Skin makes vitamin D when exposed to the sun. Since the sun also causes the majority of skin cancer, dermatologists recommend getting Vitamin D from the diet not, the sun.
The Skin Cancer Foundation recommends 1000 IU of vitamin D per day, for adults.
The American Academy of dermatology Position statement can be viewed here (PDF).
Vitamin D is toxic in high doses - 2000 IU is the upper daily limit for safety.
Calculate your average dietary intake of vitamin D. Take a supplement, if necessary, to meet the 1000 IU/day
Natural sources can vary widely in vitamin D content.
Methods of food preparation can affect vitamin D content.
Natural sources include:
Fortified sources base the percentage on 400 IU(25% equals 100 IU)
Fortified sources include:
Baking did not change the content of vitamin D in farm raised salmon but, frying reduced the content by 50%