Which Disease Happens Due to Lack of Vitamin A? A Comprehensive Guide

According to the World Health Organization, vitamin A deficiency is the leading preventable cause of childhood blindness globally. The primary disease that happens due to lack of vitamin A is xerophthalmia, a progressive eye condition that starts with night blindness and can lead to irreversible blindness if left untreated.

Quick Summary

An inadequate intake of vitamin A can cause xerophthalmia, a spectrum of eye conditions beginning with night blindness and progressing to severe corneal damage and irreversible blindness.

Key Points

• Night Blindness: One of the earliest and most common signs of vitamin A deficiency is night blindness, where individuals have difficulty seeing in dim light.

• Xerophthalmia: This is the clinical term for the full spectrum of eye diseases caused by severe vitamin A deficiency, ranging from dryness and foamy spots to permanent blindness.

• Immune System Impairment: A lack of vitamin A significantly weakens the immune system, increasing susceptibility to severe and sometimes fatal infections, particularly respiratory and diarrheal diseases.

• Non-Ocular Complications: Beyond eye problems, a deficiency can also cause skin issues like dryness and scaling (phrynoderma), and in children, can lead to impaired growth and development.

• Causes of Deficiency: The primary cause is inadequate dietary intake, but malabsorption disorders (like cystic fibrosis or Crohn's disease) and other infections can also lead to it.

• Prevention and Treatment: The deficiency is largely preventable with a balanced diet rich in vitamin A sources and treatable with supplements, although some damage, like corneal scarring, can be irreversible.

• Vulnerable Populations: Young children and pregnant women, especially in impoverished regions, are at the highest risk for developing a vitamin A deficiency.

Understanding the Role of Vitamin A

Vitamin A is a fat-soluble vitamin that is crucial for numerous bodily functions, including vision, immune system health, reproduction, and cell growth. Our bodies cannot produce it, so we must obtain it through our diet, either as preformed vitamin A (retinol) from animal products or as provitamin A carotenoids from plant sources. A sustained lack of this essential nutrient can lead to a range of health issues, with the most devastating consequences affecting the eyes.

The Spectrum of Disease: Xerophthalmia

The most well-known disease that happens due to lack of vitamin A is xerophthalmia, a clinical term for the full spectrum of eye manifestations caused by a severe deficiency. It is not a single condition but a progression of several stages of eye damage. The World Health Organization classifies the stages of xerophthalmia, which often begin mildly and worsen over time if the deficiency is not addressed.

Stages of Xerophthalmia

• Night Blindness (Nyctalopia): This is often the first and most common symptom. It is characterized by difficulty seeing in dim light or adjusting to changes from bright to dark environments. This happens because vitamin A is a key component of rhodopsin, the light-sensitive pigment in the rod cells of the retina. Without enough vitamin A, rhodopsin production is impaired, hindering low-light vision.
• Conjunctival Xerosis: At this stage, the conjunctiva—the thin membrane covering the white of the eye—becomes abnormally dry and non-shiny. The lack of moisture is caused by a decline in the function of mucus-secreting cells.
• Bitot's Spots: These are characteristic white, foamy, or triangular spots that appear on the whites of the eyes. They are a buildup of keratinized cells and are a clinical sign of vitamin A deficiency.
• Corneal Xerosis: As the deficiency progresses, the cornea becomes dry and hazy, and the patient may experience a lack of tear production. At this stage, prompt treatment can still save the patient's vision.
• Corneal Ulceration and Keratomalacia: This is the most severe and potentially blinding stage. The cornea softens and melts (keratomalacia), leading to ulceration. This can result in irreversible damage and permanent blindness.

Beyond the Eyes: Other Consequences

While the effects on vision are most prominent, a lack of vitamin A has other serious systemic health consequences that impact the entire body.

• Weakened Immune System: Vitamin A plays a critical role in maintaining the function and integrity of the skin and mucous membranes, which act as the body's first line of defense against infection. A deficiency compromises these barriers and impairs the immune response, making individuals, particularly children, more susceptible to severe and fatal infections, including respiratory and diarrheal diseases.
• Impaired Growth and Development: For children, vitamin A is essential for proper growth and development. A deficiency can lead to stunted growth and slow bone development.
• Reproductive Issues: A lack of vitamin A can also impact reproductive health and is associated with poor outcomes during pregnancy and lactation, as well as fertility problems.
• Skin Problems: The skin can also be affected, becoming dry, scaly, and itchy due to the impact on epithelial cell health. A specific skin condition called phrynoderma, or 'toad skin,' can also occur.

