The main role of vitamin A is in vision. However, it also plays a role in growth, reproduction and in the immune system.
Vitamin A may exist in its pre-formed state; carotene or as retinol in the diet. Carotene is converted to vitamin A
in the intestine, liver and kidney. Vitamin A and its precursors are absorbed with fat in the intestine. It is then stored in the liver and transported around the body attached to retinol binding protein, a transporter.
Vitamin A is found mainly in foods of animal origin including milk products, margarines, butter, egg yolk, liver
and fish liver oils. Carotenes are found in dark green leafy vegetables, deep yellow vegetables, tomatoes and yellow fruit.
First signs of vitamin A deficiency include night blindness leading to bitots spots and later xerophthalmia. One important additional effect of Vitamin A deficiency is a lowered immune response, leading to a lowered resistance to infection. Vitamin A deficiency is commonly found in southern and eastern Asia, parts of Latin America, and in many countries