Vitamin D and its good and bad effects on the heart

By Dr. Ananya Mandal, MDNov 17 2011

Excess Vitamin D harms the heart - Study

Vitamin D in excess may not be beneficial and may even harm the heart says a new study. Scientists have long known that low levels of the nutrient can hurt the heart, but new research shows that higher than normal levels can make it beat too fast and out of rhythm, a condition called atrial fibrillation. The study was presented at the annual meeting of the American Heart Association.

The study, which followed 132,000 patients at a Utah based medical center, found that the risk of newly developed atrial fibrillation jumped almost three-fold when blood levels of vitamin D were high.

Researchers explain that most people get at least some of their daily needs of vitamin D from sunlight. But in cold northern climates where there is lack of exposure to the sun, people are often encouraged to take supplements to boost levels of the nutrient to protect the bones and heart, said the study’s lead author, Dr. Jared Bunch, director of electrophysiology research at the Intermountain Medical Center in Murray, Utah. However, because everyone absorbs these supplements differently, blood levels need to be tested to make sure they’re in the safe range, Bunch explained.

High levels of vitamin D only occur when people take supplements, Bunch said. Because consumers assume supplements sold over the counter are safe, they may not realize the danger of taking too much vitamin D, he added. “People are looking toward therapies considered to be natural to treat a broad variety of disease states and as a means of prevention,” Bunch said. “We see patients who take a tremendous amount of vitamin supplements.”

He added that normal range for vitamin D was 41 to 80 nanograms per deciliter (ng/dl). Patients in the study were designated as having excessive vitamin D had had readings above 100 ng/dl. Additionally the recommended daily intake of vitamin D for people from 1 year to age 70 is 600 IUs, or international units a day, based on what is sufficient for bone health, according to the National Institutes of Health. Oily fish such as tuna or salmon are among the best sources of vitamin D from food.

Bunch advises people who have recently been diagnosed with atrial fibrillation and are taking vitamin D supplements to make sure their doctors check blood levels of the nutrient. He suspects that the effects of high vitamin D on heart rhythms are reversible. “If the levels are excessive, I would hope that when they’re cut back the arrhythmias would improve as well,” Bunch said.

Vitamin D protects the heart: Study

Yet another Danish study called the Danish Osteoporosis Prevention Study shows that low levels of vitamin D may put women at greater risk for heart attack and stroke. After analyzing 16 years of data on more than 2,000 healthy, postmenopausal white women aged 45 to 58, researchers found that the 788 women with a vitamin D deficiency had more risk factors for heart disease than 1,225 women with normal levels of the vitamin. The results were presented Tuesday at the American Heart Association annual meeting in Orlando, Fla.

Women with low vitamin D levels had higher levels of triglycerides; higher fasting glucose; a higher body mass index; and lower HDL “good” cholesterol. The researchers noted 47 percent of the women who were deficient in vitamin D were smokers compared to 38 percent of the women with normal vitamin D levels. About 15 percent of the women deficient in vitamin D either died or suffered heart failure, a heart attack or stroke during the study period compared to 10.2 percent of the women who did not have this deficiency.

“Healthy women with vitamin D insufficiency have a significantly increased risk of adverse cardiovascular outcome,” wrote the researchers, led by Louise Schierbeck of Hvidovre Hospital in Denmark.

There were two more studies that looked at the possible protective effects of Vitamin D on the heart. One study found that people who took 4,000 units of vitamin D daily for five days following a severe heart event had less inflammation afterward than patients who didn't take the supplement. A second study found that chest pain patients with low Vitamin D levels were more likely to die during the next two years than those with adequate levels of the nutrient.