Vitamin D

What is vitamin D?

Vitamin D is a nutrient that helps build strong bones and teeth. Vitamin D helps your body use and absorb calcium, which is also important for good bone health. If you have low levels of vitamin D, you may have a higher risk for bone disease (osteoporosis) and broken bones.

How much vitamin D do I need?

When the sun's UV-B rays hit the skin, skin cells make vitamin D. However, your body may not be making enough vitamin D. Many factors affect how much more vitamin D you need to get from food or supplements to keep a healthy blood level. These factors include:

• the color of your skin
• how strong the sun is where you live
• the season of the year
• how much time you spend outside
• how much you use sunscreen or cover up with clothing
• your age
• your diet
• your health conditions and risk factors

The current US daily recommendations for vitamin D are:

Age                      Vitamin D/Day
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Birth to 1 year                400 IU
1 year to 70 years             600 IU
Over 70 years                  800 IU
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* IU = international units

There is ongoing debate about the risks and benefits of higher doses of vitamin D. A number of studies suggest that higher doses might help treat and prevent serious diseases. More research needs to be done in this area.

Some experts recommend tests of your vitamin D blood level when you have a routine physical exam to see if you are getting enough vitamin D. However, this may not become a routine test until there are more studies that show that treatment of low levels of vitamin D can prevent some diseases.

What causes low levels of vitamin D?

You are more likely to not have enough vitamin D if:

• You have darker skin.
• You are older. As our bodies age, we don’t make as much vitamin D from sunshine
• You don’t drink milk.
• You rarely go outside. For example, you may be homebound.
• You are very overweight.
• Your body doesn’t absorb fat well. This may be because you have liver disease, Crohn's disease, or celiac disease. Not absorbing fat well can also be a problem if you have had gastric bypass surgery.

Children who don’t get enough vitamin D may be at risk for rickets. Rickets is a softening of the bones that can lead to broken or deformed bones.

How can I get more vitamin D?

To get more vitamin D:

• Eat more salmon (canned or fresh), mackerel, canned tuna or sardines. Each serving has 200 to 360 IU of vitamin D. Some varieties of salmon, such as sockeye, have over 750 IU. Liver and egg yolk also are also good sources. Sunlight is another source of vitamin D.
• Drink more vitamin-D fortified low-fat milk or orange juice. One cup has about 100 IU of vitamin D. If you aren't crazy about drinking plain milk, try low-fat chocolate milk. Soups and puddings made with milk provide vitamin D, too. Some brands of cheese, yogurt, juice, and margarine also have added vitamin D. Check food labels for nutrient information.
• Get a little bit of sun outdoors with no sunscreen most days in the late spring and summer. Spending some time in the sun is an efficient way to get vitamin D. (When you're indoors, sunlight on your skin coming through window glass is not strong enough to make vitamin D.) However, some experts don’t recommend being in the sun without sunscreen because of the skin cancer risk. It’s also hard to know how much you need, because different people’s bodies make different amounts of vitamin D from sunlight. Don’t stay exposed long enough to get sunburned. People with dark skin need more sun to get the same result. The more skin you expose, the less time you need in the sun. So if you’re in shorts and a sleeveless shirt or a bathing suit, you can cut the time down. Double your time in the sun on cloudy days. Talk to your healthcare provider about your risk for skin cancer.
• Take a multivitamin. Pick a formula that has 100% of the vitamin D recommended for your age.
• Take a vitamin D supplement. Don’t take more than the recommended amount for your age unless your healthcare provider advises taking more. Your body will absorb vitamin D best if you take it with a meal. You can buy calcium supplements that include vitamin D. If you can get enough vitamin D in your diet, you don’t need to take vitamin D supplements. Ask your healthcare provider or dietitian if you should take a vitamin D supplement.

Can I get too much vitamin D?

You cannot get too much vitamin D from sunshine. And unless you're taking lots of cod liver oil, you don’t have to worry about getting too much from food. However, you can get too much from supplements. Too much vitamin D can cause digestive upsets and calcium deposits in the kidneys and blood vessels.

In the US the current government safe upper limit for vitamin D supplements is 4,000 IU (100 micrograms) for anyone older than 9 years. The limit for children younger than this is lower and depends on the child’s age.

For more information about healthy eating, call the American Dietetic Association at 1-800-366-1655, or visit their Web site at http://www.eatright.org.