The first of two studies to show a link between calcium and increased heart disease was published last year from the University of Auckland in New Zealand (British Medical Journal 2011; April 19th). This meta-analysis reported there was an increased risk for myocardial infarction (heart attacks) in women who took calcium supplements. The study’s results are questionable. For one thing, a meta-analysis is a statistical method that combines results from several trials that have investigated a similar issue. Because many nuances and details are lost in the process, it is not uncommon for studies included in a meta-analysis to come to one conclusion, but when combined, the meta-analysis finds the opposite. In short, a meta-analysis is a start, but not the final word. In this meta-analysis, the researchers removed angina from cardiovascular endpoints studied, yet a previous study by the same authors had found calcium reduced this chest pain associated with reduced blood flow to the heart. Hmm. In addition, the risk of heart attach was statistically significant only at low to moderate calcium supplementation, not at high levels. In fact, people who supplemented with more than 1,000 milligrams of calcium a day had a lower rate of death from all causes. This implies that high intake of supplemental calcium is protective overall, but low to moderate is harmful to the heart.
In the second study, researchers at the University of Zurich found that dietary calcium was protective against heart disease, but calcium supplements raised heart attack risk, while people whose calcium intakes from all sources, dietary and supplemental, was approximately 820 milligrams a day had a lower risk of heart attack, compared to those whose intake was less. (Heart 2012;98:920-925). These contradictory results suggest there are confounding factors not address in the studies. For example, perhaps people at risk for heart disease take supplements in hopes of reducing their risk, so the disease precedes the supplement.
Granted, neither of these studies proved a cause-and-effect relationship, but there is the slim possibility that abrupt changes in blood calcium concentrations that might occur with large single doses of supplemental calcium could contribute to cardiovascular effects. That means anyone eating 2 cups of Greek yogurt at one sitting is at risk, too. Besides, our intestines can absorb a maximum of 500 milligrams of calcium at a time. So, moderate doses up to this level, from food or supplements, is well within its ability to “cope.”
Let’s put this new information into perspective. Thousands of studies show that people who consume ample calcium, either with supplements or in food, are at lowest risk for osteoporosis, a disease that affects more people than the combined incidence of heart disease, heart attack, and stroke. The researchers in both studies concluded that people should get their calcium from food, but the very reason for taking supplements is that many people aren’t getting their calcium from food, so to take away their primary source of this vital mineral is putting them dead center in the path of bone loss, and possibly colon cancer, hypertension, and more.
The bottom line? Everyone needs 1,000 milligrams to 1,500 milligrams of calcium daily. Choose food first, then fill in the gaps with a moderate-dose supplement, and rest assured you are doing your body good.