What is the function of vitamin A? Vitamin A is the nutrient to eat for a perfect vision. There are two types of vitamin A: retinol from animal foods and precursors of vitamin A – carotenes (beta-carotene, alpha-carotene, gamma-carotene and beta-cryptoxanthin) from plant foods.
The essential nutrients plays a crucial part in a number of physiologic processes that ensure the good functioning of multiple systems and organs, from the immune system to eyesight and skin.
Vitamin A is vital for healthy epithelial tissues and mucous membranes, exerts antioxidant properties that help protect skin from free radical damage and helps maintain skin elasticity. It further regulates skin cell growth and differentiation.
The essential nutrient supports bone growth and development and the formation of tooth enamel and thus promotes strong bones and teeth. It further contributes to good fertility and the normal development of babies in the womb, making it important to meet daily requirements during pregnancy.
Vitamin A facilitates vision adaptation to low light conditions and is vital for color vision as well as good visual acuity. Moreover, it increases resistance to infection and scavenges free radicals thanks to its immune system-modulating and antioxidant properties. It helps immune system cells such as T-cells differentiate and mature and, because it maintains the overall health of mucous membranes, it supports healthy populations of immune system cells in the intestinal tract for better immunity. Vitamin A is fat-soluble meaning it gets absorbed in the presence of dietary fat, whether from the same foods it is also found in (in the case of retinol) or from other foods it is paired with during a meal (in the case of carotenes from plant sources). 
Vitamin A deficiency symptoms include: poor immunity, frequent infections (viral or bacterial, respiratory tract or other kind), poor night vision, problems seeing well in low light conditions, poor visual acuity, blindness (in case of a severe deficiency), dry eyes, dry and cracked skin occurring on various parts of the body, tooth erosion caused by loss of enamel, even birth defects in severe cases.