- What is the importance of Vitamin A in our bodies?
- Vitamin A is a fat soluble vitamin which naturally occurs in a lot of food items
- There are many forms of Vitamin A needed by the body. Like:
- Retinal: It is a substance which is required for rhodopsin formation and vision. Rhodopsin is a pigment found in rod cells of the retina and is extremely light sensitive.
- Retinol along with its derivatives are essential for maintenance of the skin and mucosal cells
- It also serves as a barrier against infection
- Retinol is also required for white blood cell (WBC) development
- Retinoic acid: It is the main hormonal metabolite and is used for growth and differentiation of epithelial cells
- Vitamin A is important for:
- The eye needs to create certain pigments for the photoreceptor cells in the retina to work properly
- Retina is a tissue which is located at the back of the eye. Light reflected from objects, enters the eyes and gets reflected in the tissues.
- When light strikes the retina, retinol is converted to retinal and given to the rod cells
- Rod cells help in vision in the dark. Inside it, the retinal binds to a protein called as opsin
- The opsin changes its shape and a nerve impulse is triggered
- The nerve impulse travels to the brain and provides it information about the objects inside its visual field
- Retinal is again converted to retinol, completing the visual cycle
- To view the entire spectrum of light, the pigments in the photoreceptor cells are very essential
- Vitamin A also nourishes the cornea, a clear film in front of the eye. Without it, there would not be enough lubrication for the eye.
- Regulation of Genes:
- The genes contain the code for vital proteins needed by the body. The proteins are required for the body to carry out its daily functions.
- When the proteins are needed, the genetic code is transcribed (synthesis of genetic code by copying from existing DNA)
- Genetic transcription is closely monitored. The retinoic acid in Vitamin A controls when genes are transcribed and how fast it is done.
- Support of the Immune System:
- The retinol in the Vitamin A is used for maintaining cells of the skin and the lining of the digestive, urinary and respiratory tracts
- These cells form a key part of the immune system
- The cells form the first line of defense against infection
- Vitamin A is also used to form white blood cells
- Red Blood Cell Production:
- Vitamin A helps in the production of Red Blood Cells (RBCs) by stem cells
- The iron component of hemoglobin in RBCs is assimilated by Vitamin A
- What are the risks of consuming too much Vitamin A?
Too much of Vitamin A is called as toxicity. It can cause:
- Birth Defects
- Abnormalities of the liver
- Disorders of the Central Nervous System
- Decrease of bone mineral density, leading to an increased risk of osteoporosis
- Excess of Vitamin A suppresses the building up of bones and increases its breakdown
- There is interference in the calcium absorption by Vitamin D due to excess of Vitamin A
Vitamin A toxicity can lead to:
- Blurry vision
- Muscular pain
- Bone and joint pain
- Weight loss
- Hair loss
- Liver dysfunction
- Inflammation of the tongue
- Even Death
- How much Vitamin A can you consume in a day?
The maximum amount of vitamin A that can be consumed is given below. This does not include the amount prescribed by a doctor for a medical condition.
|Stages of Life||Maximum limit (IU)|
|From Birth to 1 year||2000|
|1 to 3 years||2000|
|4 to 8 years||3000|
|9 to 13 years||5667|
|14 to 18 years||9333|
- Which foods are recommended to get Vitamin A in right proportion?
Vitamin A can be found naturally in many foods and also added to some, like milk and cereal. Eating variety of food can give the required dose of Vitamin A. Like:
- Leafy green vegetables
- Carrots, sweet potatoes and pumpkins and other orange vegetables containing a pigment called as beta carotene
- Fruits like mangoes, cantaloupes and apricots
- Some types of fish like salmon
- Dairy products
- Cod liver oil
- What are the types of Vitamin A deficiency?
Primary Vitamin A deficiency:
Secondary Vitamin A deficiency:
- Prolonged deficiency in the diet; especially in areas where rice is the staple food (no carotene in the diet)
- Protein- energy malnutrition (a form of malnutrition due to insufficient protein or calorie consumption) like marasmus or kwashiorkor, occurs along with Vitamin A deficiency. This is mainly due to deficiencies in the diet. Storage of Vitamin A as well as its transportation is also hindered.
