Vitamin A : Source, Benefits, Daily Allowance And Toxicity

Vitamin A: Vitamin A is a group of compounds that includes retinol, retinal, retinoic acid, beta-carotene. Vitamin A is involved in vision, immune function, reproduction, and cellular transmission. Vitamin A is significant for vision as an essential component of rhodopsin, a protein that senses light in the retinal receptors, and because it helps the normal differentiation and functioning of the conjunctival membranes and the cornea.

Vitamin A further supports cell growth and differentiation, playing a significant role in the normal formation and maintenance of the heart, kidneys, lungs, and other organs.

Vitamin A found in two main forms in foods:

• Retinol, the sort of vitamin A absorbed while eating animal food sources, is yellow and it is a fat-soluble substance. For the pure alcohol form is unstable, the vitamin is observed in tissues in a form of retinyl ester. It is further commercially produced and served as esters such as retinyl acetate or palmitate.
• The carotenes alpha-carotene, gamma-carotene, beta-carotene; and the xanthophyll beta-cryptoxanthin (all contain beta-ionone rings), but no other carotenoids, role as provitamin A in herbivores and omnivore animals, which hold the enzyme beta-carotene 15,15′-dioxygenase which adheres beta-carotene in the intestinal mucosa and transforms it to retinol.

Vitamin A Recommended Daily Intake

Vitamin a recommended daily intake and other nutrients are provided in the Dietary Reference Intakes (DRIs) formed by the Food and Nutrition Board at the Institute of Medicine of the National Academies.

• Infants (0-12months) -> 400-500 mg/day
• Children (1-8 years) -> 300-400 mg/day
• Male -> 900 mg/day
• Female -> 700 mg/day
• Pregnancy -> 750-770 mg/day
• Lactation -> 1200-1300 mg/day

Importance of vitamin A

1. Vitamin A is important for growth and development.
2. It is important for maintaining the immune system.
3. It is needed for the retina to produce “Rhodopsin” the light absorbing molecule to have both low-light and color vision.
4. It is important for the growth factor of the epithelial cell.

Vitamin A for Pregnancy
Vitamin A is necessary for immune function, visual health, and fetal growth and development. Vitamin A insufficiency is a public health problem in many parts of the world, especially Africa and South-East Asia. It can make visual impairment in the sort of night blindness in children, may raise the risk of illness and death from childhood infections, including measles and causing diarrhea.

Although pregnant women are sensitive to vitamin A deficiency during gestation, perceptivity is at its highest during the third trimester of pregnancy due to quickened fetal development and the physiological rise in blood volume during this period.

While there is some suggestion that low dosages of vitamin A supplements supplied to pregnant women on a daily or weekly basis, beginning in the second or third trimester, can decrease the severity of decline in maternal serum retinol levels throughout late pregnancy and the symptoms of night blindness, current evidence intimates that vitamin A supplementation during pregnancy does not lessen the risk of illness or death in mothers or their infants.

Vitamin A for pregnancy should be inspired to get adequate nutrition, which is best gained through the consumption of a healthy balanced diet.

Vitamin A Benefits for Skin

Most of the vitamin A intake gets from eating foods rich in beta-carotene and provitamin A carotenoids, that are potent antioxidants. Not just do these squelch free radicals that more break down collagen and contribute to fine outlines and saggy skin, they more lessen skin’s sensitivity to the sun, giving some natural protection against sun-induced redness and pigmentation.

Retinal, retinol and retinoic acid are significant to cell production and growth. Vitamin A benefits for skin similarly stimulates fibroblasts—the cells capable of developing tissue that prevents skin firm and healthy—in the deep layers of skin. Because vitamin A and carotenoids perform such a big role in cell and tissue growth, not getting enough can commence to weakened skin, causing problems varying from dryness to wounds that heal more slowly.

Vitamin a benefit for skin is an important part of the immune system; body’s bouncer—a first line of defense toward bacteria, pollutants, and infection. By raising cell production, vitamin A benefits to strengthen this barrier, protecting our complexion from harmful nuisances that attempt to tackle the surface.

Vitamin A Sources

• Vitamin A Animal source: – Cod liver oil, liver (beef, chicken, turkey), egg, butter, cheddar, small fish.
• Vitamin A Plant source: – Capsicum, sweet, potato, carrot, pumpkin, broccoli, kale, spinach, apricot, melons.

Deficiency

1. Nyctalopia (Night blindness).
2. Xeropthalmia
3. Keratomalacia
4. Follicular hyperkeratosis.

Toxicity (More than 4500 mg)

1. Carotenodermia (Yellow discoloration of skin)
2. Nausea, vomiting
3. Blurred vision
4. Anorexia, abdominal pain
5. Irritability, weakness
6. A headache, hair loss, muscle loss
7. Bone fractures
8. Dry skin, drying of the mucous membrane.