In 1912 Hopkins noticed that in addition to carbohydrates, proteins and fats there are other substances needed for normal growth. Although these substances were needed in small quantity, yet these substances were called Accessory Growth Factors. Later Funk proposed the name Vitamin for these substances. He discovered Vitamin Bi (Thiamin).
13.5.1 Types of Vitamins
Vitamins are divided into two types:
(i) Fat Soluble Vitamins
The vitamins which dissolve in fats are called fat soluble vitamins. These are vitamin A, D, E and K. If these vitamins are taken in large quantity, they accumulate in the body and cause diseases. For example, accumulation of vitamin D in the body causes bone- pain and bonelike deposits in the kidney. However, their deficiency also causes diseases. Sources, uses and diseases because of deficiency are provided in the Table 13.1.
| No | Vitamin | Sources | Uses | Diseases |
|---|---|---|---|---|
| i | Vitamin A | Dairy products, eggs, oils and fats, fish. It can also be obtained from the beta-carotene found in green vegetables, carrots and liver. | Maintain the health of the epithelium and acts on the retina's dark adaptation mechanism. | Night blindness, eye inflammation. |
| ii | Vitamin D | Fish liver, dairy products, oils and fats, Vitamin D is formed in the skin when it is exposed to sunlight. | Has a role in the absorption of calcium, which is essential for the maintenance of healthy bones. | Rickets |