Vitamin D has been called the new "wonder vitamin." Doctors are learning more and more about its role in good health and the prevention of diseases. Unfortunately, though, most teens don't get enough.

Why Do I Need It?

Vitamin D plays a part in the bone-building process by helping the body to absorb calcium. If someone doesn't get enough, it could affect the body's ability to build and maintain strong bones and teeth.

It's not just about bones, though. Vitamin D is needed for a healthy immune system — helping the body to fight off infections and prevent the development of autoimmune diseases like rheumatoid arthritis. Research done in adults suggests that getting enough vitamin D can help lower the chances of developing heart disease, certain cancers, and other serious diseases like diabetes.

Why Don't People Get Enough?

There are several reasons why people don't get enough vitamin D:

• Less exposure to UV rays. Vitamin D is sometimes called the "sunshine" vitamin. When the sun's ultraviolet rays penetrate bare skin, it sets off a process in the body that produces vitamin D. Since lots of us spend more time on computers and game consoles, we're not outdoors as much as we once were. And, when we do spend time in the sun, more of us are making the wise decision to use sunscreen to block the UV rays that cause sun damage and cancer. Where we live makes a difference, too: If you live in northern U.S. and Canada, it's possible you're not getting the UV exposure required for your body to make enough vitamin D.
• Dark skin. The melanin (the pigment that gives skin its color) in darker skin protects against sun damage, but it can also block the sun needed to produce vitamin D.
• Certain health conditions. Some health conditions, like cystic fibrosis or inflammatory bowel disease, affect how well the body absorbs nutrients, including vitamin D. And, because vitamin D is a fat soluble vitamin that gets stored in the body's fat cells, obesity increases a person's risk for vitamin D deficiency.
• Lower consumption of D-rich foods. Experts recommend eating vitamin D-rich food as the best way to ensure you get enough vitamin D. But many of the best foods — like fatty fish and oil — are not the most popular. These days, most milk is "fortified" with added vitamin D. But lots of times teens often aren't drinking enough milk to get the recommended daily amount.

How Much Vitamin D Do I Need?

The American Academy of Pediatrics recommends that teens get 600 IU (international units) of vitamin D per day. Ask your doctor about taking a daily multivitamin or vitamin D-only preparation that contains the 600 IU of vitamin D you need.

You may need even more than 600 IU if you have darker skin, live in areas with limited sunshine, have a condition that affects how well your body absorbs nutrients, or if tests show you have low vitamin D levels. Check with your doctor before taking higher doses, though. Vitamin D is a fat-soluble vitamin, meaning it gets stored in the body. In rare cases extremely large doses could build up to dangerous levels.

Doctors recommend an upper limit of 2000 IU of vitamin D per day for teens. Most people who eat foods rich in vitamin D, who get normal sun exposure, and who take a 600 IU supplement will not get toxic buildup of vitamin D in their bodies. Problems with vitamin D toxicity happen when people take supplements with megadoses of the vitamin or lots of different supplements containing the vitamin. As always, your doctor is the best advisor of what works for you!

Ways to Work More Vitamin D Into Your Diet

As with all vitamins, it's best to get our D through the foods we eat.

The best sources of vitamin D are:

• fatty fishes and fish oils, such as salmon, mackerel, and cod liver oil
• eggs
• vitamin D-fortified milk and other dairy products

Lots of other foods are fortified with vitamin D, including orange juice, soy milk, cereals, and bread. Read the nutrition facts label to see how much vitamin D is in each serving.

So what should you do about D? Try adding more D-rich foods to your meals and take a supplement that contains 600 IU. If you think you're not getting enough after that, talk to your doctor.

Reviewed by: Mary L. Gavin, MD
Date reviewed: April 2010