各种维生素的作用（The role of vitamins）.docVIP

各种维生素的作用（The role of vitamins） The effects of various vitamins Vitamin A Vitamin A is a fat soluble vitamin that is stored in the liver. It is mainly used to improve vision and enhance immune system function. There are two kinds of vitamin A. One is vitamin A alcohol (retionl), which is the original form of vitamin A (found only in animal foods); the other is a beta carotene (carotene), in the human body can be transformed into vitamin A prefabricated material. Because of these two forms of vitamin A determines the main source of vitamin A is two, one is Cod Liver Oil, beef, chicken, eggs and dairy products, they contain vitamin A alcohol; another is vegetables such as carrots, spinach, peas, red sweet potatoes, green pepper, pumpkin, amaranth, leek etc. yellow yellow green vegetables and fruits, they contain beta carotene, and the effects of beta carotene in the liver and intestine of human and animal carotenoid enzymes, can be converted into vitamin A, so eating more vegetables can guarantee enough vitamin A. Since vitamin A and carotene are insoluble in water and soluble in fat, food containing vitamin A and beta carotene is associated with fat intake, which promotes their absorption. But in daily life, vitamin A beta carotene is used more when vitamin supplements are added, because beta carotene does not have the potential toxicity of vitamin A alcohol. Vitamin A deficiency is wound healing ability is poor, easy to be infected, night blindness from light to dark and difficult to adjust the vision. Vitamin A in the body too much, a lot of human intake of vitamin A, as the discharge ratio is not high, because some are often stored in the body caused by poisoning, symptoms usually manifested as skin dry, brittle nails, hair loss, weight loss, easy irritability, headache and fatigue. The recommended daily intake of vitamin A amounts to 5000IU per day for men and 4000IU per day for women. But because vitamin A can be stored in the body, it does not require daily supp