Harvard Health Letter

Should I take vitamin D?

Ask the doctor

Q . I am 68 and in excellent health. I eat a healthy diet, exercise every day, and do not drink or smoke. I'm on no medicines. The only pill I take is vitamin D. But I'm wondering: is there any benefit in that?

A. In a nutshell, here's what we know. Our skin makes most of the vitamin D in our bodies after exposure to sunlight. Because most of us are indoors most of the 24 hour day, many of us have relatively low blood levels of vitamin D.

Studies have found that people with low blood levels of vitamin D are at greater risk for several important diseases including heart disease, some kinds of cancer, and autoimmune diseases than people with higher levels of vitamin D. So it seems logical that taking a vitamin D pill that will raise your blood levels of the vitamin would be a good thing.

But the only way to prove that such higher levels bring health benefits is to perform a large randomized study in which some people take vitamin D every day and some take an identical-looking sugar pill (placebo). Such a study is under way, and preliminary results are expected within two to three years.