Vitamin A is required for several essential life processes, including metabolism, haematopoeisis, bone development, pattern formation during embryogenesis, the maintenance of differentiated epithelia, and immune-competence.
These processes can be supported by all forms of vitamin A, including the pro-vitamin A carotenoids. The other vitamin functions namely in reproduction, growth, the maintenance of skin and mucous membranes and the visual process, require either retinol or retinaldehyde.
As such, beta-carotene appears to help protect the body against a variety of disorders, including cancer and heart disease.
Vitamin A is known to be involved in fetal development and in the regulation of proliferation and differentiation of many types of cells throughout life. The effects of vitamin A on cellular differentiation are due to the control of gene expression by retinoic acid in selected tissues, the protein products being responsible for the effects.
It plays a role in immune function, both as a cell regulator and by helping maintain the skin and mucous membranes.
Roles of vitamin A in human body