To D or Not to D?


My (Valerie’s) Grandpa came to the United States from Norway, a country that is even farther north than Wisconsin! It is called “The Land of the Midnight Sun” because in June the sun doesn’t set. It is light, even at midnight!  They receive lots of sunshine in the summer, but the reverse happens in the winter. In December, it is dark the entire day. My grandpa had slightly bowed legs.  He said it was because they didn’t have milk to drink much of the time, but I’ll bet it was also due to a vitamin D deficiency from a lack of sunshine during half of the year.

Why do we need vitamin D?

We need vitamin D in order to absorb the calcium our bones and teeth need to be strong. If we don’t have enough vitamin D as a child, our legs can bow, we can have delayed tooth formation, deformities of the skull and ribcage, and decreased muscle strength—not to mention bone pain! As an adult, if we don’t have enough vitamin D, our bones can soften and bow or easily fracture. Vitamin D is also important for our immune system to work properly.

How much vitamin do we need?

Stage of Life

Vitamin D recommendation

Infants 400 IU/d
Ages 1-70 600 IU/d
Ages 71 and older 800 IU/d

Where can we get vitamin D?

There are 3 ways to get vitamin D.

First, we can get it from the sun. Our skin has the ability to convert the UV rays in sunshine into vitamin D. However, some things can decrease the production of vitamin D in our skin. Sunscreen, for example, can block the sun’s rays and thus, production of vitamin D.  Melatonin in our skin can also block the sun’s rays. Darker-skinned people have more melatonin, resulting in reduced vitamin D production. Smog, cloud cover, and clothing can also reduce the amount of UV rays that reach your skin. Did you know that from November to March in Wisconsin the sun is so filtered that it can’t even stimulate production of vitamin D in our skin?

Secondly, we can get Vitamin D from food. There are a few foods that are naturally high in vitamin D, like salmon, tuna, egg yolks, and beef liver. Most milks and some juices are now fortified with vitamin D. In order to meet the recommendation, an adult less than 70 years old would have to drink about 6 cups daily of milk or eat 4 oz of salmon—every day! That much milk would leave little room for the other foods you need to eat to have a balanced diet. And while salmon is good, it is still important to eat a variety of foods daily from all the food groups to get all the nutrients you need.

In addition to the foods you eat, you can take a vitamin D supplement to help you reach the recommended daily intake.  An excess of vitamin D from supplements can be toxic to body. So, before starting a supplement, make sure you talk to your doctor to find out what your vitamin D level is and how much you should take.

Vitamin D is important for strong bones, good growth, and a healthy immune system. So…yes.  Do the D!

Authored by: Laura Baily, DTR, and Valerie Peterson, RD

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