Vitamin A and Beta-Carotene

Vitamin A

• Vitamin A was the first fat-soluble vitamin to be recognized
• Vitamin A and its precursor, beta-carotene, are still an area of research

Forms of Vitamin A

• There are 3 active forms of vitamin A: Retinol, Retinal, and Retinoic acid
• Retinol is an antioxidant nutrient stored in the liver
• Retinal is converted by the cells to retinol as needed

Roles of Vitamin A

• Gene expression
• Vision
• Maintenance of body linings and skin
• Immune defenses
• Growth of bones and of the body
• Normal development of cells
• Reproduction

Vitamin A in Eyesight

• Vitamin A plays 2 roles in eyesight: in the process of light perception at the retina and in the maintenance of a healthy cornea
• Rhodopsin, a pigment in the retina, contains vitamin A, which breaks off when light falls on the eye and reunites with the pigment after bleaching
• A lack of vitamin A can cause night blindness

Night Blindness

• Night blindness occurs when the vitamin A supply is low, causing a lag before the eye can see again after a flash of bright light at night

Xerophthalmia and Blindness

• A more profound deficiency of vitamin A causes keratinization of the cornea, leading to xerophthalmia (drying) and permanent blindness
• Half a million vitamin A-deprived children become blind each year due to xerophthalmia

Gene Regulation

• Retinoic acid, a form of vitamin A, regulates hundreds of genes that direct the synthesis of proteins that perform metabolic work in tissues
• Vitamin A affects the metabolic activities of tissues and, in turn, the health of the body

Cell Differentiation

• Vitamin A is needed for cell differentiation in epithelial tissue, such as the protective linings of the lungs, intestines, vagina, urinary tract, and bladder
• Cell differentiation is essential for the development of specific cell functions, such as mucus production in goblet cells
• Vitamin A deficiency leads to the failure of cells to make mucus, allowing keratin to accumulate and making tissues vulnerable to infection

Immune Function

• Vitamin A has an "anti-infective" reputation and is essential for immune defenses
• A lack of vitamin A weakens the body's defenses, making illness more severe

Reproduction and Growth

• In men, vitamin A is necessary for the formation of sperm
• Vitamin A is essential for reproduction and growth

Learn about Vitamin A, the first fat-soluble vitamin to be recognized, and its plant-derived precursor, beta-carotene, which has antioxidant activity. Explore their functions and food sources.