Vitamins
Definition: The vitamin concept has undergone extensive revisions during the history of biochemistry. However, Franz Holfmeister's definition-" Vitamins are substances which are indispensable for the growth and maintenance of the animal organism, which occur both in animals and plants and are present in only small amounts in food'- still holds good, although it has been interpreted in various ways.
General characteristics of vitamins
The vitamins are characterized for some general facts, which are listed below:
- Vitamins are of widespread occurance in nature, both in plant and animal worlds.
- All common foodstuffs contain more than one vitamin.
- The plants can synthesize all the vitamins where as only a few vitamins are synthesized in animals.
- Human body can synthesize some vitamins, e.g vitamin A synthesized from its precursor carotene and vitamin D from ultraviolet radiation of ergosterol and 7- dehydrocholesterol. Some members of the vitamin B complex are synthesized by microorganisms present in the intestinal tract. Vitamin C is also synthesized in some animals such as rat.
- Most of vitamins have been artificially synthesized.
- All the cells of the body store vitamins to some extent.
- Vitamins are partly destroyed and ar partly exerted.
- Vitamins are nonantigenic.
- Vitamins carry out functions in very low concentrations. Hence, the total daily requirement is very small.
- Vitamins are effective when taken orally.
- Synthetically made vitamins are just as nutritionally good as natural vitamins.
- Old people need about the same amounts of vitamins as young people.