We can classify vitamins into two main categories, 1)fat-soluble, and 2)water-soluble. Being soluble simply means having the ability to dissolve in. Therefore, fat-soluble vitamins can dissolve in fat, and water-soluble vitamins have the ability to dissolve in water. By dissolving in water or fat, vitamins can then be absorbed by, transported into, and utilised by the body.

The fat-soluble vitamins include vitamins A, D, E, and K. The fat-soluble vitamins tend to be stored in the body in moderate amounts compared to water-soluble vitamins, and they are not normally excreted in the urine.

Water-soluble vitamins are all the vitamins that are soluble in water (ie., all but A, D, E, and K, which are fat-soluble). Basically, the water-soluble vitamin group contains all the vitamins other than A, D, E, and K. The water-soluble vitamins are excreted in the urine, compared with the fat-soluble vitamins, which are not. The other main difference between the two groups is the water-soluble vitamins are not stored in the body in any appreciable amount. Already, you have some useful information. By knowing that water-soluble vitamins are not stored in the body, we then realize that we must replenish these vitamins often.

Each vitamin is designated by its own letter. Denoting a particular vitamin by a letter makes it both easy to identify and of course, quicker to write. For example, ascorbic acid is given the letter "C". These designations are less cumbersome, yet still convey the vitamin. Let's construct a simple list some of the common vitamins that we may have heard of, and their letter designations.

vitamin A - this is a collective term for retinol and related compounds.

vitamin B complex - A group of more than a dozen water-soluble substances.

vitamin C - ascorbic acid

vitamin D - ergocalciferol

vitamin E - tocopherol and other related compounds with antioxidant activity.

vitamin K - phytonadione and others in this group of structurally related compounds which promote blood clotting

Classification II