortfall.
Calcium and heart disease. In recent years, several studies and one analysis of earlier research have suggested that calcium supplements modestly increase the risk of heart attacks. These clinical trials have had serious methodological flaws, however. For one thing, most were not designed to look at the effect of calcium on heart health.
In 2012, a widely reported observational study of 24,000 Germans, published in the journal Heart, concluded that the risk of heart attack doubled in people taking calcium supplements (but not with dietary calcium). The records on supplement use in this study were inadequate, however, and the number of calcium takers who had heart attacks was small, rendering the conclusions questionable.