Vitamin D It is well known to be important for bone news block. It has also been studied for its possible link to a lower risk of a wide variety of conditions. But even though you can get vitamin D from food, supplements, or spending time in the sun, many people don’t get enough.
Why? Maybe you’re not getting enough from your diet. Other things that affect your body’s ability to make vitamin D include the season, time of day, where you live, air pollution, cloud cover, sunscreen, exposed body parts, skin color and age. Dermatologists recommend using sunscreen and get vitamin D from food and supplements instead of risking the sun’s harmful rays.
Role of vitamin D
Vitamin D is naturally present in some foods. But it is in many fortified foods.
Since 1930, virtually all cow’s milk in the US has been fortified with 100 IU of vitamin D per cup. Food manufacturers fortify other foods such as yogurt, cereals, and orange juice.
“vitamin D deficiency is associated with low bone mass and osteoporosisthat affects an estimated 10 million adults over the age of 50 in the United States,” says Atlanta rheumatologist Dr. Eduardo Baetti. He says that many of his patients, especially older and dark-skinned people, have low levels of vitamin D because the sun is not a reliable source.
How much vitamin D do you need?
The National Institutes of Health recommends that people get this daily amount of vitamin D:
- From birth to 12 months: 10 micrograms (mcg) or 400 international units (IU)
- From 1 to 70 years: 15 mcg (600 IU)
- Age 71 and older: 20 mcg (800 IU)
Older adults need more vitamin D because as they age, their skin doesn’t produce vitamin D efficiently, they spend less time outdoors, and they tend not to get enough vitamin D.
The best sources of vitamin D
The sun is an excellent source of vitamin D, but it’s hard to quantify how much vitamin D you get from sun exposure, and the risk of skin cancer may outweigh the benefits.
Food comes first, says dietitian Keli Hawthorne of Baylor College of Medicine. “supplements can fill in the gaps, but it’s always best to try to meet your nutritional needs with foods that contain fiber, phytonutrientsand much more,” he says.
Unless you enjoy a diet that includes fatty fish or fish liver oils, it can be difficult to get enough vitamin D naturally without eating fortified foods or taking a supplement. “The main dietary source of vitamin D comes from fortified dairy products, along with some yogurts and cereals,” says Hawthorne. Mushrooms, eggs, cheese, and beef liver contain small amounts.
How much is too much?
Because vitamin D is a fat-soluble vitamin, it can build up in the body. So it is possible to get too much of it.
The National Institutes of Health says these are the upper limits per day for vitamin D:
- Birth to 6 months: 25 mcg (1,000 IU)
- Babies 7 to 12 months: 38 mcg (1,500 IU)
- Children 1 to 3 years: 63 mcg (2,500 IU)
- Children 4 to 8 years old: 75 mcg (3,000 IU)
- Children 9 to 18 years: 100 mcg (4,000 IU)
- Adults 19 years and older: 100 mcg (4,000 IU)
- If you are pregnant or nursing: 100 mcg (4,000 IU)
“There is potential for harm if you take an overdose of supplements above 4,000 IU/day, but there’s no fear of sun overdose, because your skin acts as a regulatory system, allowing only the amount of vitamin D you need to be produced,” says Patsy Brannon, PhD, professor of Cornell University Nutritional Sciences who was part of an Institute of Medicine committee that reviewed the vitamin D recommendations.
Acceptable blood levels of vitamin D
Part of the confusion about whether or not you’re getting enough vitamin D may be the definition of the acceptable level of vitamin D in your blood, measured clinically as 25-hydroxyvitamin D [25(OH)D].
Using blood levels of vitamin D is the best estimate of adequacy that takes dietary intake and sunlight into account, although experts differ on what that level should be.
“The IOM committee used a blood level of 25(OH)D of at least 20 nanograms/ml to establish vitamin D recommendations because this level was shown to be adequate for a wide variety of indicators of bone news block,” says Brannon.
The Endocrine Society Practice Guidelines, as well as many laboratories and experts, recommend a minimum blood vitamin D level of 30 nanograms/mL as an acceptable level.