There are two chemical forms of vitamin D, namely vitamin D2 and vitamin D3. The natural form of vitamin D for animals and man is vitamin D3 that is produced in their bodies from cholesterol and 7-dehydrocholesterol. An alternative vitamin D2 is derived from the yeast sterol ergo sterol by chemical procedures. Vitamin D is an essential vitamin required by the body for the proper absorption of calcium, bone development, control of cell growth, neuromuscular functioning, proper immune functioning, and alleviation of inflammation.
One of the easiest ways to ensure one has enough vitamin D is to always be exposed to a little sunlight. Since vitamin D3 is produced in the skin after exposure of 7-dehydrocholesterol to sunlight, the human does not have a requirement for vitamin D when sufficient sunlight is available. Thus vitamin D3 does become an important nutritional factor in the absence of sunlight.
Various types of fish are high in vitamin D. Typically raw fish contains more vitamin D than cooked and fatty cuts will contain more than lean cuts. Fish canned in oil will have more vitamin D than those canned in water. Raw fish is typically eaten in the form of sushi. Raw Atlantic Herring provides the most vitamin D.
Soy products are often fortified with both vitamins D, dairy products are already high in calcium, so it makes sense to fortify them with vitamin D. Mushrooms are high in vitamin D Lightly cooked white button mushrooms provide the most vitamin D with 27.0IU (7% RDA) per 100 gram serving, or 7.6IU (2% RDA) per ounce. Eggs are also high in vitamin D they provide 9% of a daily requirement in a large fried egg.
Cod liver oil has been a popular supplement for many years and naturally contains very high levels of vitamin A and vitamin D. Cod liver oil provides 10001IU (1667% RDA) per 100 gram serving, or 1360IU (340% RDA) in a single tablespoon