Vitamin A has a variety of physiological functions, is necessary for vision, growth, epithelial tissue and bone development, spermatogenesis and fetal growth and development. And for the mother-to-be, the need for vitamin A has increased by nearly 25% compared to the pre-pregnancy period. The concentration of vitamin A in the mother's blood decreases in the early stages of pregnancy, rises in the late stages, decreases when labor is imminent, and then rises again after delivery, so proper supplementation of vitamin A is necessary for the mother-to-be.

However, because large doses of vitamin A are toxic to the human body, and vitamin A are able to pass through the placental barrier smoothly and thus, the mother-to-be supplemented with vitamin A dose can not be too large, a large amount of vitamin A is not only unfavorable to the mother's body, but also affects the growth and development of the fetus. For mothers-to-be, symptoms of acute vitamin A toxicity include lethargy, headache, vomiting, and optic papillary edema. Chronic vitamin A overload can manifest as dry, rough skin, hair loss, dry and cracked lips, itchy skin or low-grade fever.

For the little baby in the abdomen, if the mother-to-be in early pregnancy a large number of vitamin A, the fetus will be in accordance with the organ formation of the smooth, the occurrence of anencephaly, eye defects, cleft palate, spina bifida, limb defects and other malformations. Mothers-to-be in large quantities can cause fetal urinary tract malformations as well as the occurrence of congenital cataracts.

In view of the fact that a large amount of vitamin A can cause toxic effects to the mother-to-be and the fetus, it is generally believed that the dose of vitamin A supplements should not be higher than 1.5 times the RDA (Recommended Dietary Allowance for Nutrients), i.e., 4,000 IU. However, at present, there are more pregnancy supplements with added vitamin A, and the accumulation of vitamin A may result in the disadvantage to the mother-to-be and the fetus.

Like vitamin A, beta-carotene passes through the placental barrier and can be converted into vitamin A under the action of carotenoid enzymes in the liver and intestinal wall of the human body and has the same physiological effect as vitamin A.

Beta-carotene can be converted into vitamin A under the action of carotenoid enzymes in the liver and intestinal wall of the human body, and has the same physiological effect as vitamin A. Since the conversion of beta-carotene to vitamin A in the body is flexibly regulated by a variety of factors and does not overproduce vitamin A, beta-carotene does not have the potential toxicity of vitamin A alcohol. Although, very large doses of β-carotene can cause β-carotenemia, resulting in yellowing of the skin, it is sufficient to discontinue the use of β-carotene, which has no toxic effect on the human body. Compared to vitamin A, beta-carotene is much safer.

Chondroitin sulfate is a sticky polysaccharide that requires a large amount of vitamin A for its synthesis. Vitamin A deficiency naturally leads to a decline in chondroitin sulfate synthesis, and the health of the skin can suffer.

In fact, whether the skin aging caused by vitamin A deficiency or normal physiological process of skin aging, are related to the weakening of chondroitin sulfate synthesis ability, so vitamin A deficiency can accelerate skin aging.

Vitamin A is also the thalamus, pituitary gland and other important endocrine hormone nutrients. When it is insufficient, can not ovaries send normal secretion of hormones instructions, resulting in low ovarian function, the relative increase in male hormones, the skin is prone to acne, affecting the beauty of the skin.

Utility

Preventing night blindness and vision loss, helps in the treatment of a variety of eye diseases (Vitamin A promotes the formation of photoreceptor pigments in the eye);

Anti-respiratory infections;

Contributes to the normal functioning of the immune system;

Can be used to make an early recovery from an illness;

It can maintain the health of tissues or the surface layer of the organs.

Helps to get rid of age spots;

Promotes development, strengthens bones, and maintains the health of the skin, hair, teeth, and dental bed;

Externally, it helps in the treatment of acne, pustules, boils, and ulcers on the surface of the skin;

Helps in the treatment of emphysema and hyperthyroidism.

Deficiency

1, the decline in dark adaptation, night blindness and dry eye disease

The earliest symptom of Vit A deficiency is the decline in dark adaptation, and in severe cases, it can lead to night blindness, that is, the inability to see clearly in the dark light. Due to degenerative changes in the cornea, conjunctiva tissues, and lacrimal gland, a series of changes such as dryness, inflammation, softening, ulceration, and keratinization of the cornea can occur, resulting in the appearance of vesicular silver-gray spots on the conjunctiva. Severe corneal manipulation can often lead to irreversible blindness.

2, mucous membrane, epithelial changes

epithelial tissue is poorly differentiated, the skin, especially the arm, leg, shoulder, lower abdomen, skin roughness, dry, scaly state and other keratinization changes. Oral cavity, digestive tract, respiratory tract and the mucous membrane of the genitourinary tract pushed to moisturize, softness, so that bacteria are easy to invade, especially in the swineherd prone to bronchopneumonia and other serious diseases.

3, growth and development is impeded

Especially in children, the first impact on bone development, gingival hyperplasia and keratinization, affecting the development of tooth enamel cells, so that the teeth to stop growing

4, the other

Taste, smell weakened, decreased appetite.

Foods rich in vitamin A

Carrots, yellow and green vegetables, eggs, yellow fruits, spinach, pea shoots, sweet potatoes with red hearts, green peppers, cod liver oil, animal liver, milk, dairy products, cream.