Most of them are obtained from the diet, basically fruits and vegetables. The microorganisms in the intestine synthesize vitamin K and vitamin B12. Vitamin D is synthesized by the skin with the help of ultraviolet wavelength of natural sunlight.

They are classified as fat-soluble (A, D, E and K) and water-soluble (C and B-group). The water-soluble vitamins are readily excreted in urine. Vitamins have diverse functions. They function as hormones (Vitamin D regulates the levels of calcium and phosphate in the blood.), as antioxidants (vitamin E), regulate the cell development and growth and act as mediators of cell signaling. Some act as enzyme cofactor bio-molecules (coenzymes). Some assist the enzymatic action and some take part in it.

To avoid deficiencies they must be continuously supplied in the diet. Vitamin deficiencies can be classified as primary deficiency and secondary deficiency.

• Primary deficiency is due to the decreased intake of the vitamins.

• Secondary deficiency is due to an underlying cause or disorder that either does not allow proper absorption or usage of the vitamins.

If the required amount of vitamins cannot be obtained by varied diet, dietary supplements are given to prevent deficiencies and in cases of secondary deficiency, the underlying cause needs to be identified and treated appropriately.

However, care needs to be taken to avoid over dosage of vitamins to avoid serious complications.