Vitamin D.

It's called the "sunshine vitamin"— and it's crucial to many aspects of your good health. Here's how to make sure you get enough.

If you’re a runner, you’re probably acquainted with the occasional post-workout or day-after-a-race muscle pain. Deborah Compton, a Newark, Del., resident and a runner for decades, was, too. But when she started to feel chronic aches in her legs, she became concerned. “It was hard to lift my legs. I was kind of dragging around,” she says. Her doctor ran some tests and gave her a clean bill of health, but Compton, then 58, was sure something wasn’t right.

Finally, her pharmacist heard about her symptoms and suggested Compton take a vitamin D blood test — called a 25-hydroxy vitamin D test. It turned out that her vitamin D level wasn’t just low — it was at rock-bottom. The Institute of Medicine (IOM) considers the deficiency zone 20 nanograms per milliliter. Compton’s was about 5 ng/mL.

The National Center for Health Statistics says more than one-third of Americans are vitamin D deficient, and other research suggests that figure could be as high as 50%.

Sure enough, within a month of starting a daily vitamin D supplement of 2,000 international units (IUs), Compton says, the pain in her legs ceased. Her sleep, which had been troubled as well, evened out again. Five years after her diagnosis, Compton still takes her supplements religiously and has had no further problems.

Why vitamin D is crucial

It may seem as though vitamin D is everywhere these days: Food packages boast it’s inside, supplements jam shelves and health websites wax over its benefits. There are reasons it’s so buzz-worthy: Vitamin D helps control calcium and phosphorus levels in the body, and it plays a role in cell growth, immunity and reducing inflammation. It’s well established that vitamin D deficiency in children can lead to rickets, a bone-thinning condition that can cause deformities. In adults, it can cause osteomalacia — muscle and bone weakness. And new research suggests low D is also linked to cancer, autoimmune problems and heart disease.

Where to get your D

The sun is an excellent source of vitamin D. It’s challenging to obtain vitamin D from food alone, says Elisabetta Politi, nutrition director at the Duke Diet and Fitness Center. Fatty fish such as salmon and fortified dairy products, juices and cereals are good sources, but you’d have to eat them every day to get your daily requirement. Plus, “mushrooms are one of the only D-rich vegetables,” Politi says.

How to get Vitamin D from the Sun

• 5-10 minutes of mid-day (10 am - 3 pm) mid-year sun-light on arms and legs provides about 3000 IUs of D to a light-skinned Caucasian.
• Getting this amount 2-3 times weekly is sufficient for most, but those with a big deficiency may need it.
• Going shirtless delivers more Vitamin D, so less time under the sun is needed.
• Obese and dark-skinned individuals require more sunshine.
• Where you live and your age, skin color and obesity all have an impact a person's Vitamin D exposure from the sun.

Supplements may be an option, especially if you work indoors, live in a Northern clime or have a family history of skin cancer. People with more pigmented skin take longer to absorb sunlight, as do those who have diabetes or take anticonvulsive drugs.

That said, experts have yet to determine just how effective supplements are in combating many of the worrisome conditions caused by a D deficiency. Kevin Fiscella, professor of family and community and preventive medicine at the University of Rochester in New York, says large clinical trials are needed to learn more.

JoAnn Manson, chief of preventive medicine at Harvard’s Brigham and Women’s Hospital, hopes to address those questions. Last year, she launched the VITAL study of 20,000 men and women, which is examining whether daily dietary supplements of vitamin D3 or omega-3 fatty acids reduce the risk of cancer, heart disease and stroke. Half of Manson’s participants will take 2,000 IUs of vitamin D3 a day, and the rest will be given a placebo. All will be encouraged to follow a diet adequate in vitamin D, and results should be out in about five years, says Manson, who is still seeking participants (vitalstudy.org).

How much do you really need?

Until her study is complete, Manson recommends following the Institute of Medicine’s guidelines that adults up to age 70 should get 600 IUs of vitamin D a day, and those over 70 should get 800 IUs a day.

But other experts say the guidelines hover on the low side. Before you load up on supplements or fish, talk to your doctor. Doses that are too high can lead to kidney stones, warns Carl Lavie, medical director of cardiac rehabilitation and prevention at New Orleans’ John Ochsner Heart and Vascular Institute.

And while the 25-hydroxy vitamin D test can be ordered by your doctor, it’s not necessary unless you have other health risks such as diabetes or heart disease, says Roger Blumenthal, director of the Johns Hopkins Ciccarone Preventive Cardiology Center. “Until we see the results of the VITAL study and other trials,” Blumenthal says, “I think most clinicians would say if you have very low D levels, we’ll give you supplements, but whether that will help is far from certain.” The bottom line: Follow as balanced a diet as you can, get outside a little bit every day, and if you’re feeling out of sync, don’t forget to ask your doc about D.

© USA Weekend | By Mary Brophy Marcus