A growing number of studies point to vitamin D deficiency as a risk factor for heart attacks, congestive heart failure, peripheral arterial disease, strokes, and the conditions associated with cardiovascular disease, such as high blood pressure and diabetes.
Dr. Erin Michos, assistant professor of medicine at Johns Hopkins Hospital in the Division of Cardiology, has examined and contributed a great deal of data on vitamin D deficiency and the heart, including a study published in the Archives of Internal Medicine. She stops short, however, of stating that raising vitamin D levels lowers the risk of cardiovascular disease.
“Now that we have identified this risk factor for heart disease,” Dr. Michos says. “The question is, if you’re deficient and I give you vitamin D back, can I actually prevent a heart attack?”
Dr. Michos believes that question will be answered more conclusively by large clinical trials during the next five to eight years.
What is vitamin D?
Vitamin D acts as a hormone, regulating more than 200 genes throughout the body. It does an impressive amount of work. For example, vitamin D keeps abnormal cells from multiplying in breast and colon tissues; helps regulate blood pressure in the kidney; and helps regulate blood sugar levels in the pancreas.
Your body produces vitamin D on its own, particularly when you’re out in the sun. Because people are spending less time outdoors, and using more sunscreen when they are outdoors, there is a general deficiency among the entire American population.
There are other factors that lead to lower vitamin D levels, like your weight, skin, pigmentation, sex, age, and where you live.
Obesity is an important factor because fat cells absorb vitamin D and keep it from circulating throughout the bloodstream.
People with darker skin pigmentation have a built-in natural sunscreen called melanin, which keeps the skin from synthesising vitamin D.
Women have lower vitamin D levels than men for a few possible reasons: Women tend to have more body fat than men, they spend a bit more time indoors, and tend to wear hats and sunscreen more often than men.
Because several studies have connected low vitamin D levels with cardiovascular disease, this could be cause for women to pay special attention to screening.
Age also plays a role in vitamin D deficiency, because as people get older they absorb less vitamin D from their diet and produce less vitamin D in their skin. Also, their reduced activity gives them less opportunity to be outdoors.
According to Dr. Michos, geography also plays a part. If you live farther away from the equator, you aren’t exposed to enough ultraviolet light, so your body is unable to make vitamin D from November to February.
Maintaining vitamin D levels
Ask your doctor to check your vitamin D level. You’ll take a simple blood test called 25-hydroxyvitamin D. The measurement is nanograms per millilitre, and it’s generally recommended to keep your levels between 30 and 60 ng/ml.
Locally, Dr. Sook Yin, medical director of the Cayman Heart Fund, said she has started testing her patients’ vitamin D levels and has found about half are deficient in the vitamin.
Dr. Michos suggests that to maintain healthy levels most adults on average probably need 1,000 to 2,000 International Units a day. Though she adds that someone who lives in a sunny climate, like southern California or Cayman, and spends a fair amount of time in the sun might have healthy levels and not need supplements at all.
Conversely, women with levels well below 30 ng/ml might need a carefully monitored prescription of up to 50,000 IU per week for several weeks, followed by a lower over-the-counter dosage when vitamin levels are back to normal.
Although you can find vitamin D in fatty fish such as salmon, fortified orange juice, and milk, sunlight is the strongest natural source for vitamin D.
Dr. Michos explains that getting about 10 minutes of moderate summer sun exposure can supply you with 3,000 to 5,000 IU of vitamin D. You would have to drink approximately 30 glasses of milk to match that amount.
A direct link has yet to be formed between higher vitamin D levels and lower cardiovascular risk, but it’s important not to overlook other possible benefits.
“While we don’t know for sure whether treating with vitamin D can prevent a heart attack, I know at the very least vitamin D is good for the bones,” Dr. Michos said. “So I do recommend screening and treating, particularly because women tend to have more fractures and osteoporosis than men.”
We’re still a few years away from clinical trials that explore the possible link between taking vitamin D supplements to achieve higher vitamin D levels, and lower cardiovascular risk.
Dr. Erin D. Michos is an assistant professor of medicine at the Johns Hopkins Hospital.