Vitamins is a word which is commonly heard. Advertisers claim that their products contain some vitamins or the other which is good for health, etc. but, what is a vitamins? Does it really play an important role in our health?
A vitamin is a vital substance. It is needed in a very small quantity for growth and good health. Vitamins are vital body regulators. They may be defined as a name given to a group of potent organic compounds which are not carbohydrates, protein or fats in nature, but are present in foods and are essential in minute quantities for specific body functions of growth, maintenance and reproduction. Most of them are not synthesized by the body and must be supplied through diet, except a few whose requirement may be partially met by synthesis in the body, such as folic acid and vitamin D.
Nomenclature of vitamins
Numerous scientists have contributed to the discovery of vitamins. The word vitamin was coined by Casimir funk who discovered a water-soluble substance in rice polishing which prevented beri-beri. He described this vitamin as a vital amine. Hence, he named the substance vitamin.
Classification of vitamins:-
Vitamin are classified according to their solubility in fat and water.
- Fat-soluble vitamins are A, D, E and K
- Water-soluble vitamins are B group vitamin and vitamin C
It is necessary to explain the term provitamin here. A provitamin is a substance which the human body can convert into the vitamin, eg beta carotene, dehydrocholesterol and ergosterol are provitamins of vitamin D.
Chemical characteristics of fat-soluble vitamins are:-
- They are not easily destroyed by ordinary cooking methods.
- They are stored in the body and, at times, cause toxicity when supplied in excess. This phenomenon is called hypervitaminosis. It is deal with individually under each fat soluble vitamin.
- They are destroyed by rancidity as they are always associated with fats.
- They are not absorbed if mineral oil is present in the intestine.
Chemical characteristic of water soluble vitamins are:-
- Compared to the fat-soluble vitamins they are unstable since they are easily affected by factors such as heat, heat, light, oxidation, radiation, contamination by metals, etc.
- They are affected by preparation practices, eg if the water in which the food is cooked (some vitamins are mixed with the water) is thrown away.
- Excess intake of these vitamins results in urinary excretion of the surplus that the body cannot retain.