Causes of Vitamin A Deficiency

Vitamin A deficiency is rare in developed countries but remains a significant public health issue in many low-income nations, especially in Africa and Southeast Asia.

Primary and Secondary Causes of Deficiency

Cause	Description
Inadequate Dietary Intake	The most common cause in resource-poor regions, where diets often rely on vitamin A-poor staple foods like rice, millet, or cassava.
Malabsorption Disorders	In developed countries, chronic health conditions like cystic fibrosis, celiac disease, chronic pancreatitis, and liver disorders can interfere with the body's ability to absorb fat-soluble vitamins, including vitamin A.
Underlying Infections	Repeated gastrointestinal infections and diseases like measles can deplete the body's vitamin A reserves, with measles, in particular, shown to cause significant drops in serum retinol levels.
Bariatric Surgery	Some types of weight-loss surgery can alter the intestinal tract, leading to malabsorption of fat-soluble vitamins.

Who is at Highest Risk?

The most vulnerable groups include:

• Young children, especially those aged 6 months to 5 years.
• Pregnant and breastfeeding women.
• Individuals in regions with widespread malnutrition and limited access to varied diets.
• People with chronic malabsorptive diseases or liver disorders.

Preventing and Treating Deficiency

Prevention and treatment involve ensuring an adequate intake of vitamin A, either through diet or supplementation.

Key Strategies for Prevention

• Eat a varied diet: Include a range of vitamin A-rich foods in your meals.
• Cook and prepare vegetables properly: Mashing and cooking vegetables can aid absorption, but overcooking should be avoided as it can destroy the vitamin content.
• Utilize fortified foods: Many cereals, dairy products, and oils are fortified with vitamin A, providing an accessible source.
• Supplementation programs: In at-risk populations, supplementation programs, such as those recommended by the WHO, are crucial for preventing deficiency.

Vitamin A Rich Food Sources

• Animal Sources (Retinol): Liver, eggs, milk, cheese, and fatty fish like salmon.
• Plant Sources (Provitamin A Carotenoids): Dark green leafy vegetables (spinach, kale, broccoli), orange and yellow vegetables (carrots, sweet potatoes, pumpkin, squash), and fruits (mangoes, cantaloupe, papayas).

Treatment for Established Deficiency

For an established deficiency, especially with clinical symptoms like xerophthalmia, high-dose vitamin A supplementation is administered under medical supervision to correct the deficiency. This can reverse early symptoms like night blindness and dryness, but corneal scarring and permanent blindness cannot be cured.

Conclusion

While a deficiency is uncommon in many parts of the world, the devastating eye disease xerophthalmia, caused by a lack of vitamin A, remains a global health concern. The progression from mild night blindness to irreversible blindness is a preventable tragedy, especially in vulnerable populations. Understanding that which disease happens due to lack of vitamin A and its broader effects on immune function and growth is the first step toward effective prevention and treatment. By promoting diverse, nutrient-rich diets and targeted supplementation programs, the severe consequences of this deficiency can be mitigated. For more detailed clinical guidelines, see the World Health Organization's nutrition publications.

Frequently Asked Questions

What is the very first sign of vitamin A deficiency?

The very first and most common sign of vitamin A deficiency is night blindness, which is difficulty seeing or adapting to vision in dim light.

Can vitamin A deficiency cause blindness?

Yes, if left untreated, severe vitamin A deficiency can lead to irreversible blindness through a progressive condition called keratomalacia, where the cornea softens and ulcerates.

What are Bitot's spots?

Bitot's spots are white, foamy, or triangular-shaped deposits that appear on the whites of the eyes (conjunctiva), and are a classic sign of vitamin A deficiency.

What happens to the immune system with a lack of vitamin A?

A lack of vitamin A impairs the immune system by weakening the body's defensive barriers and reducing its ability to fight infections, particularly respiratory and diarrheal illnesses.

Which types of food are rich in vitamin A?

Foods rich in vitamin A include liver, dairy products, eggs, fatty fish, as well as plant sources like carrots, sweet potatoes, dark leafy greens, and mangoes.

Can a vitamin A deficiency be cured?

Yes, early stages of vitamin A deficiency, such as night blindness, can be reversed with proper diet and vitamin A supplementation. However, blindness from corneal scarring is irreversible.

Is vitamin A deficiency common in developed countries?

Vitamin A deficiency is very rare in developed countries but can occur in individuals with specific health conditions that cause malabsorption, such as cystic fibrosis, liver disease, or following bariatric surgery.

What are provitamin A carotenoids?

Provitamin A carotenoids are plant pigments, like beta-carotene, that the body converts into vitamin A. They are found in many brightly colored fruits and vegetables.