Vitamins may be regarded as organic compounds required in the diet in small amounts to perform specific biological functions for normal maintenance of optimum growth and health of the organism. Vitamins are classified by their biological and chemical activity.
There are 13 vitamins human body needs. They are vitamins A, C, D, E, K and the B vitamins (thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B-6, vitamin B-12 and folate).
Usually all vitamins are obtained from foods we eat. Human body can also make vitamins D and K. People who eat a vegetarian diet may need to take a vitamin B12 supplement.
Vitamins are classified as either water-soluble or fat soluble.
Water-soluble vitamins dissolve easily in water, and in general, most of these vitamins are readily excreted in urine thus, urinary output is a strong predictor of vitamin consumption. They are not toxic to the body. Many types of water-soluble vitamins are synthesized by bacteria. Vitamin B and C are water soluble.
These are a heterogeneous group of compounds since they differ chemically from each other. Water soluble vitamins are not stored in the body in large quantities (except B12). For this reason, they must be continuously supplied in diet. They form coenzymes that participate in a variety of biochemical reactions, related to either energy generation or hematopoiesis.
There are eight types of vitamin B:
- Thiamin (B1)
- Pantothenic acid
- Vitamin B6 (pyridoxine)
- Folate (called folic acid when included in supplements)
- Vitamin B12 (cyanocobalamin).
Fat-soluble vitamins are absorbed through t intestinal tract with the help of lipids (fats). They are more likely to lead to hypervitaminosis than water-soluble vitamins because they are more likely to accumulate in the body. Fat-soluble vitamin regulation is of particular significance in cystic fibrosis. (A, D, E and K) are fat-soluble vitamins.
Their availability in diet absorption and transport are associated with fat. They are soluble in fats and oils and also the fat solvents (alcohol, acetone etc.). They can be stored in liver and adipose tissue and are not readily excreted in urine. Excess consumption of these vitamins (particularly A and D) leads to their accumulation and toxic effects. All these vitamins are isoprenoid compounds, since they are made up of one or more of five carbon units namely isoprene units (-CH=C.CH3-CH=CH-).
Fat-Soluble vitamins participate in diverse processes such as Blood Clotting and Vision.
It represents chemically similar substances that possess qualitatively similar activity as that of vitamin. Some good examples of vitamers are:
- Retinol, Retinaland and Retinoic acid etc. are vitamers of vitamin A.
- Pyridoxine, Pyridoxal and Pyridoxamine etc. are vitamers of vitamin B.