Vitamin A is an important vitamin and I present to you evrything you should know about the essential constituent of the diet. Vitamin A is a complete group of unsaturated hydrocarbons comprising of retinol, retinoic acid, retinal and many provitamin A carotenoids. The most important carotenoid is the beta carotene. Vitamin A is also known by the name of Retinol because it produces the pigments in the retina of the eye. It is a fat soluble vitamin and is characterized into two types. One is the Preformed Vitamin A that is found in animal products like dairy products, fish, meat and the other type is pro-vitamin found in plant based products like fruits and vegetables.

The discovery of Vitamin A

It was in the year 1912 when Frederick Gowland Hopkins discovered that milk contained “accessory factors” that were not carbohydrates, proteins or fats. He showed that these accessory factors were required for growth in rats. These accessory factors were later in 1918 named “fat soluble” and in 1920 as “vitamin A”. Frederick was awarded the Nobel Prize for this discovery in 1929. The chemical structure of vitamin A was given by Paul Karrer, a Swiss chemist in 1931.

Sources of Vitamin A

There are a number of animal products that contain vitamin A such as meat, fish, liver (beef, pork, fish), butter, egg and milk. Beta carotene is found in fruits like pink grapefruit, apricots, mango, apricot, cantaloupe melon, papaya and vegetables like pumpkin, pea, tomatoes, sweet potatoes and carrots. Leafy vegetables, spinach, broccoli are also important sources of Vitamin A. The more the pigment present the more is the content of beta carotene in the vegetable or fruit. The plant products are more preferable as they are cholesterol and fat free unlike the many animal products fortified with vitamin A.

Deficiency or Excess both can be harmful

The deficiency -

• The deficiency of vitamin A in the body can lead to poor eyesight. A person who does not has sufficient intake of Vitamin A in his diet can suffer from Night blindness. The deficiency of vitamin A causes blindness in children. The deficiency is prevalent in the developing countries mostly. Southeast Asia and Africa are among the worst affected.
• The deficiency of vitamin can be divided into two stages or types. The first is the primary vitamin A deficiency and the second is the secondary vitamin A deficiency. The primary vitamin A deficiency occurs in people who do not have enough vitamin A in their diet. The secondary vitamin A deficiency occurs due to chronic mal-absorption of lipids, abnormal bile production and exposure to oxidants such as smoke and alcohol. Zinc deficiency is also found to trigger vitamin A deficiency as Zinc is required for proper transport, absorption and metabolism of vitamin A. Deficiency of vitamin A for a long time increases the risk of xeropthalmia which is complete blindness. There is an increase in the risk of infections in the urinary tract and ear as a result of decreased immunity in the body. Hyperkeratosis (a hair problem) and enamel hypoplasia are other problems that arise due to vitamin A deficiency.

The excess

• However the excess of anything is said to be harmful and in case of the consumption of Vitamin A the same rule is applicable. Too much of intake of Vitamin A by pregnant woman can cause birth defects in the child.
• A person who consumes more than 25,000 IU of vitamin A in a day is likely to suffer from acute vitamin A poisoning. However the limit is smaller for children.
• Excess consumption of vitamin A can lead to toxicity resulting in anorexia, vomiting, nausea, headache, and hair loss, pain in the abdomen, weak muscles and dizziness. In case of persistent excess intake a person can develop fever, weight loss, hair loss, fatigue, anemia, diarrhea and sleep deprivation that is insomnia. 
• Osteoporosis and hip fractures may also occur as the excess intake of vitamin A deters bone development.
• Excess vitamin A intake by a pregnant woman is found to affect the fetus.
• The carotenoid forms of vitamin A are less harmful. However excessive consumption of beta carotene may lead to carotenodermia. It is a condition in which the skin develops a yellow or orange color. Once the intake is brought down to the normal level the discoloration disappears.

The risk of toxicity due to high consumption of vitamin A doubles for smokers and chronic alcohol consumers. These people are exposed to greater risk of cancer of the lung, gastro intestine, esophagus and colon.

How to supplement Vitamin A to your body

It is best to include good variety of fruits, vegetables, legumes, lentils, whole grains and fortified dairy products in your diet. According to the Food and Nutrition Board of the Institute of Medicine the intake should be as follows-

Average intake for infants –

• 0-6 months – 400 micrograms per day
• 7-12 months – 500 micrograms per day

The recommended Dietary Allowance for vitamins in case of children under various age groups is as –

• 1-3 years – 300 micrograms per day
• 4-8years – 400 micrograms per day
• 9-13 years – 600 micrograms per day

For the young and adults –

• 14 years or older Males – 900 micrograms per day
• 14 years or older Females – 700 micrograms per day •
• During pregnancy the average recommended intake is higher -770 micrograms per day
• During the time of Lactation – 1200 micrograms per day

The values above give the average intake based on the age group and gender. One should consult one’s dietician or doctor for what intake best suits one’s body. Factors like pregnancy and health also affect the recommended intake.

Functions of Vitamin A

1. Vitamin A is an important vitamin essential for many functions of the body. It is essential to maintain a good intake of Vitamin A to have healthy skin, teeth, skeletal tissue, mucus membranes and soft tissues in the body.
2. It helps develop and maintain good vision. It is useful for low light and color vision.
3. Also important for reproduction and breast feeding functions in a woman.
4. It helps in the growth and development of the human body. Vitamin A is necessary for a good immune system.
5. The animal products contain vitamin A in ester form. These consist of retinyl palmitate that gets converted to retinol in the small intestine. As retinol it acts as the storage if vitamin and can be converted into retinal (the aldehyde).
6. The acid form that is retinoic acid is found to be helpful in cellular growth and differentiation.
7. The other metabolic functions of vitamin A include Gene transcription, embryonic development, reproduction, Haematopoiesis, bone metabolism and anti oxidant activity.

Uses of vitamin A in the medical field

The uses of vitamin A and its derivatives are –

• Retinyl palmitate a derivative of Vitamin A is used in skin creams.
• Retinoids are used in various medicines for the regulation of gene functions.
• Various derivatives of retinoic acid are used for curing dermatological problems.

My Conclusions

Vitamin A should be an important ingredient of our diet. A balanced intake of vitamin A will help you maintain good vision, healthy skin and hair besides regulating many other metabolic functions like gene transcription. The deficiency of the vitamin can result in poor vision, unhealthy hair and skin. However there is an upper limit of dosage for every age group that must be noted and the intake must not be in excess. The upper limit of intake of vitamin A varies according to age, gender and health. These average recommended values of intake may differ from person to person. The Excess intake of the vitamin can lead to toxicity and cause many health problems. The ill-effects will stop once the excessive intake is discontinued. So you must supplement your body with balanced dosages of vitamin A that can be found in many animal and plant sources like cod liver oil, meat, fish, carrots, spinach, green leafy vegetables and broccoli. And if you are not sure how to keep your diet balanced with adequate supplements of vitamin A then consult your doctor for the advice.