The Benefits of Vitamin D
One of the biggest roles vitamin D plays in your body is helping your bones grow, says Shanna Levine, M.D., an assistant professor of medicine at the Icahn School of Medicine at Mount Sinai. “It has also been found to play a role in cell growth, reduction of inflammation, and neuromuscular function,” she says.
But that’s not where the benefits end, says Michael F. Holick, M.D., Ph.D., author of The Vitamin D Solution. Research has linked sufficient vitamin D levels to everything from increased fertility and a reduced risk of breast cancer to fewer respiratory infections and even reduced severity in diseases like MS, he says.
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How to Tell if You Might Be D-Deficient
Before you pop a supplement, you first would want to know if you even eed one, right? Well, between 30 and 60 percent of the U.S. population could be deficient in vitamin D, says Levine. In particular, many people living in northern climates suffer from low levels of the vitamin, adds Donald Levy, M.D., medical director of the Osher Clinical Center for Complementary and Integrative Medical Therapies at Brigham and Women’s Hospital in Boston.
Your body creates vitamin D when exposed to UVB rays from the sun—but if you live north of Atlanta, due to the way the sun is positioned, that only happens between April and October, says Holick.
Certain people are more susceptible to deficiencies, too. If you have dark skin, your body doesn’t synthesize as much of the vitamin, putting you at risk for low levels, says Levine.
Obese people can also be two or three times more likely to suffer from deficiencies, as vitamin D is fat soluble, says Holick. Pregnant women are at high risk as well. Babies put increased demands on your body, so you may need to consume more of the vitamin to ensure you’re getting enough.
But you won’t really know that you’re deficient unless you get tested—and vitamin D screenings aren’t exactly standard. That said, if you think your levels are lagging (being super drained and experiencing aches and pains are both signs you could be in need of D), it’s reasonable to consider the blood test. (Just go in the winter, when your levels are most likely to be low, says Levine.) If you are indeed deficient, your doc may prescribe 1,000 to 2,000 International Units (IUs) a day or more, depending on your levels, she says.
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So, Should You Actually Take a Supplement?
In the scientific community, whether or not we all need a daily supplement of D is a controversial question that depends on a lot of different factors. Research supports both sides—as do experts. Holick says, “absolutely, positively yes,” we all should all supplement. The National Institutes of Health recommends the average person get 600 IUs a day. But if you’re a big seafood fan, get plenty of sunshine, and don’t have any symptoms, it’s likely not necessary, says Levine.
Still, some vitamin D research suggests that five to 30 minutes of sun exposure twice a week can be enough for vitamin D to synthesize. You can also stock up on D-rich foods like swordfish, salmon, OJ fortified with vitamin D, milk, yogurt, and cod liver oil (one tablespoon has 1,360 IU, according to the USDA!).
The bottom line: Listen to your body and consider all of the factors that impact your D levels to begin with—including your location, skin type, sun exposure, and diet. If you’re really unsure, or if you’re pregnant or have symptoms that indicate a deficiency, talk to your doctor. People who are deficient should supplement, but knowing your levels (and addressing any issues head-on) is always better than playing a guessing game when it comes to your health.