The health benefits of Vitamin A
Vitamins can be defined as essential organic compounds required in very small amounts that are involved in fundamental functions of the body, such as growth, maintenance of health, and metabolism. All vitamins are generally classified as water soluble and fat soluble vitamins. Vitamin A is a member of four fat soluble vitamins, A, E, D, and K. Vitamin A is actually a family of fat-soluble vitamins such as retinol, which is considered the most active form of vitamin A.
The vitamin A of origin from animal products is referred to as preformed vitamin A and is found in foods such as liver, egg yolk, butter, whole milk products, and fish liver oils.
The vitamin A of origin from plants is called provitamin A. Carotenoids, the red, orange, and yellow pigments are synthesized by a wide variety of plants including carrots and other vegetables including: Raw spinach, cantaloupe, tomatoes, sweet potatoes, papayas, apricots, romaine lettuce. Vitamin A is involved in many important body functions in addition to helping with vision.
Health benefit to vision
Vitamin A is required in the production of rhodopsin, the visual pigment used in low light levels. Vitamin A improves our vision and prevents night blindness.
Maintaining epithelial cell's structure and function
Vitamin A affects gene expression and thus controlling cell development. Epithelial cells of the lungs, trachea, skin, and gastrointestinal tract need vitamin A to maintain their normal structure and functions. Vitamin A directs the differentiation of keratinocytes (immature skin cells) into mature epidermal cells. Vitamin A also directs the synthesis of keratins, with genes for small keratin molecules transcribed and translated.
Functions in growth
Vitamin A promotes growth through stimulating the growth of epithelial cells and other possible mechanism such as increasing the synthesis of cell surface components. One important member of these components is glycoprotein which is needed for important cell-to-cell connections. Vitamin A can modify cell surfaces through increasing glycoprotein synthesis at the gene level or by improving attachment of glycoproteins to cell surfaces to induce cell adhesion.
Participating in cell surface functions
One of vitamin A's cell surface functions is mediated through glycoprotein. Glycoprotein is a principal cell surface component involved in many cell surface functions such as cell communication, cell recognition, cell adhesion, and cell aggregation.
Acting as antioxidants
Carotenoids are powerful antioxidants that protect the body's cells from damage caused by pollution, aging and other factors. They also prevent cardiovascular diseases by protecting low-density lipoproteins from oxidation sand protecting eye health.
Vitamin A makes immune system healthy and strong. It is needed for T-lymphocyte function and for antibody response to viral parasitic, and bacterial infections. Natural killer cell activity and phagocytosis are also impaired with vitamin A deficiency. Bone development and maintenance also needs vitamin A. Vitamin A deficiency results in excessive deposition of bone.
Vitamin A deficiency is less common in the United States than in developing countries where inadequate is common in children under 5 years old. Deficiency symptoms include anorexia, retarded growth, increased susceptibility to infections, obstruction and enlargement of hair follicles, and keratinization of epithelial (mucous)cells of the skin with failure of normal differentiation, night blindness, and abnormal changes in conjunctiva and cornea of the eyes. Some conditions and populations may need more vitamin A. For example, people who have absorptive disorders such as those with steatorrhea, pancreatic liver, or gallbladder diseases. People who have chronic nephritis, acute protein deficiency, intestinal parasites, or acute infections may also need more vitamin A intake.
As discussed above, vitamin A is needed to maintain many important body functions. Although deficiency is not very common in the United States, under some special health conditions or with different populations, we need to pay attention to these people's requirement for vitamin A.