Vitamin A Functions 1. Maintaining Vision Vitamin A promotes the formation of photoreceptor pigments in visual cells. All-trans retinaldehyde can be catalyzed by retinaldehyde isomerase to 4-cis-retinaldehyde, 4-cis-retinaldehyde can be combined with retinal protein to become retinal. After exposure to light, 4-cis-retinaldehyde becomes all-trans-retinaldehyde, which causes stimulation of the optic nerve and triggers vision because of the change in conformation. When exposed to light, retinaldehyde is destabilized and rapidly breaks down into retinoids and all-antiretinaldehyde, restarting the cycle. Vitamin A can debug the ability of the eyes to adapt to the intensity of external light to reduce the occurrence of night blindness and vision loss, to maintain a normal visual response, to help a variety of eye diseases (such as dry eye and conjunctivitis, etc. treatment). Vitamin A's role in vision was the first to be discovered and is also the most widely understood function. 2. Promotes growth and development Related to gene regulation by retinol. Retinol also has an effect equivalent to that of steroid hormones, which can promote the synthesis of glycoproteins. It promotes growth and development, strengthens bones, and maintains the health of hair, teeth and dentition. 3. Maintaining the integrity and soundness of epithelial structure Retinol and retinoic acid can regulate gene expression, attenuate the differentiation of epithelial cells to squamous and increase the number of epithelial growth factor receptors. Therefore, vitamin A can regulate the growth of epithelial tissue cells and maintain the normal form and function of epithelial tissue. Keep the skin moist, prevent the skin mucosa dry keratinization, less susceptible to bacterial damage, help on acne, pustules, boils, skin surface ulcers and other conditions of the treatment; help to get rid of age spots; can maintain the health of the surface layer of tissues or organs. 4. Strengthen the immune system Vitamin A helps to maintain the normal function of the immune system, can strengthen the resistance to infectious diseases, especially respiratory infections and parasitic infections; help in the treatment of emphysema, hyperthyroidism. 5. Remove free radicals Vitamin A also has a certain antioxidant effect, can neutralize the harmful free radicals. Vitamin A Side Effects Vitamin A Functions 1. Maintaining Vision Vitamin A promotes the formation of photoreceptor pigments in visual cells. All-trans retinaldehyde can be catalyzed by retinaldehyde isomerase to 4-cis-retinaldehyde, 4-cis-retinaldehyde can be combined with retinal protein to become retinal. After exposure to light, 4-cis-retinaldehyde becomes all-trans-retinaldehyde, which causes stimulation of the optic nerve and triggers vision because of the change in conformation. When exposed to light, retinaldehyde is destabilized and rapidly breaks down into retinoids and all-antiretinaldehyde, restarting the cycle. Vitamin A can debug the ability of the eyes to adapt to the intensity of external light to reduce the occurrence of night blindness and vision loss, to maintain a normal visual response, and help to a variety of eye diseases (such as dry eye and conjunctivitis, etc. treatment). Vitamin A's role in vision was the first to be discovered and is also the most widely understood function. 2. Promotes growth and development Related to gene regulation by retinol. Retinol also has an effect equivalent to that of steroid hormones, which can promote the synthesis of glycoproteins. It promotes growth and development, strengthens bones, and maintains the health of hair, teeth and dentition. 3. Maintaining the integrity and soundness of epithelial structure Retinol and retinoic acid can regulate gene expression, attenuate the differentiation of epithelial cells to squamous and increase the number of epithelial growth factor receptors. Therefore, vitamin A can regulate the growth of epithelial tissue cells and maintain the normal form and function of epithelial tissue. It keeps the skin moist, prevents dry keratinization of the skin mucosa, is less susceptible to bacterial damage, and helps in the treatment of acne, pustules, boils, and ulcers on the surface of the skin; helps to get rid of age spots; and can maintain the health of the surface layer of tissues or organs. Lack of vitamin A will reduce the function of epithelial cells, resulting in decreased skin elasticity, dryness and roughness, and loss of luster. 4. Strengthen the immune ability Vitamin A helps to maintain the normal function of the immune system, can strengthen the body's resistance to infectious diseases, especially respiratory infections and parasitic infections; help to emphysema, hyperthyroidism treatment. 5. Remove free radicals Vitamin A also has a certain antioxidant effect, can neutralize the harmful free radicals. Vitamin A side effects 1, acute vitamin A poisoning: adults a dose of more than 90 ~ 300mg (30 ~ 1 million IU), children a dose of more than 90mg (300,000 IU) can be an acute poisoning, the main manifestations of drowsiness or over-excitement, headache, vomiting and other symptoms of high cranial pressure, 12 ~ 20 hours after the appearance of skin redness and swelling, followed by peeling, to the palms of the hands, soles of the feet, and other thick places the most obvious, a few weeks before recovery. The skin becomes red and swollen after 12 to 20 hours, followed by peeling of the skin, most obvious on the palms of the hands, soles of the feet and other thick places. In infants and young children, high cranial pressure is the main feature, and bulging fontanel can be seen in those with unclosed fontanel. Cerebrospinal fluid is characterized by increased pressure, normal cell count, low protein, and normal sugar. Plasma vitamin A level increases dramatically, up to 500μg/L or more (200μg/L in normal adults). 2、Chronic vitamin A poisoning: adults ingest 24～30mg (8～100,000IU) per day for half a year; or 9～12mg (3～40,000IU) per day for more than 8 years can cause chronic poisoning. Infants and young children ingesting 15-30mg (50-100,000IU) per day for more than 6 months can cause chronic poisoning. The main manifestations are loss of appetite, weight loss, followed by dry skin, flaking, cracking, dry hair, alopecia, gums red and swollen, dry and cracked lips and nose bleeding and other skin and mucous membrane damage, as well as long bones and muscle joints pain with swelling, physical examination can be seen anemia, spleen enlargement.

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