Low vitamin D levels are common and are linked to a number of risk factors for cardiovascular disease, new evidence suggests. Heart attacks and premature death also are connected with low levels, but it's still too early to know for sure whether popping a daily vitamin D supplement or bolstering your diet with D-rich foods can cut your risk for heart problems.
"This isn't original research, but it's a very extensive review of the existing literature. There's evidence low vitamin D levels affect blood pressure, insulin resistance, coronary artery disease," says lead author Carl "Chip" Lavie, medical director of preventive cardiology at the John Ochsner Heart and Vascular Institute in New Orleans.
The review of more than 75 previous studies, most of which were observational, ran in today's Journal of the American College of Cardiology.
Lavie says the big question left now is how much vitamin D is effective for preventing or reversing the risks for cardiovascular disease.
"The only thing that's going to settle the controversy is randomized trials," he says.
JoAnn Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital, agrees: "We need randomized clinical trials to know if the benefits of high doses of vitamin D outweigh the risks. There's a long history of randomized trials overturning the dogma of observational studies."
To address the question, last year Manson launched the VITAL study of 20,000 men and women. The study is looking at whether taking daily dietary supplements of vitamin D3 or omega-3 fatty acids reduces the risk for developing cancer, heart disease and stroke.
Half of Manson's study participants will take 2,000 international units (IUs) of vitamin D3 a day, and the control group will be given a placebo. Results should be out in about five years.
"Until we see the results of the VITAL study and other similar large trials, I think most clinicians would say if you have very low D levels, we'll give you supplements, but whether that will help the cardiovascular system is far from certain," says Roger Blumenthal, director of the Johns Hopkins Ciccarone Preventive Cardiology Center.
Getting your daily dose
Recommended daily intake of vitamin D:
70 or younger -- 600
Over 70 -- 800
Vitamin D-rich foods include:
Fatty fish such as salmon
Fortified dairy products, juices and cereals
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