What is Vitamin?
Vitamins are nutrients that our body needs to function and fight off disease. Our body cannot produce vitamins itself, so we must get them through food we eat or in some cases supplements. So, Vitamins are essential organic constituents of food other than carbohydrate, protein and fat, required in minute quantities for maintaining normal growth and metabolism, proper functioning of the body and good health.
How the vitamins are named?
Vitamins are named in three ways. Previously, when their chemical structures were not known, vitamins were named alphabetically e.g., vitamins A, B, C, D, E, K etc. Vitamins were also named according to their functions or clinical uses (i.e., their ability to prevent diseases) e.g., anti-beriberi vitamin, anti-scorbutic vitamin etc., Vitamins were finally named chemically after their chemical structures were revealed e.g., retinol (vitamin A), thiamine (vitamin BI), riboflavin (vitamin B2) and so on.
Classification of vitamins
Vitamins are classified according to their solubility into two main classes—fat soluble vitamins and water soluble vitamins. The fat soluble vitamins are of four types—vitamin A, vitamin D, vitamin E and Vitamin K. Water soluble vitamins include the vitamins of B complex group and vitamin C. The B complex group includes several vitamins such as thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, biotin, folic acid, cobalamins etc.
Fat soluble vitamins
i) Vitamin A - comes from orange colored fruits and vegetables; dark leafy greens, like kale
ii) Vitamin D - can be found in fortified milk and dairy products; cereals; (and of course sunshine!)
iii) Vitamin E - is found in fortified cereals, leafy green vegetables, seeds, and nuts .
iv) Vitamin K - can be found in dark green leafy vegetables and turnip/beet greens.
Water soluble vitamins
i) Vitamin B1 or Thiamin - come from whole grains, enriched grains; liver; nuts, and seeds
ii) Vitamin B2 or Riboflavin - comes from whole grains, enriched grains, and dairy products
iii) Vitamin B3 or Niacin - comes from meat, fish, poultry, and whole grains
iv) Vitamin B5 or Pantothenic Acid - comes from meat, poultry, and whole grains
v) Vitamin B6 or Pyridoxine - comes from fortified cereals and soy products
vi) Vitamin B7 or Biotin - is found in fruits and meats
vii) Vitamin B9 or Folic Acid (Folate) - comes from leafy vegetables
viii) Vitamin B12 - comes from fish, poultry, meat, and dairy products
ix) Vitamin C - comes from citrus fruits and juices, such as oranges and grapefruits; red, yellow and green peppers
Pro-vitamin and Anti-vitamin
A pro-vitamin is the forerunner of a vitamin which when taken through diet is converted to the vitamin in the body. Examples are—Carotene (provitamin A), ergosterol (provitamin D) etc.
On the other hand a compound having chemical structure similar to that of a vitamin may inhibit or antagonise the function of the vitamin is called anti-vitamin. Examples-pyrithiamine, galactoflavin and avidin are antivitamins of thiamine, riboflavin, and biotin respectively.
What is Pseudovitamin?
Pseudoviamin means the false vitamin. Certain organic compounds though structurally similar to some vitamin do not show the physiological actions of the vitamin ; such compounds are called pseudovitamins. Example-methylcobalamine is pseudovitamin of cyanocobalamine or vitamin B12.
The state of deficiency of vitamins is called avitaminosis. Antivitaminosis may be of various types depending upon the type of vitamin being lacking. Each type is characterized by certain signs and symptoms. Avitaminosis is primarily produced by lack of vitamins or presence of anti-vitamins in diet. However, treatment with antibiotic drugs often produces deficiency of certain vitamins of B complex group that are synthesized by intestinal bacteria, because these micro-organisms are killed by the application of antibiotic drugs. For this reason, vitamin B complex should be given during antibiotic therapy.
Intake of excess vitamins may also lead to some pathological conditions that are referred to as hypervitaminosis. However, hypervitarninosis is rare and occurs in case of fat soluble vitamins A and D mainly, because these are not easily excreted from our body through urine and hence may be stored in considerably high amounts. On the other hand, the excess water soluble vitamins can easily be excreted through urine and hence do not accumulate in the body in large quantities to cause hypervitaminosis.