Vitamin D holds promise for many things, like building bone, preventing heart attacks and strokes, reducing cancer risk, and more. But that promise isn’t fully backed by science. For example, a controlled clinical trial published this week in JAMA Internal Medicine found that a vitamin D supplements didn’t build bone in postmenopausal women with blood levels of vitamin D below the threshold generally considered necessary for good health. Many researchers are looking ahead to results from an ongoing trial called VITAL, which aims to gather the kind of solid evidence that will let us know for sure whether taking relatively high doses of vitamin D can ward off heart attack, stroke, or cancer. The results are expected by the end of 2017. It’s also possible to get vitamin D the old-fashioned way: go out in the sun between 10 a.m. and 3 p.m. with at least 10% of your skin exposed. Stay out long enough to absorb the sun but not long enough to be burned.
For the past few years, vitamin D has been gaining a reputation—not entirely earned—as a wonder vitamin that offers protection against some cancers, bone-weakening osteoporosis, heart attack, Alzheimer’s disease, and other chronic conditions. Not so fast, caution two reports in the journal BMJ. One concluded that “highly convincing evidence of a clear role of vitamin D does not exist for any outcome.” The other showed a link between low blood levels of vitamin D and increased risks of dying prematurely from cardiovascular disease, cancer, and other causes. But it isn’t clear if low vitamin D causes chronic conditions, or whether chronic conditions cause low vitamin D levels. To play it safe, get the amount of vitamin D recommended by the Institute of Medicine: 600 IU of vitamin D a day for everyone ages 1 to 70 and 800 IU for those 71 and older. Eating foods rich in vitamin D or getting a few minutes of sunshine a day can do the trick.