LOS ANGELES - Raising the amount of vitamin D in the blood appears to help some people, at least those deficient in the vitamin, reduce their risk of heart disease by about 30 percent, researchers announced yesterday. The findings, though preliminary, support further investigation of the interplay between vitamin D and heart health.
Observational studies have linked heart disease with low vitamin D levels in the blood and, in recent years, studies have shown that as many as three-quarters of Americans have a concentration in their blood that is under the normal level of 30 nanograms per milliliter.
But it has been unclear whether people with low vitamin D levels have more heart disease because of the vitamin deficiency or for other reasons, such as lack of exercise, said Dr. J. Brent Muhlestein, the lead author and director of cardiovascular research at Intermountain Medical Center Heart Institute in Salt Lake City. He announced the findings at the American College of Cardiology meeting in Atlanta. "The question we looked at is, if you do something about it, like taking vitamin D supplements, does that reduce the risk?"
Researchers have been uncomfortable randomizing people with low vitamin D into a group that receives supplements and a group that does not because, in theory, every vitamin D deficiency should be treated.
Low vitamin D levels can contribute to weaker bones and have been associated with increased risks of diseases, including several types of cancer.
Instead, Muhlestein's group examined data from more than 9,000 people who had been diagnosed with low vitamin D and who had a blood sample taken at a later date. About half the people had normalized their vitamin D blood levels by the time of the second blood sample, and they showed much less heart disease compared with people whose levels were still below normal.