Custom Search

           

 

Nutritional Pathology Online

"Keep your eyes beautiful and healthy"

Importance of Vitamin A in our daily diet

Pathology of Vitamin A deficiency

 

                    New Posts      Previous Posts

 

 

    


            

                                                                                                                        

Cartoon: Dr Sampurna Roy MD

 


As a toddler I enjoyed eating carrots and green leafy vegetables like spinach which surprised everyone.

Years later when I became a doctor I realized that my mother was not only an expert nutritionist, she also understood child psychology.

She prepared mouth watering vegetarian delicacies and awesome sweet dishes with sliced carrots in a way that I could never turn up my nose and throw tantrums. 

Carrots and other green vegetables are rich in Vitamin A and there is no toxic effect on children, unlike cod-liver oil which can cause toxicity if taken in large quantities.

In this post I will highlight few important facts about Vitamin A.

Vitamin A is one of the fat-soluble vitamins which is important to the health of skin, teeth and bones.

In herbivorous animals the carotenoid pigments, such as the carotenes of plants and vegetables, are converted into vitamin A in the intestine, absorbed, and subsequently stored in the liver.

Human beings acquire their supply either directly from the carotenoids in vegetable matter (Example: Carrots, beetroot, and green vegetables in general) or indirectly from animal or dairy products (Example:Preformed Vitamin A are highest in liver and fish oils. Milk and eggs also contain preformed vitamin A).

The concurrent absorption of fat and the presence of bile salts in the intestine favour vitamin A absorption.

Vitamin A deficiency is usually due to a deficient diet which is a common problem in the developing world.

Vitamin A deficiency may also occur as a complication of the malabsorption syndrome.

The blood level of carotene or vitamin A is used as a measure of the severity of the malabsorption.   

Effects of Vitamin A deficiency:

In vitamin A deficiency the most important effect is on the eye.

Eye:   

Vitamin A forms an essential component of rhodopsin, a pigment in the rods of the retina.

By absorbing light, rhodopsin initiates an electrical impulse that is transmitted to the brain and is interpreted as light.

The first sign of vitamin A deficiency, therefore, is night blindness.

It is known that vitamin A regulates the structure of certain epithelial cells.

The conjunctival epithelium loses its mucus-secreting goblet cells and becomes keratinized, thereby taking on the characteristics of epidermis.

An early sign is the formation of desquamating hyperkeratotic plaques on the conjunctiva at the lateral margin of the cornea.

These are triangular in shape, and appear as areas of dry foam. They are known as Bitot’s spots.

The lacrimal ducts show hyperkeratosis, so that the eye becomes dry and subject to cracking and infection.

The condition is called Xerophthalmia. 

In due course the cornea becomes cloudy, with infection it can soften (keratomalacia), so that the globe may become perforated.

The lens is then extruded, and blindness results.

Indeed vitamin-A deficiency is a leading cause of blindness in the world.

Ocular Lesions due to Vitamin A Deficiency:

1) Night blindness

2) Bitot’s spots

3) Xerophthalmia

4) Keratomalacia

5) Blindness

Skin:  

 

The skin shows dryness and follicular plugging.  Stratified squamous epithelium keratinizes and the keratin debris blocks the sweat glands and lacrimal glands.

Follicular hyperkeratosis is a skin disorder that results from occluded sebaceous glands.

This feature is often noted in patients with vitamin A deficiency.

Whether these changes are specific for vitamin A deficiency is not clear.

Other effects: The replacement of respiratory-type epithelium (with its goblet cells and cilia) by keratinized squamous epithelium is a factor in the production of respiratory infections.

The nasal passages, trachea and bronchi shows a transformation of the lining cells into a stratified epithelium which undergo extensive keratinization.

Vitamin A deficiency has been noted in patients with tuberculosis. Low serum retinol levels return to normal after antituberculosis treatment.

The deficiency of vitamin A in patients with tuberculosis may have contributed to the development of tuberculosis.

