What Vitamin D is: Vitamin D is a fat-soluble vitamin that is naturally present in only a few foods. Most children won't get enough Vitamin D from food alone. Foods that contain Vitamin D include fatty fish like salmon, herring, mackerel and sardines. Small amounts of Vitamin D are found in beef liver, cheese and egg yolks. Vitamin D is also produced by the body. When the sun shines on the skin it triggers the skin to make Vitamin D. It should not be assumed that children get enough Vitamin D from the sun.