What is Vitamin D?
As nutrients go, vitamin D is in a class by itself. That's because vitamin D is actually a hormone that the body produces in response to direct exposure to Ultraviolet B (UVB) rays from the sun. Vitamin D is classified as a fat-soluble vitamin, which means that both the vitamin D your body produces and that which you consume in your diet are stored in fat tissue for later use.
Benefits of Vitamin D
Vitamin D helps maximize your body's ability to absorb calcium you take in from foods and supplements. It also regulates calcium's movement into, and out of, your bones in order to maintain calcium levels throughout the body. Without enough vitamin D circulating in your bloodstream, absorption of adequate calcium is difficult.
That's not all Vitamin D does. Recent science suggests that vitamin D influences cell growth, immune function, and may help support nervous system functions. One thing is for certain: adequate vitamin D is essential to maintain strong bones.
How Much vitamin D do I Need?
According to the Institute of Medicine (IOM), the amount of vitamin D recommended daily depends on your age. From age one to 70, get 600 IU daily; people over the age of 70 should get 800 IU per day. Vitamin D requirements do not increase during pregnancy and breastfeeding.
Where Do I Get Vitamin D?
You can get vitamin D from direct sun exposure, certain foods, and supplements.
Strong sunlight triggers vitamin D production in your skin. Your liver, kidneys, and cells throughout the body complete the conversion of vitamin D's most active form, 1,25-vitamin D3.
In theory, you should be able to make all the vitamin D you need by getting adequate sunlight. In reality, many people do not produce the required vitamin D or get adequate amounts from food and dietary supplements. According to the 2010 Dietary Guidelines for Americans, most children and adults consistently come up short for vitamin D.
What factors affect my vitamin D status?
You may not be getting enough vitamin D if you:
Sources of vitamin D in food
For such an important nutrient, few foods are natural sources of vitamin D. Some commonly consumed foods, including milk and orange juice, are fortified with vitamin D. Here are some foods that contain vitamin D:
|Food||IUs per serving|
|Source: Adapted from Dietary Supplement Fact Sheet: Vitamin D.|
|Salmon (sockeye), cooked, 3 ounces||447|
|Mackerel, cooked, 3 ounces||388|
|Tuna, canned in water, drained, 3 ounces||154|
|Milk, any fat level, vitamin D-fortified, 1 cup||115-124|
|Orange juice, vitamin D-fortified (check labels for exact amounts)||100|
|Yougurt, fortified, 6 ounces||80|
|Egg yolk, 1 large||41|
Since relatively few commonly consumed foods supply vitamin D, it's often difficult to get the vitamin D you need from diet alone. For example, if you're under 70 years of age, you'd need to consume one of the following to meet your recommended levels of vitamin D:
It's no wonder many people (especially those of us who don't live in California or Florida!) can come up short when it comes to vitamin D.
Luckily, dietary supplements can help fill the gap to help you reach your daily goals.
A note from the experts:
Some experts in the field of vitamin D research believe that higher amounts of vitamin D than those recommended by the IOM may be necessary for maintaining higher levels of vitamin D in the blood stream to support bone and general health.
To find out how much vitamin D is right for you, see your doctor and ask him or her to check your serum levels of 25-hydroxyvitamin D.
Vitamin D supplements have the potential to interact with several common medications and certain medications may impact your body's vitamin D status. Ask your doctor about the potential for these interactions.