The recommended daily allowance of vitamin D established by the Food and Nutrition Board of the Institute of Medicine for adults ages 19 to 50 is 600 international units or 15 micrograms. These values are recommended based on minimal sun exposure.
Vitamin D occurs naturally in only a few foods. These include swordfish, salmon, tuna, beef liver and eggs. Milk, yogurt, orange juice and cereal are often fortified with the vitamin to provide other sources to consumers. It is available as a supplement also.
Sunlight allows the body to convert pre-existing chemicals in the body to vitamin D. Risk of skin cancer causes health professionals to recommend food sources over intentional sunlight exposure to provide the vitamin.