Vitamin D and your health
You may think you're eating a healthy diet that fulfills most requirements for good nutrition. But you could—without knowing it—come up short on an essential vitamin.
That vitamin is vitamin D, which plays a critical role in the development and maintenance of healthy bones and teeth. Without it, the body can't absorb the calcium and phosphorus it needs to build and preserve bones. And—because bone formation and maintenance occurs throughout life—you never outgrow your need for vitamin D.
How does vitamin D help?
In sufficient amounts, vitamin D can help prevent diseases such as rickets (deformed bones) in children, osteomalacia (soft bones) and osteoporosis (brittle bones) in adults, and (along with calcium) tooth loss in the elderly.
There's evidence that vitamin D can help maintain a healthy immune system. And some research suggests that it might reduce the risk for certain cancers.
How much vitamin D do I need?
The Health and Medicine Division of the National Academies of Sciences, Engineering, and Medicine recommends the following daily amounts of vitamin D:
- 400 international units (IUs) for infants from birth to 12 months.
- 600 IUs for children and adults ages 1 to 70, including pregnant and lactating women.
- 800 IUs for people ages 71 and older.
The current upper limit established by the Health and Medicine Division is 1,000 IUs from birth to 6 months; 1,500 IUs for ages 6 to 12 months; 2,500 IUs for ages 1 to 3 years; 3,000 IUs for ages 4 to 8 years; and 4,000 IUs for everyone else.
Taking too much vitamin D could cause nausea, vomiting, poor appetite, constipation, weakness, weight loss and changes in mental status, such as confusion. The most common way to get an overdose is from taking high doses of the vitamin in supplements, according to the National Institutes of Health (NIH).
Where can I get my vitamin D?
Vitamin D is available in a form your body can use from three sources:
Diet. Foods rich in vitamin D are limited. Fatty fish such as salmon, mackerel and tuna contain from 250 to 600 IUs per serving.
Some foods, such as milk, have vitamin D added to them. One cup of fortified milk contains about 100 IUs. Other dairy products are not usually fortified and contain only small amounts of the vitamin, according to the NIH.
Orange juice and some cereals and breads are sometimes fortified with vitamin D. Check product labels to see how much they contain.
Sunshine. Your body can make vitamin D if your bare skin is exposed to ultraviolet (UVA and UVB) rays from the sun. But these rays can cause skin cancer. And not everyone agrees on how much sun is safe.
It is possible to get vitamin D with only limited time in the sun. According to some researchers, five to 30 minutes of direct sun exposure (no sunscreen) between 10 a.m. and 3 p.m. at least twice a week on the arms, legs or back is usually enough.
The American Academy of Dermatology takes a more cautious position. The group recommends using sunscreen anytime you are exposed to sunlight.
The American Academy of Pediatrics advises that children wear sunscreen when they are in the sun. That means babies and young children need to get their vitamin D elsewhere to protect against rickets.
How much sun a person needs may depend on age, diet, skin color and where he or she lives. Your doctor can help you decide how much sun is safe for you.
Vitamin supplements. If you are considering supplements for yourself or a child, first talk to your doctor or a registered dietitian. Most multivitamins and some calcium supplements contain vitamin D. Check the label to find out how much is in them. That will help you get enough, but not too much.
Who needs supplements?
Some people are especially at risk for a vitamin D deficiency. For example, breastfed babies need a liquid supplement because, even though it's considered ideal for infants in every other way, breast milk does not contain a sufficient amount of vitamin D. Formula-fed infants usually get recommended amounts of the vitamin because federal law requires a certain amount of vitamin D in infant formulas, the NIH reports.
According to the NIH, supplements also should be considered for people who:
- Are obese.
- Are older. As people age, their skin uses vitamin D less efficiently, and the kidneys—which convert the vitamin to a form the body can use—may not be able to do their job.
- Live in an area of heavy air pollution. Pollution filters out the sun's UVB rays.
- Don't or can't eat fish or dairy products (for example, vegans and people who are lactose-intolerant).
- Have dark skin. Darker skin doesn't produce as much vitamin D as light skin in response to sunlight.
- Can't absorb fat. Because vitamin D is a fat-soluble vitamin, it requires some dietary fat for absorption into the body. People may have trouble absorbing fat if they have Crohn's disease, cystic fibrosis, celiac or liver disease, or if they have had all or part of their stomach or intestines removed.
- Spend most of their time indoors. Even if a person sits next to a sunny window, the sun's UVB rays can't penetrate through the glass.
- Regularly take corticosteroids. These medicines may impair the body's ability to use vitamin D.
How would I recognize a deficiency?
Symptoms that could indicate a vitamin D deficiency are dull, aching pain that affects many parts of the body, including bony areas such as the ribs and breastbone; weakness; and falls (in older people). If your doctor suspects a deficiency, he or she may recommend a blood test.