Vitamin A is a fat soluble vitamin, an organic compound with the chemical formula C20H30O. It is stable to heat, acid, and alkali, and is easily oxidized. Ultraviolet radiation can promote its oxidative damage. Vitamin A includes A1 and A2, with A1 being retinol. Vitamin A2, also known as 3-dehydroretinol, has a physiological activity that is 40% of that of vitamin A1. Vitamin A has various physiological functions such as promoting growth and reproduction, maintaining normal secretion of bones, epithelial tissues, vision, and mucosal epithelium. Vitamin A and its analogues have the effect of preventing precancerous lesions. When lacking, it manifests as growth retardation, decreased dark adaptation ability, and the formation of night blindness. Due to dryness, desquamation, excessive keratinization, and reduced secretion of lacrimal glands in the epidermis and mucosal epithelial cells, dry eye disease can occur, and in severe cases, corneal softening, perforation, and blindness can occur. Respiratory epithelial cells keratinize and lose cilia, reducing resistance and making them susceptible to infection. The recommended daily intake (RNI) for adult vitamin A in China is 800 μ g retinol active equivalent for males and 700 μ g retinol active equivalent for females.
