Why You Need More Vitamin D

A few years ago, vitamin D was nothing more than calcium's wingman, a secondary nutrient that helped the bone-building mineral make its move from the belly to the bloodstream and eventually plant itself in the skeleton. Well, no offense to C, but new research suggests that vitamin D may be one of the best vitamins of all for your body. The lab guys have uncovered up to 2,000 different genes—roughly one-sixth of the human genome—that are regulated by the nutrient. That means almost everything your body does relies on it.

"It affects cell death and proliferation, insulin production, and even the immune system," says Michael F. Holick, Ph.D., M.D., director of the vitamin D, skin, and bone research laboratory at the Boston University Medical Center.

Translation: Low vitamin D will result in your body working far below its potential. And you're probably not getting anywhere near the right amount. Here's why you'll be hearing a lot more about it and how you can score what you need to avoid a vitaimin D deficiency and make your body function at its absolute max.

Nutrition's New MVP
What's most remarkable about vitamin D is the sheer number of health issues it's been linked to. In the past few years, studies have shown that a lack of the vitamin may be the primary culprit in depression, heart disease, pregnancy problems, birth defects, skin and other cancers, and multiple sclerosis.

Even if you don't suffer from any of these conditions, getting more D may still be what the doctor ordered. "Many of my patients report a dramatic improvement in their feeling of overall well-being after they increase their vitamin D levels," Holick says. And a number of experts, including those from the Harvard School of Public Health, have urged the government to raise its recommended daily amount of vitamin D for adults from 200 IU to at least 1,000 IU, possibly more.

Why We're D-ficient
According to a report in the Archives of Internal Medicine, experts believe that up to 77 percent of Americans are vitamin D deficient (defined as having blood levels of less than 30 nanograms per milliliter).

So why do we come up so short, especially since vitamin D is one of the few vitamins our bodies can actually make? Sunlight converts a cholesterol-like substance naturally found in the skin into D. Problem is, thanks to UV rays and skin cancer, soaking up sun to make more D would do you more harm than good. For your skin to make enough, you'd need direct midday summer sunlight on a huge portion of your body for 15 minutes a day—risking serious sun damage.

Besides, it wouldn't help much, Holick says. If you live north of Atlanta, it's impossible to get enough D from sunlight between October and March, no matter how exposed you are. And it's tougher for people of color to make D—the melanin in dark skin decreases vitamin D production by up to 90 percent.

To make matters worse, D is missing from the food we eat, says Beth Kitchin, M.S., R.D., assistant professor of nutrition sciences and patient educator in the Osteoporosis Treatment and Prevention Clinic at the University of Alabama at Birmingham. Only certain kinds of fish and fortified dairy have enough D to brag about, and it would be hard to consume enough of both in one day to get 1,000-plus IU.

Easy to Swallow
There's a simple way to get your D up without baking in the sun. It's not often that nutrition experts say it's better to get a vitamin from a pill than from food, but D is an exception. "In this case, supplements are the easiest, cheapest, and safest way to make sure you're covered," says Laura Armas, M.D., assistant professor of endocrinology and a researcher in the Osteoporosis Research Center at Creighton University in Omaha, Nebraska.

Can you OD on it? It's possible, but extremely unlikely. Vitamin D is fat-soluble, which means you won't pee out the excess as you would a water-soluble vitamin like C. This used to worry experts, who thought that D could easily build up to toxic levels. But further study has found that our bodies can handle a lot more than previously understood. "You'd have to ingest 10,000 IU every day for six months before you'd even begin to approach problem levels," Holick says. It's much more likely you're not getting enough, he says. A few ways to get your D intake up to par:

• Take a daily multivitamin or a vitamin D supplement that provides at least 1,000 IU. In addition, Holick says, drink two glasses of skim milk per day.

• When buying supplements or fortified foods, make sure the label reads "D3." This is the same type the skin makes, but some companies still use D2, a plant-based form of the vitamin that the body doesn't metabolize as easily.

• Get your blood levels measured, especially if you have a family history of heart disease, cancer, or depression. If you are extremely low, your doctor might recommend higher doses of D.