Don't expect your calcium and vitamin D supplements to improve your heart health or prevent a stroke, according to a systematic review of published studies.
While vitamin D and calcium are clearly important for bone health, write the authors of the review, evidence on whether they help heart health is conflicting.
In the U.S., the recommended daily intake of calcium is 1000 milligrams and 400 international units for vitamin D. Skin produces vitamin D when directly exposed to the sun, but this is usually not enough.
Milk, breakfast cereals, and orange juice fortified with the vitamins are the main food sources, though some fatty fish naturally contain high amounts of vitamin D.
Before people who already get enough start taking vitamin D and calcium supplements, senior author Dr. Howard D. Sesso, from Brigham and Women's Hospital in Boston, and his colleagues wanted to study the evidence to support their use — and make sure there are no hidden risks involved.
"The existing literature is quite sparse" in this area, Sesso told Reuters Health.
None of the 17 studies they uncovered was designed specifically to look at effects of the supplements on heart disease, heart attack, stroke, or death due to related causes.
"Existing trials were designed with other purposes in mind," Sesso explained.
Part of the difficulty in looking at the overall picture was that forms and doses of the supplements differed from one study to another.
Some studies did show that vitamin D supplements cut the risk of dying from heart disease and stroke. However, most of these involved patients with severe kidney disease who were on dialysis, a vast difference from healthy individuals, Sesso noted.
The remaining studies failed to show any meaningful benefits of vitamin D, calcium, or a combination of the two.
So at this time, Sesso says "no" to suggestions that healthy people supplement their diet with calcium or vitamin D.
"Now, if there are specific instances of vitamin D or calcium deficiency, then that's a separate issue that should be discussed with a personal physician," he added.
There are historical lessons about taking supplements, authors of a related editorial warn. For several years, vitamins A and E were believed to prevent multiple ills, ranging from heart disease to cancer. However, major reports that came out in 2005 and 2007 showed that both vitamins actually increased the risk of dying.
"We've learned in the past that things can go really, really wrong" when people start taking vitamin pills, Dr. Eliseo Guallar, lead author of the editorial, told Reuters Health.
Guallar, from Johns Hopkins Bloomberg School of Public Health in Baltimore, and Sesso agree that the best way to avoid a similar outcome is through "good, solid" studies in healthy populations.
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