The physiological function of vitamin A

Dollar unsaturated alcohols, is a fat-soluble vitamins. As human beings or mammals, the lack of vitamin A in dry eye occurs when the vulnerable, it is also known as anti-alcohol dry eye. Vitamin A is known A1 and A2 are two kinds, A1 found in animal liver, blood and the retina in the eye, also known as retinol, natural vitamin A major in this form. A2 mainly in the liver of freshwater fish. A1 is a fat-soluble vitamin yellow flaky crystal, melting point 64 ℃, vitamin A2 melting point 17 ~ 19 ℃, usually a golden yellow oily. Vitamin A is a ring containing the β-Angelica-one multi-enol. The chemical structure of vitamin A2 and A1 the difference only in the β-Angelica-one ring more than one double bond in 3,4-position. Vitamin A molecules have unsaturated bonds, the chemical nature of the lively, easily oxidized in air, or by exposure to ultraviolet damage, loss of physiological function, so vitamin A, agents should be packed in dark brown bottles to save. Either A1 or A2, both with the role of antimony trichloride, showing the deep blue of this nature can be used as a basis for quantitative determination of vitamin A. Many plants such as carrots, tomatoes, green leafy vegetables, maize carotenoid-containing substances, such as α, β, γ-carotene, cryptoxanthin, lutein and so on. Some of carotenoids and vitamin A1 have the same ring structure, in the body can be transformed into vitamin A, it is known as the vitamin A of the original, β-carotene, vitamin A1 contains two ring structure, the conversion rate is highest. Part of β-carotene, plus two molecules of water can generate two molecules of vitamin A1. In animals, this process of water oxidation by β Hu Radka Su -15,15 '- dioxygenase catalysis, mainly in animals, within the small intestinal mucosa. Foods, or by β-carotene, vitamin A cracking generated in the small intestinal mucosa cells into the ester with the fatty acid-binding, and then mixed with chylomicrons, absorbed into the body through the lymphatic. Animals, the liver storage of vitamin A, for the main site. When the body is necessary, and then released into the blood. In the blood, retinol (R) and retinol-binding protein (RBP) and plasma albumin (PA) combined to produce R-RBP-PA complex and transit to various organizations.

It is the United States of America 1913 Davis chemist extracted from cod liver obtained. It is the yellow powder, insoluble in water, soluble in fats, oil, organic solvents. Chemical properties of relatively stable, but prone to UV damage, should be stored in brown bottle. Vitamin A is the rhodopsin in the eye of raw materials, but also the skin necessary materials, were the lack of it will get dry eye, night blindness and so on.

Physiological function of vitamin A, vitamin A is a complex organism as a necessary nutrients, in different ways it affects almost all body tissues. Although the vitamin is first discovered, but about its physiological function has Shangmo fully opened.

Vitamin A is a complex organism as a necessary nutrients, in different ways it affects almost all body tissues. Although the vitamin is first discovered, but about its physiological function has Shangmo fully opened. On the current state of knowledge in terms of vitamin A (including carotenoids) is the most important physiological functions, including

1. To maintain the visual

Vitamin A can promote the visual cells photosensitive pigment formation. All-trans-retinaldehyde retinaldehyde isomerase can be catalysts for the 4 - cis - retinoic aldehyde, 4 - cis - retinal opsin can be integrated into rhodopsin (rhodopsin). Rhodopsin light after the event in which 4 - cis - retinaldehyde into all-trans retinaldehyde, as conformation changes, caused by stimulation of the optic nerve, triggering the visual. The case of rhodopsin after light unstable and rapidly broken down into opsin and all-trans retinal, re-start the entire cycle. Vitamin A can be to debug the eyes adapt to light the strength of the ability to reduce the incidence of night blindness and vision loss and maintain a normal visual response, which contributes a variety of eye diseases (such as dry eye and conjunctivitis treatment). The role of vitamin A for vision was first discovered, and it is understood most functions.

2. To promote the growth and development

With retinol regulation of genes related to. Retinol also have the equivalent of the role of steroid hormones could promote the synthesis of glycoproteins. To promote growth, development, strong bones, maintaining hair, teeth and gums healthy.

3. To maintain the integrity of epithelial structure and integrity

Retinol to retinoic acid regulation of gene expression, decreased epithelial cell differentiation of the scaly, increasing the number of epidermal growth factor receptor. Thus, vitamin A can regulate the growth of epithelial cells to maintain the normal epithelial tissue morphology and function. To keep their skin moist, preventing dry skin and mucous membrane keratinization, less susceptible to bacterial injury, contribute to the acne, pustule, boil sores, the treatment of skin ulcers embolism; help dispel senile plaque; able to maintain the health of tissue or organ surface. A lack of vitamin A, would epithelial cells dysfunction, leading to decreased skin elasticity, dry and rough and dull.

4. To enhance immunity

Vitamin A helps to maintain the normal function of the immune system, can enhance infectious diseases, especially respiratory infections and parasitic infections of the body resistance; contribute to the emphysema, the treatment of hyperthyroidism.

5. Free Radical Scavenging

Vitamin A also has a certain antioxidant can neutralize harmful free radicals.

In addition, many studies have shown that skin cancer, lung cancer, throat cancer, bladder cancer and esophageal cancer are related to intake of vitamin A-related; However, these clinical studies remain to be further confirmed by its reliability.

The daily demand:

Normal adult daily requirement of vitamin A minimum of about 3500 international units (0.3 micrograms of vitamin A or vitamin A is equivalent to 0.332 mg acetyl-1 international units), children of about 2000 ~ 2500 international units, not intake too much. In recent years, the study shows that it also has anti-cancer effects. Vitamin A in animal liver contains a particularly large number, followed by butter and eggs and so on.

Women need 0.8 mg. Eel 65 grams or 80 grams chicken livers, 75 g carrot, 125 grams or 200 grams of Brassica crispa tuna.

Efficacy: enhancing the immune system and help cell regeneration and protect cells from free radicals can cause many diseases of the violation. It enables the respiratory tract, mouth, stomach and intestinal mucosa and other organs from damage, vitamin A can be eyesight.

Side effects: a daily intake of 3 mg of vitamin A, have led to the risk of osteoporosis. The long-term daily intake of greater than 3 mg of vitamin A cause loss of appetite, dry skin, hair loss, bone and joint pain, and even causing a miscarriage.