Taking too much vitamin D can cause atrial fibrillation, according to a new study presented at the American Heart Association annual meeting this week.
Vitamin D is created in the body when a person is exposed to sunlight. High levels of vitamin D occur only when people take large quantities of supplements, said Dr. Jared Bunch, the study's lead author and director of electrophysiology research at the Intermountain Medical Center in Murray, Utah. Vitamin D supplements, which have become extremely popular, are touted to help protect the bones and heart for those whose bodies not make enough of the vitamin.
In the study involving 132,000 medical center patients, those with high levels of vitamin D in their blood were nearly three times as likely to develop atrial fibrillation -- a condition in which the heart beats too fast and out of rhythm -- as those whose vitamin D levels fell within a normal range.
The recommended daily amount of vitamin D for most people is 600 IUs, according to the National Institutes of Health. Food sources of vitamin D include tuna and salmon. Three ounces of cooked salmon contains 447 IUs of vitamin D.
This effect on heart rhythms is likely reversible, said Dr. Bunch. "If the levels are excessive, I would hope that when they're cut back, the arrhythmias would improve as well," he added.
Atrial fibrillation has been linked to an increased risk of heart attack, stroke, and dementia.