Vitamin A was discovered in the early nineteenth century by Dr. E. Mc Collum. He carried out experiments on rats and found that when butter and egg yolk were added to the diet of a group of rats, they were healthier and stronger are compared to the other group which were fed on lard and vegetables only. Later on this second group developed sign of weakness, they were short, their skin was rough and they developed sign of blindness. Thus he came to the conclusion that butter and egg yolk contain some vital element which were absent in lard and vegetables. In 1913 he isolated vitamin A from butter and egg yolk. It occurs naturally in most animal fats. Commercial synthesis is possible from lemon grass oil.

Composition and properties

Vitamin a consists of carbon hydrogen and oxygen. It is a yellow crystalline substance and occurs in many forms. It occurs in the acid containing the R-COOH group, in the alcohol form as retinal containing the R-OH group, in the aldehyde form as retinal containing the R-C=C-R group.

Carotenes which are synthesised by plants are the ultimate source of vitamin all A. Both men and animal s covert to vitamins A. A considerable proportion of the carotene present in their food. Carotenes are dark red crystalline compounds known also as pro-vitamin A or as precursors of vitamin A’. Alpha beta gamma carotene and cryptoxanthene are of significance in nutrition. each molecules of beta carotene yields two molecule of vitamin A vitamin A does not dissolve in water but it is fat soluble .it does not get destroyed at ordinary level of heat.



Vitamin A is required for proper growth and normal skeletal development of the body .it also essential for healthy teeth structure and the proper activity of the sweat glands.

Vitamins A helps in the maintenance of a healthy, glowing and soft skin due to better formation of the epithelial tissue .this vitamin also play an important role in maintaining proper vision in dim light (night blindness). Foetal tissue may also develop malformation if vitamin a is not present.

Sources of vitamin A


Vitamin A is present in animal foods like butter, ghee, whole milk, curd, and egg yolk and liver. The liver oils of certain fish like cod, halibut and shark are the richest sources of vitamin A.

It not presents as vitamin a in vegetable foods but these substances contain carotene which is converted to vitamin A in the body. Carotene is also known as pro-vitamin A. Leafy vegetables such as spinach, amaranth, coriander leaves, curry leaves, drumsticks, ripe fruit such as mangoes, papaya and tomatoes are rich in carotene. Carrots and yellow pumpkins are also good sources .In general the darker the colour of the green vegetables, the greater is their carotene content.