A caution on excess vitamin D

Vitamin D deficiency has been linked in recent years to dozens of conditions, from heart disease to psoriasis, and supplement sales have increased so fast you'd think they were magic pills. But too much of anything can be problematic, a point made Wednesday by researchers who have also found benefits from the "sunshine vitamin."

For their study, which was presented at the American Heart Association conference in Orlando, Fla., researchers at the Intermountain Medical Center in Utah examined the records of more than 132,000 cardiology patients. They found that the risk of developing atrial fibrillation, a dangerous heart condition, was 2-1/2 times greater for those patients who had what they called "excess" levels of vitamin D in their blood compared with those who had less.

They defined "excess" as higher than 100 ng/mL, a blood level that most Americans could reach only by taking supplements containing more than 10,000 IU per day - 15 times the current federal dietary guideline.

There is no medical concensus on a "normal" blood level of vitamin D. These researchers defined it as 41 to 80 ng/mL. That range, far above what most doctors suggest, is in line with many holistic practitioners' recommendations.