Vitamin A is an essential fat-soluble bioactive, also known as retinol. There are 2 forms of vitamin A available in the diet: preformed and provitamin A. Preformed vitamin A comes from animal sources, with high concentrations in fish oils, eggs and milk. Provitamin A comes from plant sources and is mainly found in the form as carotenoids with the most important one: beta-carotene. The body converts these provitamin carotenoids into vitamin A.
Both preformed vitamin A and provitamin A must be metabolized intracellularly to retinal and retinoic acid, the active forms of vitamin A, to support the vitamin’s important biological function. Vitamin A plays a key role in several bodily functions including:
Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors. Vitamin A maintains vision because it continuously forms new rhodopsin. Retinoic acid, is a substitute of vitamin A and supports the conjunctival membranes and cornea.
Growth and development
Vitamin A is involved in genetic regulation of cell formation and differentiation and intercellular communication. It is critical during the (neurological) development of the foetus.
Vitamin A also supports the immune system and helps to protect against infections and invading antigens.
Skin and mucous membranes
The skin is a mechanical immune barrier, and sufficient concentrations of vitamin A available, maintain skin health.
The European Food Safety Authority (EFSA) has acknowledged the following beneficial effects of preformed vitamin A and provitamin A as a basis for health claims:
• Normal cell differentiation
• Normal function of the immune system
• Maintenance of normal skin and mucous membranes
• Maintenance of normal vision
• Normal metabolism of iron