Vitamin D Shows Heart Benefits in Study
By RONI CARYN RABIN
Vitamin D lowered the risk of heart disease in a new study.
Got vitamin D? It may protect you from heart disease.
Vitamin D, of milk fame, is known for helping with calcium absorption and for building strong bones, which is why it’s routinely added to milk. But there is more and more evidence that vitamin D is a critical player in numerous other aspects of metabolism. A new study suggests many Americans aren’t getting anywhere nearly enough of the vitamin, and it may be affecting their heart health.
In the study, researchers looked at tens of thousands of healthy adults 50 and older whose vitamin D levels had been measured during routine checkups. A majority, they found, were deficient in the vitamin. About two-thirds had less vitamin D in their bloodstreams than the authors considered healthy, and many were extremely deficient.
Less than two years later, the researchers found, those who had extremely low levels of the vitamin were almost twice as likely to have died or suffered a stroke than those with adequate amounts. They also had more coronary artery disease and were twice as likely to have developed heart failure.
The findings, which are being presented today at an American Heart Association conference in Orlando, don’t prove that lack of vitamin D causes heart disease; they only suggest a link between the two. But cardiologists are starting to pay increasing attention because of what they’re learning about vitamin D’s roles in regulating blood pressure, inflammation and glucose control — all critical body processes in cardiovascular health.
Earlier experiments in mice that were genetically altered not to respond to vitamin D found that the animals developed high blood pressure and a heart condition called left ventricular hypertrophy. And population studies of humans found higher rates of coronary heart disease and hypertension the further people live from the equator. Vitamin D deficiency is rare in tropical settings because of the strong sunlight, which promotes creation of the vitamin in the skin.
“What we were taught in medical school about vitamin D is that it’s associated with rickets and calcium metabolism,” said Dr. Joseph B. Muhlestein, a researcher with Intermountain Medical Center in Murray, Utah, and one of the authors of the new study. “We cardiologists didn’t worry about it; and we certainly didn’t order vitamin D levels.”
That, however, is changing. “What’s been discovered in the last few years is a significantly greater role for vitamin D,” Dr. Muhlestein said. “There are perhaps 200 different important metabolic processes that use vitamin D as a co-factor.”
The study involved 27,686 patients at the Intermountain Medical Center based in Salt Lake City. Low tobacco and alcohol use rates in that patient population made it easier for researchers to focus on the effects of vitamin D on heart health.
Patients were divided into three groups based on their vitamin D levels: “normal,” for those who had over 30 nanograms per milliliter of blood, “low” for those with levels of 15 to 30, and “very low” for those with levels less than 15.
Those with the lowest vitamin D levels were 77 percent more likely to die during the follow-up, 78 percent more likely to have a stroke and 45 percent more likely to develop coronary artery disease than those with normal levels. They were twice as likely to develop heart failure as those with normal levels. And even those who had moderate deficiencies were at higher risk, the researchers said.
People who were vitamin D deficient were also twice as likely to have diabetes and tended to have more high blood pressure. But being vitamin D deficient was an independent risk factor for poor outcomes, regardless of other risk factors like diabetes, Dr. Muhlestein said.
The next step for researchers is to figure out whether vitamin D deficiency actually causes disease. It’s possible that people who already have an underlying illness spend more time indoors and aren’t exposed to the sun, where they can absorb vitamin D through the skin. It’s also possible that disease processes already under way may affect vitamin D levels.
A clinical trial that randomly assigns participants to take vitamin D supplements or a placebo might be the next step, Dr. Muhlestein said. Researchers at Harvard and Brigham and Women’s Hospital are starting a large trial in January that will test the effects of vitamin D and omega-3 fatty acid supplements on men and women in their 60s.
Dr. Thomas Wang, an associate professor of medicine at Harvard who published an earlier trial on vitamin D deficiency and heart disease, said that whether treating vitamin D deficiency will have a beneficial effect on heart health is still an open question.
“If that does turn out to be the case, it would have pretty profound public health implications,” he said. “Vitamin D deficiency is very common in this country and other developed countries in northern latitudes, where people don’t get much sunlight and spend most of their time indoors.”
Doctors warn that anyone concerned about vitamin D levels should check with a doctor and have blood tests run. Vitamin D supplements are inexpensive and sold over the counter, but excessive amounts of vitamin D can be toxic.
The Institute of Medicine recommends adults under 50 who aren’t getting vitamin D from the sun get 200 international units of vitamin D a day, and that those 50 to 70 get 400 I.U. a day. Elderly people need even more. There is some controversy, however, over optimal amounts. Many doctors are advising their patients to take much higher amounts, such as 1,000 I.U. a day. The American Academy of Pediatrics has already increased its recommendation for supplementing breastfeeding infants to 400 I.U. — vitamin D is one nutrient breast milk doesn’t provide enough of — and the Institute of Medicine will issue updated recommendations in May 2010.