Vitamin D is dandy, so long as you don't overdo it

Vitamin D, in combination with calcium, is good for your bones. You should consume modest amounts in your diet, if possible (and for most people, that is quite possible), or in the form of supplements if you can't get enough via food and drink.

But somehow we've arrived at a point when some physicians are prescribing large doses of vitamin D supplements for their patients in the hope of preventing cancer, cardiovascular disease, diabetes, autoimmune disorders, and other maladies, despite a lack of evidence that it works, according to a new commentary in the Journal of the American Medical Association. Other people are loading up on vitamin D on their own.

"Clinical enthusiasm for supplemental vitamin D has outpaced available evidence on its effectiveness," wrote JoAnn E. Manson and Shari S. Bassuk of the Division of Preventive Medicine at Brigham & Women's Hospital in Boston.

This practice is not totally harmless. You should be consuming 600 international units daily if you are between the ages of 1 and 70, and 800 IUs each day if you're 71 or older, according to the Institute of Medicine, the health arm of the National Academy of Sciences. These amounts are enough for 97.5 percent of U.S. and Canadian residents, the institute says. (Sunlight stimulates production of vitamin D for people in sunnier climes.)

Go above 4,000 IUs, unless there's a specific reason for needing that amount, and you risk kidney stones, calcification of blood vessels, and possibly the very cardiovascular disease you were seeking to prevent, Manson said in an interview.

- Washington Post