The Harm of Vitamin A Deficiency
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The Harm of Vitamin A Deficiency

Views: 0     Author: Site Editor     Publish Time: 2022-12-02      Origin: Site

Vitamin A is a fat soluble vitamin, an organic compound, which is stable to heat, acid and alkali, and easy to be oxidized. Ultraviolet can promote its oxidative damage. Vitamin A includes A1 and A2, and A1 is retinol. Vitamin A2 is 3-dehydroretinol, and its physiological activity is 40% of vitamin A1.

Vitamin A has a variety of physiological functions, such as promoting growth and reproduction, maintaining normal secretion of bone, epithelial tissue, vision and mucosal epithelium. Vitamin A and its analogues have the effect of preventing precancerous lesions. In case of deficiency, it is manifested as growth retardation and dark adaptation decline, resulting in night blindness. Because the epithelial cells of epidermis and mucosa are dry, desquamate, hyperkeratosis, and lacrimal gland secretion is reduced, dry eye disease occurs, and the cornea is softened, perforated, and blind in severe cases. The epithelial cells of the respiratory tract become keratinized and lose their cilia, reducing their resistance to infection. The recommended vitamin A intake (RNI) for adults in China is 800 per day for males μ G retinol activity equivalent, 700 per day for women μ G retinol activity equivalent. The food with more vitamin A includes the liver, egg yolk and milk powder of poultry and livestock. The carotene can be changed into vitamin A in the intestinal mucosa, red yellow and dark green vegetables, and the fruit contains more carotene.

Vitamin A Powder Synthesis

Although vitamin A can be extracted from animal tissues, the resources are relatively dispersed, the steps are complex, and the cost is high. Therefore, commercial vitamin A is a chemical synthetic product. Industrial synthesis of vitamin A at home and abroad mainly includes Roche in Switzerland and BASF in Germany. The former uses β- Violenone is the starting material and characterized by Grignard reaction. After Darzens reaction, Grignard reaction, selective hydrogenation, hydroxyl bromination and dehydrobromination, vitamin A acetate is synthesized; The typical feature of the latter is Wittng reaction. Its synthesis route is shown in the figure "Synthesis of Vitamin A by BASF Method" β- Ionone is used as the starting material to generate acetylene through Grignard reaction with acetylene- β- Violet alcohol, selective hydrogenation to ethylene- β- Violet alcohol is condensed with C5 aldehyde to form vitamin A acetate with sodium alkoxide as catalyst after Wittng reaction.vitamin a powder for sale -herb-key

Vitamin A Application and Side Effects

Vitamin A is mainly used to prevent and treat night blindness and dry eye disease, as well as local suppurative infection of skin after burns. The intake of vitamin A by human body shall not exceed 3mg/day for adults and 2mg/day for children. If a large dose of vitamin A is taken, acute vitamin A excess will occur due to low excretion ratio. The main symptoms are short-term hydrocephalus and vomiting, and some may have headache, lethargy and nausea. After taking large doses of vitamin A for a long time, children will suffer from excessive vitamin A symptoms, mainly including hepatosplenomegaly, decreased red blood cells and white blood cells, excessive growth of bone marrow, brittle long bones, and fracture. A new Swedish study shows that middle-aged men with high concentrations of vitamin A in their blood are much more likely to have fractures in their old age than those with low levels of vitamin A. Therefore, vitamin A is indispensable to the human body and should not be abused. As long as food rich in vitamin A or carotene is guaranteed, vitamin A deficiency can be effectively prevented without taking additional vitamin A supplements.

The Dangers of Vitamin A Deficiency

Vitamin A deficiency has clinical and functional manifestations. Tolerance of primary vitamin A deficiency varies from person to person and depends on a number of geographic and epidemiological factors. The clinical manifestations of vitamin A deficiency are mainly ocular and visual and other symptoms and signs of epithelial dysfunction.

1. Eye and visual performance

Dry eye is one of the typical clinical features of vitamin A deficiency. According to specific ocular manifestations, dry eye can be divided into several stages. Stage XN is the earliest stage, mainly night blindness caused by impairment of dark adaptation function. Then there is the X1A stage, when the goblet cells secrete less mucus, resulting in dryness of the conjunctiva; then there is the X1B stage, when the vesicular Pitt's spots appear on the frontal surface of the conjunctiva. Stage X2 is the advanced stage of the disease, manifested as simple corneal dryness. When there is softening or ulceration of the cornea, or a liquefaction process of both, it is stage X3. At this time, if the liquefied surface is less than 1/3 of the corneal area, it is stage X3A, and if it is more than 1/3, it is stage X3B. Eyeball damage caused by corneal softening is called dry eye fundus disease, also known as stage XF.

2. Other manifestations of epithelial dysfunction

Thickening of the hair follicles (follicular keratinization) is a skin sign of vitamin A deficiency. Mucin production in the mucosa is reduced, and the morphology, structure, and function of the mucosa are abnormal, which can lead to pain and decreased mucosal barrier function, and can involve the throat, tonsils, bronchi, lungs, and digestive tract mucosa. Vitamin A deficiency and borderline deficiency lead to increased risk of infectious disease and mortality in children.

3. Abnormal Embryo Growth and Development

Vitamin A deficiency can impair embryonic growth. Experimental animals severely deficient in vitamin A often experience embryo resorption, and the surviving embryos also have abnormalities of the eyes, lungs, urinary tract, and cardiovascular system. When the human body is deficient in vitamin A, morphological abnormalities are less likely to occur, but abnormal lung functions can be seen.

4. Impaired immune function

Vitamin A deficiency can lead to the decrease of blood lymphocyte number, natural killer cells and specific antibody response. When vitamin A intake is insufficient, it can be observed that the number of white blood cells decreases, the weight of lymphoid organs decreases, the function of T cells is damaged, and the resistance to immunogenic tumors is reduced. In laboratory animal and human experiments, vitamin A deficiency leads to abnormal humoral and cellular immune functions.

5. The prevalence and mortality rate of infectious diseases increase

Vitamin A deficiency can lead to increased incidence rate and mortality of infectious diseases in laboratory animals and humans, especially in developing countries. Children with mild to moderate vitamin A deficiency have an increased risk of respiratory infections and diarrhea; The mortality rate of children with mild dry eye is four times that of children without dry eye. High dose vitamin A supplementation for hospitalized children with measles can significantly reduce the non mortality rate of children and reduce the severity of complications. Studies have shown that vitamin A supplementation can reduce the severity of diarrhea and malaria in young children.