What Is Vitamin D?

Reviewed by Jill Kohn, MS, RDN, LDN
Sunlight and Milk - What is Vitamin D?

According to the 2015-2020 Dietary Guidelines for Americans, vitamin D is a nutrient of public health concern. In May 2016, the Food and Drug Administration announced food manufacturers are required to include vitamin D content on the Nutrition Facts label.

Vitamin D is a nutrient needed for health and to maintain strong bones. Vitamin D aids in the absorption of calcium and phosphorus in our bodies, helps bring calcium and phosphorus to our bones and teeth, and helps regulate how much calcium remains in our blood. Together with calcium, vitamin D helps protect against the loss of bone mass.

Vitamin D's importance does not end there. It is also helps muscles function and allows the brain and body to communicate through nerves. And the immune system needs vitamin D to fight off invading bacteria and viruses. There three ways to get vitamin D: the sun, your diet or supplements.

Vitamin D from the Sun

Known as the "sunshine vitamin," your body converts sunlight into vitamin D after it hits unprotected skin. However, be careful to avoid extended exposure to sunlight without sunscreen.

Vitamin D from Diet

Very few foods naturally have vitamin D. Fatty fish such as salmon and tuna are among the best sources of vitamin D. Beef liver, cheese and egg yolk provide small amounts. Mushrooms also contain this vitamin if grown under UV lights.

Fortified foods provide most of the vitamin D in our diets. Most milk and cereals are fortified with vitamin D, as well as some types of orange juice, yogurt, cheese and soy beverages. Check the Nutrition Facts label for vitamin D content.

Vitamin D from Supplements

Some individuals may need extra vitamin D, such as seniors; breast-fed infants; people with dark skin; those with certain medical conditions including liver disease, cystic fibrosis, celiac disease and Crohn's disease; and those who are obese or have had gastric bypass surgery. Always check with your health care provider before taking a vitamin D supplement.

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