Vitamin D is called the “sunshine vitamin” because it’s produced in your skin in response to sun's rays. It’s a fat-soluble vitamin in a family of compounds that includes vitamins D-1, D-2, and D-3. Your body produces vitamin D naturally when it’s directly exposed to the sun. You can also get it through certain foods and supplements to ensure adequate levels of the vitamin in your system. Vitamin D can be sourced from seafood, cheese and egg yolks.