The role of vitamin A is to promote development and protect vision

Vitamin A has many functions. It can maintain our eyesight and promote the healthy development of bones. Especially now, babies should supplement some vitamin A appropriately. They can eat more carrots and foods rich in carotene.

1. Maintain normal visual function.

The eye's photoreceptors are the rods and cones in the retina. Both types of cells contain photosensitive pigments, namely rhodopsin, which is sensitive to weak light, and rhodopsin, which is sensitive to strong light. Both rhodopsin and rhodopsin are composed of opsin and retinal. When rhodopsin is exposed to light, 11-cis-retinal is isomerizes into trans-retinal and separates from the visual protein, causing it to lose its color. This process is called "bleaching". If you enter a dark place, you will not be able to see things because the rhodopsin, which is insensitive to weak light, disappears.

The separated retinal is reduced to all-trans retinal, which is further converted to trans retinyl ester (or isomerized to cis) and stored in the pigment epithelium. Retinyl ester hydrolases in the retina convert retinyl esters into trans-retinol, which is then oxidized and isomerized to form 11-cis-retinal. It then recombine with protein to form rhodopsin, restoring sensitivity to weak light, allowing one to see objects in a dark place at a certain illumination intensity. This process is called dark adaptation.

2. Maintain the health of epithelial tissue cells and promote the synthesis of immunoglobulins.

Vitamin A can participate in the synthesis of glycoproteins, which is very important for the normal formation, development and maintenance of the epithelium. When vitamin A is insufficient or deficient, it can lead to abnormalities in glycoprotein synthesis intermediates and the accumulation of low molecular weight polysaccharides-lipids, causing hyperplasia and thickening of the epithelial basal layer, accelerated cell division, increased synthesis of tension fibrils, and changes in the surface layer such as flattening, irregularity, and drying of cells.

3. Maintain normal bone growth and development.

Vitamin A promotes protein biosynthesis and bone cell differentiation. When it is deficient, the balance between osteoblasts and osteoclasts is disrupted, resulting in either excessive bone proliferation due to enhanced osteogenic activity or non-absorption of already formed bone. If pregnant women lack vitamin A, it will directly affect the development of the fetus and even cause death.

4. Promote growth and reproduction.

Vitamin A helps in cell proliferation and growth. When animals lack vitamin A, they show obvious growth stagnation, which may be related to the animals' reduced appetite and decreased protein utilization. When vitamin A is deficient, it affects the production of spermatocytes in the spermatic epithelium of male animals, causes changes in the cycle of the vaginal epithelium in females, and also affects the placental epithelium, thereby hindering embryo formation. Vitamin A deficiency also causes a decrease in the activity of enzymes required to catalyze the formation of progesterone precursors, thereby reducing the production of steroids in the adrenal glands, gonads, and placenta, which may be the reason for affecting reproductive function.