What is vitamin A and its functions
Vitamin A, also known as retinol, is a fat soluble alcohol substance. It has a higher absorption rate when coexisting with oil, so it belongs to the category of fat soluble vitamins. (Vitamins are divided into fat soluble and water soluble) They are mainly present in animal foods: animal liver, fish liver oil, caviar, whole milk and whole milk products, as well as eggs. Vitamin A plays an important role in the visual production of the human body, and was first used to treat dry eye disease, so it is also known as an "anti dry eye disease factor". Vitamin A deficiency is one of the four major nutritional deficiencies recognized by the World Health Organization, and severe vitamin A deficiency can lead to night blindness.
What are the functions of vitamin A?
1) Eyes and Vitamin A
Why are some people's eyes unable to adapt to changes in light when we enter places with dim lighting such as cinemas? (Photophobia) is due to a lack of vitamin A. Vitamin A is a component of visual pigments in the eyes, especially the pigments that sense low light, which are essential for synthesizing rhodopsin. Once vitamin A deficiency occurs, the synthesis of rhodopsin decreases, leading to a decrease in our adaptability when transitioning from bright to dark areas. It takes longer than the average person to see things clearly. If vitamin A deficiency continues, the symptoms will gradually worsen, ultimately leading to "night blindness" where patients cannot see clearly in the evening or at night. Vitamin A can also prevent dryness of the conjunctiva and cornea, protecting visual health.
2) Vitamin A helps maintain skin and mucosal health
Beautiful and smooth skin, moisturized and shiny hair, and healthy and shiny nails all rely on sufficient supply of vitamin A. Vitamin A can induce epithelial cell differentiation and proliferation, and under normal supply of vitamin A, the epidermis does not undergo keratinization. Vitamin A deficiency can also cause damage to the skin and mucous membranes, manifested as thickening of the skin (dryness, desquamation, and follicular keratinization such as papules), especially on the outer side of the upper arm and lower limb, with noticeable follicular keratinization and the appearance of some "unsightly small bumps" (perifollicular keratinization).
3) Vitamin A enhances immunity
When air or food enters our mouth, nose, lungs, and gastrointestinal tract, it comes into contact with epithelial cells on the mucosa (air pollution). What do epithelial cells do? It is a barrier for the human body to block the invasion of pathogens. Vitamin A can induce epithelial cell differentiation and proliferation. That is to say, vitamin A can promote the normal growth of the barrier against bacteria, so vitamin A can enhance the immune system of diseases such as colds. Lack of vitamin A in the respiratory epithelium can lead to keratinization, loss of cilia, and decreased resistance. The trachea and bronchi are susceptible to infection, and the body's ability to defend against bacteria decreases. This can lead to recurrent colds in young children, and in severe cases, even bronchopneumonia.
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