- This type of deficiency arises when:
- There are difficulties in converting carotene to Vitamin A
- Absorption is reduced
- Less transportation of Vitamin A
- Storage of the vitamin decreases
- Gastro-intestinal defects leading to malabsorption of vitamins, can cause Secondary Vitamin A deficiency.
- Vitamin A is a fat soluble vitamin, so a low-fat diet can cause its abnormal absorption
- Zinc deficiency disrupts the vitamin's transportation and absorption
- Other factors due to which this deficiency is caused, are:
- Abnormal production of bile
- Exposure to Cigarette smoke
- Secondary Vitamin A deficiency occurs due to diseases like:
- Giardiasis: An infection in the small intestine.
- Coeliac disease: The immune system has an abnormal reaction to gluten (a type of protein) and causes small bowel damage.
- Tropical sprue: Malabsorption disease of the small intestine.
- Cystic Fibrosis: A hereditary disorder that affects the lungs and the digestive system.
- Cirrhosis: Liver damage which leads to scarring and liver failure.
- Duodenal bypass surgery: Blockage of the duodenum, relieved with an operation.
- Bile duct obstruction: Obstruction due to gallstones.
- What are the different factors that lead to Vitamin A deficiency?
- Malnutrition is the primary reason of Vitamin A deficiency
- People whose diet does not consist of animal-based food products are at a higher risk of deficiency
- Vegetables; especially those which are orange in colour (like carrots, squashes etc.), are a rich source of the vitamin. People who do not consume enough vegetables also suffer from this deficiency.
- Breast milk is a good source of Vitamin A for newly born infants. Women who do not breastfeed their children, put them at a higher risk.
- Pregnant or lactating women with insufficient Vitamin A are more likely to have children with low levels of the vitamin
- Certain ailments can cause incorrect absorption of the vitamin, which can lead to deficiency
- Over excretion of urine, can cause Vitamin A deficiency, due to diseases like:
- Urinary Tract Infections (UTI)
- Nephritis (Kidney inflammation)
- Hepatic diseases make the storage of Vitamin A in the body difficult, causing deficiency
- What are the visible symptoms of Vitamin A deficiency?
- Night blindness or reduced vision at night-time or in dim light
- Outlines of images cannot be distinguished due to low light
- Daytime vision may be good until the night-blindness takes a severe form
- Severe form of night-blindness
- Outer membrane called as the conjunctiva loses its goblet cells (cells responsible for secreting mucus to keep the eye lubricated)
- The loss of goblet cells lead to xerophthalmia, where the eyes cannot produce tears
- The damaged goblet cells collect around the outer eye, forming debris around it
- The debris can cause infection or even blindness
- For advanced deficiency, Keratomalacia may occur. During this condition, the cornea becomes misty and eroded and may even be destroyed.
- Formation of Bitot's spots:
Abnormal growth and keratinisation (conversion into keratin protein) of squamous cells of the conjunctiva, leading to irregular patches on the whites of the eye
- Eye Inflammation:
The inflammation can spread to the eyelids and the nearby tissues including the cornea
- The child or adult may be prone to respiratory or urinary infections
- Children may suffer from growth retardation
- Skin becomes dry and flaky
- What complications are associated with Vitamin A deficiency?
Secondary conditions, symptoms and other diseases caused by Vitamin A deficiency are the complications related to the deficiency.
Diseases associated with the complications are:
Presence of poikilocytes or abnormally shaped blood cells, in the blood stream
- Night Blindness (refer to question No. 7)
A medical condition where patient's blood cells are of different sizes
- Bitot's Spots:
Keratin buildup in the conjunctiva forming oval, triangular or irregular shapes
Vision is impaired as the cornea becomes soft and increasingly cloudy
A condition where there is unusual dryness of the eyes as it fails to produce tears
Condition of the erythrocytes (Red Blood Cells) where they are found to be abnormally small, with respect to mean corpuscular volume.
- Dry Eyes
Inflammation of the cornea
- What are the different tests suggested for Vitamin A deficiency/excess?
- What are the normal values of tests recommended for Vitamin A deficiency/excess?
