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Thirteen vitamins are universally recognized at present. Vitamins are classified by both biological and chemical activity, and not their structure. Vitamers by definition are convertible to the active form of the vitamin in the body, and are sometimes inter-convertible to one another as well. Vitamins have diverse biochemical functions. Although these roles in assisting enzyme-substrate reactions are vitamins’ best-known function, the other vitamin functions are equally important. Study of structural activity, function and their role in maintaining health is called vitaminology. Each vitamin is typically used in multiple reactions, and therefore most have multiple functions.
Drowsiness or muscle relaxation with large doses. Increased congestive heart failure seen in one large randomized study. Vitamins are essential for the normal growth and development of a multicellular organism. It requires certain vitamins and minerals to be present at certain times.
If there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease. Even minor deficiencies may cause permanent damage. For the most part, vitamins are obtained with food, but a few are obtained by other means. Humans can produce some vitamins from precursors they consume. Other findings suggest that vitamin E toxicity is limited to only a specific form when taken in excess. The European Union, United States, Japan and some other countries each set ULs. Scientific evidence supports the benefits of dietary supplements for persons with certain health conditions.
In some cases, vitamin supplements may have unwanted effects, especially if taken before surgery, with other dietary supplements or medicines, or if the person taking them has certain health conditions. They may also contain levels of vitamins many times higher, and in different forms, than one may ingest through food. The table below shows whether various vitamins are susceptible to loss from heat—such as heat from boiling, steaming, frying, etc. The effect of cutting vegetables can be seen from exposure to air and light. Water-soluble vitamins such as B and C dissolve into the water when a vegetable is boiled, and are then lost when the water is discarded. C deprivation in humans have varied widely, from a month to more than six months, depending on previous dietary history that determined body stores. Deficiencies of vitamins are classified as either primary or secondary.