VITAMIN A

Vitamin A or retinol is a fat-soluble vitamin. It is very important for vision, immune system, skin and growth. It is only present in animal fats while few carotenes in plant foods (especially beta-carotene) act as pro-vitamin A and some part of these carotenes can be converted into Vitamin A by lever. 

Importance for Health

Vitamin A is especially important for vision. It is needed by retina to form retinal pigments which prevents night blindness. Retina of eye is necessary for both colour vision and low light.

It is also important for skin as it reduces dryness of skin by the growth of mucus-secreting cells and also down-regulate production of sebum. It can also treat and reverse skin problems like photodamage (sun-damaged skin), cellulite and striae (stretch marks).

Vitamin A is also important for immune system. It is helpful in maintaining immune systems including macrophages, neutrophils, lymphocytes etc.

Vitamin A is beneficial for human growth hormone which is important for growth of body cells.

It is also necessary for production of blood cells.

Deficiency Symptoms

·         Night blindness is the earliest sign of Vitamin A deficiency. Persistent and severe deficiency produces xerophthalmia (eye dryness) due to atrophy of mucus-secreting cells which can lead to total blindness.

·         Lack of immunity can lead to ear infection, urinary tract infection and several other infections.

·         Dryness of skin and acne.

·         Impairment of growth of body cells including skeletal growth.

·         Enamel hypoplasia (thinning and deficiency of teeth enamel).

·         Reproductive problems in both males and females. In males, it is due to atrophy of testes germinal epithelium while due to interruption of sexual cycle in females. 

Daily Requirement

The daily requirement of Vitamin A differs with age, sex and other factors. RDA (recommended daily intake) for men between 19 and 70 years of age is 900 micro-grams while for the women of same age is 700 micro-grams. Upper limit for both male and female is 3000 micro-grams. RDA is slightly higher than minimum requirement. 

Food Sources

Carrots are main plant source of Vitamin A

Vitamin A is directly present in animal foods and indirectly in plant foods (as pro-vitamin A carotenes). Foods with higher amount are given below. It is given as their quantity per 100 grams and percentage according to RDA of men.

·         Liver (beef, fish) > (6500 micro-grams, 722%)

·         Liver (chicken) > (3296 micro-grams, 366%)

·         Carrot > (835 micro-grams, 93%)

·         Sweet Potato (raw) > (709 micro-grams, 89%)

·         Butter > (684 micro-grams, 76%)

·         Spinach > (469 micro-grams, 52%)

·         Pumpkin > (400 micro-grams, 41%)

·         Cheddar Cheese > (256 micro-grams, 29%)

·         Egg > (140 micro-grams, 16%)

·         Apricot > (96 micro-grams, 11%)

These values are according to USDA. 

Problems with Higher Intake

Vitamin A can be dangerous if taken in amount greater than tolerable upper limit (3000 micro-grams for most men and women). The condition is known as Hypervitaminosis A. Its symptoms include softening of skull bone, blurred vision, decreased appetite, headache, drowsiness, nausea, hair loss etc.

This condition can be treated by avoiding high intake of Vitamin A.