Vitamin D's cancer benefits questioned

WASHINGTON — A large new study found no sign that vitamin D lowers the overall risk of dying from cancer.

The exception: People with more vitamin D in their blood had a significantly lower risk of death from colorectal cancer, supporting earlier findings.

Getting enough of the so-called sunshine vitamin — the skin makes it from ultraviolet rays — is vital for strong bones.

But vitamin D has made headlines in recent years because of research saying it may be a powerful cancer fighter, sparking a push for people to get more than recommended amounts, either through diet or sun exposure.

The first-of-a-kind government study released Tuesday shows the issue is not settled.

National Cancer Institute (NCI) researchers analyzed vitamin D levels measured in almost 17,000 people as part of a national study that tracked their health. About a decade after enrolling, 536 of those people had died of cancer.

Whether people had low or high vitamin D levels played no role in their risk of dying from cancer in general, researchers reported Tuesday in the Journal of the National Cancer Institute.

The NCI's study is the first to compare blood levels of vitamin D to cancer mortality, and "it's the best research we have on this topic," said Dr. Len Lichtenfeld of the American Cancer Society.

But a big weakness: It measured vitamin D at just one point in participants' lives, when levels can vary widely with dietary changes and especially the seasons.