Vitamin D is a fat-soluble vitamin, it is seen as a role in calcium and phosphorus metabolism of the body before the hormone, which is closely related with the sun, it is also called the "sunshine vitamin." Vitamin D3 (cholecalciferol) is mainly synthesized by the body itself, the body's skin contains a cholesterol, after sun exposure, it becomes a vitamin D3. So, if the child can fully accept the skin over 4-6 hours of direct sunlight, then own synthesis of vitamin D3, it can basically meet. But skin cancer caused by ultraviolet radiation rise, under the influence of air pollution, weather changes and other issues around the countries of the time people accept sunshine declining, and many countries want to limit the acceptance of sunshine clearly defined period of time, and therefore worldwide vitamin D deficiency showed widespread phenomenon. In addition, vitamin D3 can also come from animal foods such as liver class, especially from fish and seafood in the liver of cod liver oil refining. In addition to the presence of vitamin D3 in addition to a small number of animal food, mainly in the skin after exposure to ultraviolet light 7- dehydrocholesterol formed, while 7- dehydrogenation cholesterol level is generated by changes in cholesterol, so some people call it the sun vitamin Vitamin D3 is a fat-soluble, insoluble in water, soluble only in fat or fat solvents, in neutral and alkaline solution to high temperature and oxidation. According to the experiment, was heated at 130C for 90 minutes, and its physiological epidemic still be destroyed, but gradual decomposition under acidic conditions is damaged, general food cooking process plus pattern, without loss, but can cause failure when the fatty acid Vitamin D3 destruction. Vitamin D3 unit of measurement, there are two, namely weight units and international units. 1 is equivalent to 40 micrograms of D3 international units; or an equivalent international units of vitamin D3 cholecalciferol 0.025 micrograms.