Is Vitamin D Overhyped?

Credit: Photograph by Shana Novak

Higher energy levels. Faster muscle recovery. Less stress and better sleep. Lower risk of cancer, dementia, and even flu. And, of course, a stronger heart and bones. These are the claims we've seen in health stories in just the past year about the wonder benefits of vitamin D — a nutrient that believers contend is able cure or prevent just about anything that ails us.

And it seems America is convinced that it's not getting enough of it. Blood tests for vitamin D, which cost upwards of $50 a pop and are frequently not covered by insurance, increased 83-fold from 2000 to 2010. (That's the last available stat, though experts predict the number is now far higher.) Vitamin D checks are the fifth most common lab test among older Americans, just below cholesterol screenings and above PSA tests. Meanwhile, sales of vitamin D supplements have shot up 700 percent since 2007, according to Nutrition Business Journal.

But does the stuff really deliver?

Alas, as with most things health-related, if it sounds too good to be true, it probably is. A chorus of top cardiologists and researchers are saying it's time for a reality check on vitamin D. Yes, our bodies need it — namely to help absorb calcium to keep our bones and hearts healthy — but far fewer of us are deficient than we've been led to believe. According to Dr. Erin Michos, a cardiologist and top vitamin D researcher at Johns Hopkins University, only some 30 percent of Americans have insufficient vitamin D, which means blood levels below 20 nanograms per milliliter (20 ng/ml). Fewer people still are actually deficient in the vitamin: about 8 percent, according to Michos. What's more, "the majority of people who are not taking vitamin D supplements probably still have levels in the low 20s," says Dr. Tod Cooperman, president of supplement research and testing firm ConsumerLab.com. In other words, most of us are doing just fine.

This hasn't stopped some physicians from pushing megadoses of vitamin D — up to 10,000 IU a day — claiming that more of the vitamin can only improve health. An onslaught of news reports has also cast vitamin D as a panacea. "In the past 10 years, there has been an explosion of research linking vitamin D deficiency to dementia, autoimmune diseases, cancer, you name it," says Michos. These studies — and the clickbait headlines that often promote them — depict vitamin D as both prevention and cure, something no nutrient could ever be.

The truth is, no study has indicated that if you get more vitamin D, you'll reverse health problems or prevent illness. Rather, "low vitamin D levels may be just a marker of a person getting too little outdoor physical activity, poor nutrition, or having poor overall health," says Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital. Popping a supplement isn't going to change any of that.

Bottom Line: There's nothing wrong with taking a D supplement to guarantee you never have a deficiency. And if you're rarely outside midday or you live in a northern state — which raises the likelihood that you're not getting direct sunlight, the best source of vitamin D — then supplementing may be a wise idea. But megadosing for otherwise healthy people, Cooperman insists, is unnecessary and dangerous. "Any more than 2,000 IU a day will push your blood level above 39 ng/ml, and then you start developing problems." Those include nausea, memory loss, kidney issues, and, strangely, brittle bones (proof that too little or too much of a nutrient can lead to the same problem). For most, a daily capsule equivalent to 600 IU will help you reach or stay at 20 ng/ml. And taking it means that you don't need to get your vitamin D levels checked. The supplement ensures your body has all of the nutrient it needs.