Vitamin A blood test:
Deficiency: Less than 50 mcg/dL
Excess: More than 200mcg/dL
Serum retinol levels:
Deficiency: Less than 28µg/dL
- What are the rates for performing tests for Vitamin A deficiency/toxicity?
There are a variety of factors that affect the cost of conducting diagnostic tests for Vitamin A deficiency or toxicity. It depends on the type of test, the city or even the hospital or diagnostic centre for the tests. To get a comprehensive list of the rates of doing tests in your city, click HERE.
- What are the different treatment methods for Vitamin A deficiency?
Early diagnosis of the deficiency is very essential before the state has worsened. Only then can it be treated:
- A diet rich in Vitamin A is usually the best treatment
- Carotene rich green-leafy and orange vegetables
- Fortified food (Adding vitamins to staple food) helps to prevent deficiency. Addition of the following elements leads to fortification :
Food items which are fortified are:
- Retinol acetates
- Retinyl palmitate
- Retinal ester
If deficiency is detected, then Vitamin A rich food should be eaten rather than fortified food.
- Cooking oil
- Milk/Milk powder
- Vitamin A can be taken orally in the form of supplements as well as in injectable form. People suffering from acute deficiency can be given:
- Intra-muscular (I.M) Vitamin A solution
- Aqueous Intra-Venous (I.V) supplement
- Treatment for the deficiency depends on its stage and is also different for various age groups. If family members are suffering from this deficiency, then it is imperative to get tested immediately.
- How can Vitamin A deficiency be prevented?
- Food rich in carotene is absorbed better when ingested with some fat. Diet should include:
- Dark green leafy vegetables
- Brightly coloured fruits (eg. papayas or oranges)
- Yellow vegetables (eg. Squash, pumpkin)
- Vitamin A fortified milk
- Egg yolks
- Fish liver oils
- Five servings of fruits and vegetables is mandatory for intake of beta-carotene
- Food items fortified with Vitamin A like bread, biscuits and energy bars can be included in the diet
- People at risk of this deficiency; especially children between the ages of 6 months to 5 years, should be given vitamin supplements to prevent mortality and blindness
- What is Keratomalacia?
It is an ocular (related to the eye) condition due to serious Vitamin A deficiency. The deficiency may be dietary or because of malabsorption of nutrients.
At first, Bitot's Spots may appear on the eye (refer Question No.7).
If it is still not treated, then the corneas might soften, leading to its infection and then rupture. The final stage is blindness.
In some developing countries Keratomalacia is the primary reason of childhood blindness.
In developed countries, such malnutrition is rare. It occurs as a secondary condition associated with defects in :
These defects are related to diseases such as:
- Transportation of Vitamin A
- Celiac disease
- Ulcerative colitis
- Cystic Fibrosis
- Liver diseases
- Intestinal bypass surgery
- What is the prognosis for Vitamin A deficiency?
Prognosis is good if the treatment is done in the early stages of the deficiency. In later stages it might be fatal. Some conditions like keratopathy (appearance of calcium on the cornea), keratomalacia (refer question No. 14) and rupture of the cornea, are irreversible.
- If there are mild problems in the eye, immediate treatment can lead to sight preservation without any permanent damage
- In developing countries, severe deficiency goes hand-in-hand with severe malnutrition. This often leads to death. Mortality is 50% for infants with this deficiency.
- 40% of patients with corneal xerophthalmia die after one year. 25% go totally blind and the rest of the patients remain partially blind.
- How can you get more Vitamin A?
- Vitamin A is a fat soluble vitamin. For ideal absorption of the vitamin into blood, carotenoids need to be ingested with some fat.
- Vitamin A rich food includes:
- Dark green-leafy vegetables
- Dried apricots
- Fruits like banana, jackfruit, mango and papaya
- What do you mean by Hypervitaminosis?
Hypervitaminosis A also called as Vitamin A toxicity, is a condition when there is too much Vitamin A in the body.
The condition can be acute or chronic:
- Acute: It usually occurs if there is too much of intake of the vitamin, in a short span of time.
- Chronic: If there is buildup of Vitamin A over a long period of time.