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Generalities and distribution in nature ô Vitamin A ô Vitamin C ô Vitamin D ô Vitamin E ô Vitamin K
Generalities and distribution in natureVitamins are essential nutrients for the human organism: they are not obtainable via metabolic functions but must be exclusively introduced in the body through a balanced diet. They play a vital role as bio-regulators adjusting metabolic processes and cell activity; the necessity of vitamin consumption varies according to age, the degree of physical and mental activity, physiological conditions and particular diet habits. They are found in most foods and for this reason one can obtain the minimum requirement by eating a balanced diet, thus preventing any symptomatic conditions of diseases connected to various vitamin deficiencies. Vitamins are characterised by their ability to be soluble and are divided into two groups: fat-soluble and water-soluble. The fat -soluble vitamins are: A, D, E, K, and the principal water-soluble ones are Vitamins B1, B2, PP, B6, B12, C.
Vitamin AFor its specific function linked to the activity of the eye's retina and for its chemical composition, vitamin A has earned the name "retinol". It is present in animal tissue as such whereas in the vegetable group its precursors are found in association with chlorophyl: carotenes, red and yellow pigments which are present in carrots and in certain leafy vegetables. Carotenes are considered pro-vitamins since they are transformed, by hydrolysis, in vitamins in animals. The conversion of carotenes into retinol occurs in the intestinal mucous, while it is stored in the liver.
Vitamin D or cholecalciferolJust like other fat solubles, vitamin D is also absorbed in the intestines together with fats. The main organ for storage is the liver. There are various forms of vitamin D, however the principle ones are represented by vitamin D2 which derives from ergosterol (pro-vitamin D2 ) of vegetable sources and by vitamin D3 which derives from7-dihedrol- cholesterol ( pro-vitamin D3) of animal sources. Both are transformed in an active form through photo-chemical action of the sunlight's ultraviolet rays on skin tissue.
Vitamin E or tocopherylVitamin E is found in nature in diverse forms that are chemically similar to one another. The most active form is one defined as alpha-tocopheryl and is especially present in wheat germ oil. These substances remain stable when exposed to light and heat ( in the absence of oxygen ) but are rapidly altered when exposed to ultra-violet rays. They are particularly sensitive to oxygen and any oxidating substance. Tocopheryl in foods are absorbed in the intestines by the same process as other fat-soluble elements. If they’re administered in large quantities, the excess is eliminated through the faeces and in traces in the urine.
Vitamin KVitamin K encompasses a group of substances all sharing a common hemorrhagic property. Natural vitamin K includes K1 and K2 while the analog synthetic substance which acts as a vitamin K, is called K3. Vitamin K is synthesised intestinal flora bacteria; it’s contained in the microorganisms of plants and animal. It is utilised in the liver where it is stored in small quantities
Vitamin C or Absorbic acidIt is valued for its effectiveness in treating the vitamin C deficiency disease named scurvy. Vitamin C is absorbed in the small intestines and is passed through the bloodstream and then stored in the liver, hypophysis, thymus and the adrenal cortex. An excess of absorbic acid is subsequently eliminated in the urine and the faeces and through perspiration in a minimum amount. Heat and poor storage factors tend to inactivate the efficiency of this molecule.
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