A new study published this week that cast aspersions on calcium supplements has re-opened the debate over the value of calcium for bone health, particularly for postmenopausal women concerned about osteoporosis.

The study brings up issues of food vs. supplement sources, over what a proper bone-health supplement should look like, over bias in scientific studies, and over the best way to attain optimal health as women age.

The study in question  was a re-analysis of data from the Women’s Health Initiative, a study of 36,282 postmenopausal American women. In this particular arm, women were given either 1,000mg/day calcium carbonate and 400 IU vitamin D/day or placebo for 7 years.

Those study results, published in 2009, found 744 women died who supplemented, compared to 807 women who died in the placebo group. The researchers concluded there was a non-significant trend of reduced risk of death from stroke or cancer, with no difference in other causes of death, including coronary heart disease.

The study published this week in the British Journal of Medicine took another look at the WHI data.

Researchers found that women who were taking calcium already at the start of the study were just fine. But women who were not taking calcium supplements at the start of the study (the age range of participants was 51 to 82 years old) suffered a few more deaths.

By itself, there was nothing much to conclude. So the researchers gathered 15 other studies, involving about 29,000 additional women, and came up with a headline: 25 to 30 percent increased risk of heart attacks and 15 to 20 percent increased risk of stroke.

Before you get out of the calcium supplements business, it’s important to note that that 25-30 percent increase, according to the researchers, meant that for every 1,000 patients, taking calcium or calcium with vitamin D “would cause an additional six myocardial infarctions (heart attacks) or strokes and prevent only three fractures.”

The three additional fractures prevented were called a non-issue, while the six additional heart attacks were called significant.