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Vitamin Chenhao Li Vitamin A vitamin is an organic compound required as a vital nutrient in tiny amounts by an organism . In other words, an organic chemical compound (or related set of compounds) is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. List of vitamins Vitamin A Vitamin A (or Vitamin A Retinol, retinal, and four carotenoids including beta carotene ) is a vitamin that is needed by the retina of the eye in the form of a specific metabolite , the light-absorbing molecule retinal , that is necessary for both lowlight ( scotopic vision) and color vision . Vitamin A also functions in a very different role as an irreversibly oxidized form of retinol known as retinoic acid , which is an important hormone-like growth factor for epithelial and other cells. Vitamin B B vitamins are a group of water-soluble vitamins that play important roles in cell metabolism .The B vitamins were once thought to be a single vitamin, referred to as vitamin B (much as people refer to vitamin C or vitamin D ).Later research showed that they are chemically distinct vitamins that often coexist in the same foods. Vitamin C Vitamin C or L- ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species.In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress . It is also a cofactor in at least eight enzymatic reactions including several collagen synthesis reactions that, when dysfunctional, cause the most severe symptoms of scurvy . In animals these reactions are especially important in wound-healing and in preventing bleeding from capillaries. Vitamin D Vitamin D is a group of fat-soluble.In humans, vitamin D is unique because it can be ingested as cholecalciferol (vitamin D 3 ) or ergocalciferol (vitamin D 2 ) and because the body can also synthesize it (from cholesterol) when sun exposure is adequate (hence its nickname, the "sunshine vitamin"). vitamin E Vitamin E refers to a group of eight fat-soluble compounds that include both tocopherols and tocotrienols . There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γTocopherol can be found in corn oil, soybean oil, margarine and dressings. α-Tocopherol , the most biologically active form of vitamin E, is the second most common form of vitamin E in the North American diet. Vitamin k Vitamin K 1 , also known as vitamin K j , phylloquinone or phytomenadione (also called phytonadione), is synthesized by plants, and is found in highest amounts in green leafy vegetables because it is directly involved in photosynthesis. diseases cause by lack of vitamin For example, lack of vitamin A can cause night blindness, lack of vitamin B1 can cause beriberi, lack of B3 can cause Pellagra, lack of vitamin C can cause scurvy, and lack of vitamin D can cause rickets in children and osteoporosis. diseases cause by lack of vitamin For example, lack of vitamin A can cause night blindness, lack of vitamin B1 can cause beriberi, lack of B3 can cause Pellagra, lack of vitamin C can cause scurvy, and lack of vitamin D can cause rickets in children and osteoporosis. Vitamin and mineral supplements If you don't eat a nutritious variety of foods, some supplements might help you get adequate amounts of essential nutrients.However, supplements can't take the place of the variety of foods that are important to a healthy diet.Scientific evidence shows that some dietary supplements are beneficial for overall health and for managing some health conditions.For example, calcium and vitamin D are important for keeping bones strong and reducing bone loss; folic acid decreases the risk of certain birth defects; and omega-3 fatty acids from fish oils might help some people with heart disease. END