Vitamin A, role on eye, role on immunity, role on skin, role on reproduction, antioxidant activity and anticarcinogenic activity

Description :   Vitamin A is a fat soluble vitamin, naturally found in many foods. It plays various important roles

Article Details    :

Vitamin A is a fat soluble vitamin, naturally found in many foods. It plays various important roles in body and most significantly promotes vision, reproductive health and immune system.

Chemistry

• Basically the term Vitamin A is collectively used for representing various biologically active and structurally relative molecules
• The natural and synthetic forms of Vitamin A is generally known as retinoids
• Retinol, retinal and retinoic acid are known as the vitamers of Vitamin A
• Retinol is a primary alcohol that contains a beta-ionone ring in its structure
• Retinal is an aldehyde generally derived by the oxidation of retinol and retinoic acid is obtained by the oxidation of retinal

Carotenoids

• Carotenoids are the provitamins of Vitamin A
• Carotinoids are basically of three types like alpha carotene, beta carotene and beta cryptoxanthin, among these beta carotene is considered as the most important carotinoid
• Carotenoids are converted into Vitamin A in body

Absorption, transport as well as mobilization of Vitamin A

• Dietary retinyl esters are hydrolyzed with the help of the enzyme hydrolase in intestine and subsequently releases retinol as well as free fatty acids
• Carotenes are also hydrolyzed in intestine and release retinal, which is then converted into retinol
• Retinol is then reesterified into long chain fatty acids and incorporated into chylomicrons and then transported into the lymph, which is then taken up by liver and stored there
• As per the need of the body Vitamin A is released from the liver as free retinol and then it is transported in circulation by binding with a protein named retinol binding protein (RBP)
• This retinol-RBP complex then binds to the specific receptor present in cell membrane and enters into the cell through it and performs its functions

Sources

Vitamin A is widely present in both plant and animal sources. Foods, which are rich in Vitamin A are listed below –

• Egg especially egg yolk
• Beef liver
• Oily fish
• Fish liver oil
• Cheese
• Yogurt
• Milk
• Carrot
• Spinach
• Sweet potatoes
• Pumpkin
• Mangos
• Apricot
• Black eyed peas
• Tomato juice
• Broccoli
• Pistachio nuts
• Butter

Supplements

• Apart from dietary source Vitamin A is also available in the form of supplements
• It is also available in the form of retinyl palmitate or retinyl acetate
• It has seen that Vitamin A is present in some supplements as beta-carotene and some supplements also contain preformed Vitamin A
• Though one can consume Vitamin A through supplements but it is always better to consume Vitamin A from natural sources

Health benefits

Role on eye

• Vitamin A plays significant role in promoting eye health and vision
• It helps to improve the health of conjunctiva as well as cornea and protects them from oxidative damages
• We know that retina of an eye contains two type of cells called rod cell and cone cell. Rod cells are generally located at the periphery of the retina whereas cone cells are located at the centre
• Cone cells help in colour vision and bright light vision but rod cells are involved in dim light vision
• Rod cells contain a pigment named rhodopsin, which helps in dim light vision and Vitamin A helps in the synthesis of rhodopsin thus deficiency of Vitamin A decreases the production of rhodopsin and impaired dim light vision. Thus individual with Vitamin A deficiency cannot view properly in dim light or night and this condition is known as night blindness. Consumption of Vitamin A rich diet is considered as one of the most significant options for preventing night blindness

Anti-carcinogenic activity

• It has seen that consumption of Vitamin A especially in the form of beta carotene significantly decreases the prevalence of certain type of cancers
• Its antioxidant activity is responsible for reducing oxidative stress in body, which ultimately decreases the risk of cancers
• It is also associated with hindering the growth of malignant cells
• It is very effective for decreasing the prevalence of cervical cancer, bladder cancer and lung cancer

Role on reproductive system

• It plays imperative role in maintaining a healthy reproductive system for both genders
• It also helps in the normal growth and development of embryo during gestational period
• It also helps to improve the quality of sperm
• It helps to promote spermatogenesis too and also plays vital role in maintaining the male genital tract
• It has seen that deficiency of Vitamin A among women is    Read more