I find that my patients are very confused about vitamin D supplementation. They routinely ask me: Should I take vitamin D for my heart health? To stiffen up the bones? Or only if blood work shows low vitamin D levels? And, most importantly, are vitamin D supplements safe?
To get the answers to these questions, I figured I would go directly to an expert—Dr. Erin Michos, an assistant professor of cardiology at Johns Hopkins—who receives grant money from the National Institutes of Health (NIH) to help provide the scientific data underpinning our understanding of vitamin D’s benefits. Here are her answers to my questions.
Dr. Blaha: Hi Erin, glad you could join me on my Yahoo! blog. What does the latest research say about vitamin D and heart health?
Dr. Michos: Recent studies have linked vitamin-D deficiency with an increased risk of high blood pressure, diabetes, and cardiovascular diseases such as heart attacks, strokes, and congestive heart failure. So far, these studies have been mostly observational, along with supportive research in animals. But, right now, there are no large clinical trials to provide solid evidence that vitamin D supplementation for those who are deficient actually lowers the risk of cardiovascular diseases. The important clinical trials we need, however, are now underway.
Dr. Blaha: Who should get their blood tested for vitamin D deficiency?
Dr. Michos: I recommend that many of my at-risk adult cardiology patients get tested for vitamin D deficiency. Blood levels of vitamin D can be measured with a simple blood test, called 25-hydroxyvitamin D. Although not the active vitamin D hormone, 25-hydroxyvitamin D levels are the best indicators of how much vitamin D is stored in the body.
Dr. Blaha: Do you ever prescribe vitamin D supplementation?
Dr. Michos: If patients are deficient, I recommend supplementation. While many experts recommend that levels should be above 30 nanograms (billionths of a gram) per milliliter of blood (ng/ml), the 2010 Institute of Medicine report declares that a level greater than 20 ng/ml is probably adequate. At this time, we know that vitamin D deficiency is easy to screen for, and treatment is readily available. But whether treating vitamin D deficiency can prevent heart disease remains unknown—I therefore stress that vitamin D supplementation, when it’s taken exclusively for cardiovascular disease prevention, cannot be strongly recommended right now.
Dr. Blaha: How about for the bones?
Dr. Michos: At the very least, we do know vitamin D helps patients build strong bones, so that is another reason to screen for and treat deficiency.
Dr. Blaha: What is the best source of vitamin D?
Dr. Michos: It can be very challenging to get enough vitamin D in the foods we eat. With a little help from the sun, however, the body can make its own vitamin D. In the summer months, less than half an hour of sunlight a day on the bare limbs allows the body to produce all the vitamin D it needs—but readers mustn’t take this as a recommendation to spend many hours in the sun without sunscreen protection!
And—another caveat—please don’t gobble down large amounts of supplements without consulting your doctor. Too many vitamin D supplements can lead to toxicity (vitamin D poisoning), which is linked to dehydration, kidney stones, and hardening of the arteries! First try modest sunlight exposure, eating foods that contain vitamin D (such as oily fish like salmon and fortified low-fat dairy products), regular physical activity, and maintaining an optimal body weight.