What are the main harms caused by vitamin A deficiency?

October 26, 2025 •

4 min read

Globally, vitamin A deficiency is the leading cause of preventable childhood blindness, affecting an estimated 250,000 to 500,000 children each year, half of whom die within 12 months of losing their sight. A lack of this vital micronutrient has devastating and widespread harms beyond just vision loss, impacting immune function, growth, and overall survival.

Quick Summary

Inadequate vitamin A intake can lead to a spectrum of severe health issues, from vision impairment and irreversible blindness to a profoundly weakened immune system and increased risk of infectious diseases. It also causes stunted growth in children and can affect reproductive health.

Key Points

Irreversible Blindness: Severe vitamin A deficiency can progress from night blindness to permanent eye damage, including corneal ulcers and keratomalacia, leading to irreversible blindness.
Weakened Immune System: The deficiency profoundly impairs immune function, making the body highly vulnerable to infections, particularly respiratory and diarrheal diseases.
Increased Mortality Rate: In children, a compromised immune system due to vitamin A deficiency leads to a significantly higher risk of illness and death from common infections like measles.
Stunted Growth: Lack of sufficient vitamin A can cause delayed growth and slowed bone development in children, impacting their overall health and development.
Dermatological Issues: The deficiency impairs the health of epithelial tissues, leading to skin problems such as dryness, scaling, and hyperkeratosis.

Understanding Vitamin A's Crucial Role

Vitamin A is a fat-soluble vitamin essential for a multitude of physiological processes, including vision, immune function, cellular differentiation, and growth. The body cannot produce vitamin A on its own, so it must be obtained from dietary sources, including preformed vitamin A (retinoids) from animal products and provitamin A carotenoids from plant sources. A chronic and severe insufficiency of this key nutrient, particularly in vulnerable populations like young children and pregnant women in developing countries, leads to profound and often irreversible health harms.

Ocular Complications: A Pathway to Blindness

One of the most well-known consequences of vitamin A deficiency is its progressive damage to the eyes, a condition known as xerophthalmia. The ocular symptoms typically progress through several stages, starting with relatively mild issues and escalating to permanent blindness if left untreated.

Night Blindness (Nyctalopia)

The earliest and most common clinical sign is night blindness, or nyctalopia. It affects the ability to see in low-light conditions because vitamin A is a crucial component of rhodopsin, the light-sensitive pigment in the retina's rod cells. Without enough vitamin A, the regeneration of this pigment is impaired, making it difficult or impossible to adapt to darkness. Night blindness is reversible with prompt vitamin A supplementation.

Xerophthalmia (Dry Eye)

As the deficiency worsens, the whites of the eyes (conjunctiva) become dry and wrinkled, losing their normal luster. This happens because a lack of vitamin A causes a loss of mucus-secreting goblet cells, impairing the production of tears. This dry, gritty sensation is a precursor to more severe damage.

Bitot's Spots

Often accompanying conjunctival xerosis are Bitot's spots, which are distinctive, foamy, white or grayish patches that appear on the conjunctiva. They are formed by a buildup of keratinized cells and gas-forming bacteria. These spots are considered a key clinical indicator of vitamin A deficiency.

Corneal Damage and Irreversible Blindness

The most severe and dangerous stage of deficiency-related eye damage involves the cornea, the transparent outer layer of the eye. This includes:

Corneal Xerosis: A progressive drying and haziness of the cornea.
Corneal Ulceration: The damaged corneal epithelium breaks down, leading to open sores and risking infection.
Keratomalacia: A severe, acute, and potentially rapid-onset condition where the cornea undergoes liquefactive necrosis, causing it to soften and melt. This can occur over a matter of days and almost always leads to irreversible blindness and a high risk of death, especially in young children.

Compromised Immune System Function

Vitamin A is vital for the proper functioning of the immune system, including both innate and adaptive immunity. A deficiency significantly weakens the body's ability to fight off infections, turning common illnesses into life-threatening conditions. This is particularly dangerous for children.

