Wednesday, 2 July 2014

Vitamin A

Vitamin A (retinol) is a fat soluble vitamin which is made by combination of group of nutritionally unsaturated hydrocarbons. The groups of hydrocarbons which form vitamin A consist of retinoic acid, retinol; retinal provitamin A carotenoids out of all these beta carotene plays a very important role in various functions of body.

Two forms in which vitamin A is present in food contents are as follows

• Retinol (a yellow colored fat soluble substance) one of the forms of vitamin A is absorbed from eating animal food. This form is unstable and that’s why present in the tissues of animals in the form of retinyl ester.
Commercially this retinyl ester is administered in the form of retinyl acetate or palmitate.

• Second form in which vitamin A is available in food sources is carotenes.  There are different forms of carotene present in food source examples are alpha- carotene, beta- carotene, gamma- carotene, xanthophyll beta- cryptoxanthin.
Herbivores and omnivore animals possess an enzyme in the intestinal tract which helps to break down beta-carotene into retinol.
Carrot is a rich source of vitamin A

FUNCTIONS OF VITAMIN A

Vitamin A plays a very important role in maintaining many functions of body which are as follows
• Plays a very important role in vision.
• Helpful in maintaining bone metabolism.
• Haematopoiesis.
• Helps in developing healthy immune system.
• Helps in maintaining healthy skin, teeth, skeletal soft tissue and mucus membranes.
• Helps to protect cells from damage by free radicals.
• Plays important role in development of embryo and reproduction process.
• Have an antioxidant property.
• Food containing beta carotenes help to reduce the risk of cancer.
•  Act as an anti aging component of diet. People who take diet rich in vitamin A show less signs of aging like wrinkles of face, dryness of skin, lack of glow of face.

NORMAL VALUES

Recommended daily intake of vitamin A for different age groups is as follows
For infants (average intake)
0-6 months: 400 micrograms per day (mcg/day)
7 months to 1 year: 500 mcg/day
In cases of children
• 1-3 years: 300 mcg/day
• 4-8 years: 400 mcg/day
• 9-13 years: 600 mcg/day
In adults recommended daily intake is as follows
• In cases of females age 14 and above: 700 mcg/day
• In cases of males  age 14 and above: 900 mcg/day

AGE AND SEX

More commonly affected age group with the deficiency of vitamin age is children below the age of 5 years.

RACE

Vitamin A deficiency affect most commonly people of Southeast Asia and Africa.

DEFICIENCY OF vitamin A

Deficiency of vitamin A occurs where individuals do not consume adequate diet containing carotenoids such as animal and dairy products.
In cases of infants where weaning is started at very early time and mother’s milk is left is on higher risk for vitamin A deficiency.
Other derangements due to which vitamin A deficiency occurs are as follows
• Long history of mal absorption of fat.
• Impairment in the formation of bile juice by gall bladder and release of it.
• As vitamin A is a fat soluble vitamin so decrease in amount of fat in intestines lead to decrease in absorption of vitamin A in the body.
Deficiency of zinc in diet also leads to impairment of absorption of vitamin A, its metabolism, and transport.

Deficiency of vitamin A leads to following conditions

• Night blindness; impaired vision especially at night.
• Xerophthalmia
• There happens dryness of conjunctiva known as xerosis, and then there appear small plaques in eyes known as Bitot’s spots.
• Due to impairment of immune system of body infections increase in ear and urinary tract infections.
• If its supply is decreased in pregnant females then there occurs decrease in fetal development and also in breast milk of mother.

SOURCES OF vitamin A

• Spinach high content of carotene is present in it.
• Liver( beef, fish, pork )
• Cod liver oil.
• Carrot, broccoli.
• Butter.
• Potato especially sweet potato.
• Fruits like papaya, mango (papaya not to be taken in pregnancy can lead to abortion )
• Cantaloupe melon is a rich source.
• Pumpkin, peas, tomatoes.
• Collard greens, dandelion greens.
• Milk, egg, apricot.

EXCESS OF vitamin A IS ALSO DANGEROUS

Excessive intake of vitamin A leads to following symptoms
• Nausea.
• Vomiting.
• Irritability.
• Appetite is decreased.
• Attacks of headache are recurrent.
• Vision is blurred.
• Excessive hair loss can occur.
• Pain in abdomen.
• Weakness and drowsiness.
• Altered mental state of health is present.
• Drying of skin and mucus membranes.
• Fever can also be a feature.
• Loss of sleep.
• Weight loss is present in chronic cases of toxicity.
• Increased risk of bone fractures.