"I'm cautiously optimistic," says Dr. Amit Khera, Director of the Preventive Cardiology Program at University of Texas-Southwestern Medical Center and chairman of the American Heart Association's State Advocacy Committee. Some studies indicate that people with higher levels of vitamin D have a lower risk of heart disease and stroke, along with fewer risk factors such as high blood pressure and diabetes.

Now that could mean that vitamin D is just "keeping company" with other factors that lead to healthier hearts, Khera notes. But it makes sense biologically to him because the liners to the arteries have vitamin D receptors.

"It may be interacting with the arteries to make them healthy. I do think it's quite plausible that normalizing vitamin D may help lower heart disease risk. The evidence is not definitive, but it is pretty suggestive."

Khera says he hesitates to jump to conclusions after feeling "burned" with previous promises of vitamin E and hormone replacement therapy.

About 25 to 50 percent of the population has some degree of vitamin D deficiency, he says. He recommends speaking to your physician about whether you need to take vitamin D and the appropriate dose depending on your blood levels, age, and risks.

Although there are generally few side effects, he cautions that very large amounts can lead to excessive calcium levels, which could result in kidney stones, confusion, and lead to various aches and pains.

Vitamin D is produced through the skin by exposure to sunlight. With people spending less time in the sun and using sunscreens when they are outside, they need to get more of their vitamin D through supplements or a diet of fatty fish, eggs and fortified milk, he says.

In addition, obesity can lower vitamin D levels, with fat tissue preventing the vitamin from circulating in the blood.

"I think we have to be a little cautious about overdoing it," he says. "It's not some miracle. But the cost is minimal and there's not a lot of toxicity. And if the evidence continues to accumulate that vitamin D plays a role in heart health, we may become more aggressive about prescribing it to our patients."