Mucosal Barrier Breakdown: Vitamin A maintains the integrity of epithelial and mucosal tissues in the respiratory, gastrointestinal, and urinary tracts. Deficiency leads to a breakdown of these protective barriers, making it easier for pathogens to enter the body.
Impaired Immune Response: It diminishes the function of key immune cells like neutrophils, macrophages, and natural killer (NK) cells. It also impairs antibody-mediated responses, further compromising the body's defenses.
Increased Risk of Infections: This suppressed immunity results in an increased susceptibility to a range of infections, most notably respiratory and diarrheal infections. In areas where vitamin A deficiency is widespread, it is linked to higher fatality rates from diseases like measles.

Growth and Development Issues

For growing children, an adequate intake of vitamin A is critical. A deficiency can have severe impacts on their development.

Delayed Growth: Children with vitamin A deficiency often experience delayed growth and development. Even mild, subclinical deficiency can affect growth rates and slow bone development.
Increased Mortality: Children who are deficient are at a significantly higher risk of mortality. Studies have shown a strong link between vitamin A deficiency and increased deaths from common childhood infections.

Comparison of Healthy vs. Deficient Vitamin A States


Health Aspect	Sufficient Vitamin A	Vitamin A Deficient State
Eyes	Normal vision, especially in low light; moist, lubricated cornea; proper retinal function.	Night blindness; dry eyes (xerophthalmia); Bitot's spots; corneal ulcers; permanent scarring or blindness.
Immune System	Robust immune response; effective defense against infections; healthy mucosal barriers.	Weakened immunity; increased susceptibility to infections (respiratory, diarrheal); higher mortality rates from common illnesses.
Growth	Normal growth and development in children; healthy bone development.	Stunted growth; slower development; increased mortality risk in children.
Skin & Mucous Membranes	Healthy, smooth skin; intact mucosal linings of respiratory and GI tracts.	Dry, scaly, itchy skin (hyperkeratosis); breakdown of epithelial and mucosal barriers.
Reproduction	Supports healthy reproductive function in both males and females.	Potential for infertility and poor pregnancy outcomes in women.

Conclusion

The harms caused by vitamin A deficiency are extensive, impacting crucial bodily functions from sight and immunity to growth and development. While the most dramatic consequence is irreversible blindness, the compromised immune function poses an equally grave threat, significantly increasing the risk of life-threatening infections and mortality. Public health interventions focusing on improving dietary intake through fortification and supplementation, especially for high-risk populations, are essential to prevent these devastating and preventable health outcomes. Ensuring adequate vitamin A intake is a critical step toward protecting global health, particularly for infants and young children.

Frequently Asked Questions

Vitamin A deficiency is the leading cause of preventable blindness in children globally. An estimated 250,000 to 500,000 children become blind each year due to this deficiency.

Night blindness (nyctalopia) is an early symptom of vitamin A deficiency, making it difficult to see in low-light conditions. It is caused by an impaired production of visual pigments in the retina, which requires vitamin A to function properly.

Vitamin A is critical for immune function. A deficiency can damage the body's protective mucosal barriers and diminish the effectiveness of key immune cells, leading to a severely compromised immune response and increased susceptibility to infections.

Bitot's spots are a clinical sign of vitamin A deficiency, appearing as foamy, white or grayish triangular patches on the conjunctiva (the whites of the eyes). They are a buildup of keratinized epithelial cells.

Night blindness and some early eye symptoms are reversible with adequate vitamin A supplementation. However, vision loss due to corneal ulcers and scarring (keratomalacia) is permanent and cannot be reversed.

Other signs of vitamin A deficiency include dry and scaly skin (hyperkeratosis), poor wound healing, frequent infections, stunted growth in children, and reproductive issues.

Infants, young children, and pregnant and breastfeeding women are at the highest risk, especially in low-income regions of Africa and Southeast Asia where diets may lack sufficient vitamin A.