In the presence of a normal amount of vitamin A there is no evidence that an excessive intake can prevent respiratory infections.

In vitamin A deficiency the epithelial lining of the genitourinary tract (renal pelvis) tend to undergo squamous metaplasia.

Epithelial changes in the renal pelvis are occasionally associated with kidney stones.

                              

Kidney Stones                          Uterus                                Pancreas with duct

The lining epithelium of the pancreatic ducts, uterus, and salivary glands are also commonly affected.

In spite of the changes seen in the epithelium in vitamin-A deficiency, the biochemical nature of the defect is unknown.

If a small piece of skin is grown in organ culture and subjected to vitamin-A deficiency, it soon shows hyperkeratosis.

If an excess quantity of vitamin A is now added to the medium, the epithelium changes to a goblet-cell, mucous-secreting type.

There is no evidence, however, that excess vitamin-A in the human can convert normal keratinized epidermis into mucus secreting epithelium.

Toxicity of vitamin A.

Very large doses of vitamin A are toxic and can cause an increase in intracranial pressure with headache, blurring of vision,vomiting, and drowsiness.

This effect has been described by Arctic explorers when they ate polar bear liver, which is a very rich source of vitamin A.

Chronic poisoning can cause loss of hair, bone pains, calcification of ligaments and tendons, hyperpigmentation of the skin, liver damage, and psychiatric symptoms.

 

Visit: As a doctor today I prescribe Thiamine  (Vitamin B1) rich foods :Prevent Beriberi,Wernicke’s Encephalopathy, and Korsakoff’s Psychosis.

Visit: As a doctor today I prescribe  Riboflavin  (Vitamin B2) rich foods to prevent mucocutaneous and ocular lesions

Visit: As a doctor today I prescribe Niacin (Vitamin B3) rich foods to eradicate Pellagra - Prevent the 4 Ds - Dermatitis ; Diarrhea ; Dementia and Death

Visit: Eat Citrus Fruits everyday and keep Scurvy away- Pathology of Vitamin C Deficiency

Visit: As a doctor today I prescribe Vitamin K to prevent hemorrhage -The most important health problem of Vitamin K deficiency is Hemorrhagic Disease of the Newborn

Visit: As a doctor today I prescribe nutritious food for every hungry child  

 

Further reading:

Heterologous and sex differential effects of administering vitamin A supplementation with vaccines: a literature review.

Vitamin a deficiency and alterations in the extracellular matrix.

Vitamin A deficiency and xerophthalmic fundus in autoimmune hepatitis and cirrhosis.

Vitamin A and dendritic cell differentiation.

Role of vitamin A supplementation in the treatment of tuberculosis.

Range of ocular deformities in calves due to hypovitaminosis A.

Prevalence of vitamin A deficiency in South Asia: causes, outcomes, and possible remedies.

The influence of vitamin A supplementation on iron status.

 

                    New Posts      Previous Posts

Dr  Sampurna Roy  MD

Consultant Histopathologist (Kolkata - India)

 

 

Histopathology-India.net

 

Pathopedia-India.com

 

Surgical Pathology.com

 

Pathology-India.com

 

Dermpath-India

 

Infectious Disease Online

 

Pathology Quiz Online 

 

Paediatric Pathology Online

 

Pancreatic Pathology Online

 

Paraganglioma-Online

 

Endocrine Pathology Online

 

Eye Pathology Online

 

Ear Pathology Online

 

Cardiac Path Online

 

Pulmonary Pathology Online

 

Lung Tumour Online

 

Mesothelioma-Online

 

Nutritional Pathology Online

 

Environmental Pathology Online

 

Soft Tissue Tumour Online

 

GI Path Online-India

 

Gallbladder Pathology Online

 

E-book - History of Medicine  

 

Microscope - Seeing the Unseen

 

 

 

Disclaimer

Privacy Policy  

Advertising Policy

Copyright © 2017  pathopedia-india.com