What you might not know about Vitamin D

So, in the press you hear a lot about vitamin D and how you can get it from the sun. However, it's not as easy as you think. In the winter, only people who live south of Atlanta, GA can get vitamin D from the sun, until March. This is because the UV rays in the north are not strong enough, and it is the UV rays interacting with cholesterol in the skin that create vitamin D.
For those of us lucky enough to live south of Atlanta, and for everyone when it's not winter, spend 15 minutes per day in the sun to get your full load of vitamin D. However, wearing sunscreen, or being behind a window (such as in your car) prevents vitamin D synthesis (creation).
Some foods these days are being fortified with vitamin D, such as milk, and the only naturally wide-spread sources of food that contain vitamin D are eggs, butter and liver. However, the amount of butter needed to get enough vitamin D is not a healthy amount, and hardly anyone I know would eat liver. So, eggs are a good source, but even for eggs, eating more than one a day gives you a lot of cholesterol.
So, my recommendation, as a future RD and being taught by one in class today, is to take a vitamin D supplement unless you live in Florida or another southern state and are in the sun a lot.