Traditionally they are classified according to their solubility water and fat solvents and, from a physiological standpoint; this property determines the pattern of transport excretion and storage within the human body. Solubility bestows on vitamins many of their characteristic behaviors such as how they are absorbed, transported, stored and utilized.
The body handles the water-soluble vitamins differently from the way it handles the fat-soluble vitamins.
They are absorbed into portal blood in contrast to fat-soluble vitamins and with exception of cobalamin (vitamin B12), they cannot be retained for long periods by the body.
The body absorbs water-soluble vitamins easily and just as easily excretes them in the urine. A few of the water-soluble vitamins can remain in the lean tissues for a month or more, but these tissues actively exchange materials with body fluids all the times.
At any time, the vitamins may be picked up by the extracellular fluids, washed away by the blood and excreted the urine. Therefore, water-soluble vitamins need to be consumed more frequently that fat-soluble ones.
This means a greater risk of deficiency with the water-soluble vitamins with a low risk of toxicity.
Introduction to water soluble vitamins
