VITAMINS AND THEIR MEDICAL RELEVANCE

Vitamins are nutritional requirements needed in small amounts by animals for healthy living. Vitamins are classified into 2 groups; water-soluble vitamins and fat-soluble vitamins. Examples of water-soluble vitamins are vitamin C (ascorbic acid) and the B vitamins(i.e vitamin B1,vitamin B2,vitamin B6 and vitamin B12). Fat-soluble vitamins include vitamin A, vitamin D, vitamin E and vitamin K.




Water-soluble vitamins have diverse chemical structures and are polar molecules. They can be synthesized by plants and are therefore provided by food sources such as legumes, whole grains, green leafy vegetables , yeast ,meat and milk. Water-soluble vitamins serves as co-factors (co-enzymes) in enzymatic reactions.




With the exception of vitamin B12 (cyanocobalamin),water-soluble vitamins are not stored in the body. Continuous intake in the diet is required. The human liver can store vitamin B12. They are absorbed in the water along the gastrointestinal tract and are excreted easily along with urine.




Water-soluble vitamins occur in interrelated biochemical pathways and deficiency diseases caused by lack of a single vitamin is rare. Generally ,lack of water-soluble vitamins affect tissues that are growing or metabolizing rapidly such as skin, blood, the digestive tract and the nervous system.




Symptoms of their deficiency include dermatitis, beri-beri, anaemia ,pellagra ,digestive and neurologic disorders. Ascorbic acid (vitamin C) is liable to heat including other water-soluble vitamins. Other important B vitamins include pantothenic acid (vitamin B5), biotin, folic acid (pteroylglutamic acid).



Fat-soluble vitamins are absorbed along with fats in the body. Hence, any substance or factor that favours the absorption of fats and lipids would aid their absorption. Fat-soluble vitamins include vitamin A, vitamin D, vitamin E and vitamin K respectively.



Vitamins A is derived from the precursor beta carotene. Cleavage at the centre of the structure produces retinol. It functions as a hormone. Food sources include fish liver oils, whole milk, carrots and sweet potatoes. Deficiency of retinol results in a variety of symptoms such as dryness of skin, eyes, mucous membranes and night blindness.




Vitamin D is one of the isoprenoid compounds. It exists in diverse forms such as cholecalciferol(vitamin D3),ergocalciferol (vitamin D2). Vitamin D3 is the precursor of 1,25-dihydroxycholecalciferol,a hormone that regulates calcium metabolism. Deficiency of vitamin D results in rickets and bone diseases such as osteomalacia,osteoporosis.



Vitamin E is also referred to as tocopherol. Vitamin E associates with cell membranes, lipid deposits and blood lipoproteins. They serve as biological anti-oxidants. Dietary sources include eggs and vegetable oil. Deficiency of vitamin E results in scaly skin, muscular weakness, and fragile erythrocytes.



Vitamin K has subgroups such as vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). Vitamin K possess an aromatic ring. Detailed research discovered vitamin K as a required factor for blood clotting. Deficiency of vitamin K results in avitaminosis. Steatorrhea and biliary system disorders can result in malabsorption of the fat-soluble vitamins.




Vitamins are essential nutritional requirements required in the life processes of humans. Hence ,fat-soluble vitamins should be consumed with care since they can accumulate in the body to cause metabolic problems. Water-soluble vitamins should be continuously supplied in the diet.