What are the major roles of vitamin A?

January 13, 2026 •

4 min read

According to the World Health Organization, vitamin A deficiency is the leading cause of preventable blindness in children globally. This fat-soluble nutrient, also known as retinol, plays several major roles throughout the body, supporting vital functions from cell growth to immune response.

Quick Summary

This article details the major roles of vitamin A, explaining its critical functions in vision, immune system regulation, cell growth and differentiation, and reproductive health. It also explores the different forms of the vitamin and its dietary sources.

Key Points

Vision is a primary function: Vitamin A is an integral part of the retina, enabling vision in low light and protecting the cornea from damage.
Immunity relies on vitamin A: This vitamin supports the growth of T and B cells and maintains mucosal barriers, which are critical for fighting infections.
Supports cell growth and differentiation: Through its active metabolite, retinoic acid, vitamin A regulates gene expression vital for the growth and development of cells and organs.
Crucial for reproduction: Essential for both male and female fertility and critical for proper fetal development during pregnancy, with careful intake necessary to avoid defects.
Dietary intake comes in two forms: Preformed vitamin A from animal sources and provitamin A carotenoids from plant foods, with different absorption rates and toxicity risks.
Prevents blindness globally: A deficiency in vitamin A is a leading cause of preventable blindness in children worldwide, underscoring its importance in public health.
Risk of toxicity: Since vitamin A is fat-soluble and stored in the body, overconsumption of preformed vitamin A, especially from supplements, can be harmful.
Maintains healthy skin: Vitamin A helps regulate skin cell function and development, with deficiency manifesting as dry, scaly skin.

The Foundational Role in Vision and Eye Health

Vitamin A is crucial for healthy vision because its active form, retinal, is a component of rhodopsin in the retina, which is necessary for perceiving light, especially in dim conditions. Deficiency can cause night blindness. It also maintains the cornea and conjunctiva, and severe deficiency can lead to xerophthalmia and permanent blindness.

Strengthening the Immune System

Known for its anti-inflammatory properties, vitamin A enhances the body's defense against infection. It aids in the development of T and B cells and maintains the integrity of epithelial and mucosal tissues, which act as barriers against pathogens. Deficiency increases susceptibility to infections, which is why vitamin A supplementation is used to reduce childhood mortality from diseases like measles.

Vitamin A's Impact on Cellular Function

Vitamin A metabolites, such as retinoic acid, influence gene expression, which is vital for cell growth, communication, and differentiation in various organs, including the heart and lungs. It also helps maintain healthy skin and tissues, with deficiency potentially causing dry, scaly skin.

Promoting Reproductive Health and Fetal Development

Essential for healthy reproduction in both men and women, vitamin A supports the male genital tract and sperm production. In women, it is involved in egg development and is critical for fetal growth, including the formation of vital organs. However, excessive preformed vitamin A during pregnancy can cause birth defects.

Comparison of Vitamin A Sources


Feature	Preformed Vitamin A (Retinol)	Provitamin A Carotenoids
Source	Animal products (liver, fish, eggs, dairy)	Plant foods (carrots, sweet potatoes, spinach, cantaloupe)
Active Form	Ready-to-use by the body	Converted to retinol by the body
Absorption	More readily absorbed by the body	Inefficient conversion, affected by genetics
Risk of Toxicity	High levels can be toxic, stored in the liver	Safe in high amounts, as conversion is regulated
Antioxidant Effect	Not a primary antioxidant	Many act as antioxidants, protecting against free radicals

A Balanced Approach to Vitamin A Intake

As a fat-soluble vitamin stored in the liver, balanced intake of vitamin A is important. Both deficiency and excess can cause health problems. A healthy diet usually provides sufficient vitamin A in developed countries. However, deficiency is a major issue in malnourished populations, particularly for children and pregnant women. Consulting a healthcare professional about supplementation is advisable.

Conclusion

Vitamin A is a crucial nutrient with fundamental roles in human health, including vision, immune function, cell growth, and reproduction. It is obtained from both animal and plant sources, and maintaining a balanced intake is essential. Deficiency can lead to serious issues like blindness, while excessive intake of preformed vitamin A can be harmful. A varied diet, potentially supplemented under medical guidance, is key to optimal health.

Authoritative Sources

All About Vision - Eye Benefits of Vitamin A and Beta-Carotene

The Multifaceted Functions of Vitamin A

Essential for Vision: Vitamin A is necessary for forming rhodopsin in the retina, a pigment crucial for vision in dim light, and it maintains the health of the cornea and conjunctiva to prevent dry eye and blindness.
Boosts Immune Defense: It is vital for the proper function of the immune system by supporting the growth and distribution of immune cells like T and B lymphocytes and reinforcing mucosal barriers against infection.
Regulates Cell Growth: Vitamin A, particularly in the form of retinoic acid, controls gene expression that directs cell growth, differentiation, and communication, which is important for the normal development and maintenance of many organs.
Supports Reproductive Health: For both men and women, adequate vitamin A is essential for proper reproductive function, including spermatogenesis in males and fetal development during pregnancy.
Maintains Skin Integrity: It helps form and maintain healthy skin and epithelial tissues, and a deficiency can lead to skin problems such as dry, scaly skin.
Acts as an Antioxidant: Provitamin A carotenoids, found in plant sources, function as antioxidants that protect cells from damage caused by free radicals.

FAQs

Question: What are the main dietary sources of Vitamin A? Answer: The main dietary sources of Vitamin A come in two forms. Preformed vitamin A (retinol) is found in animal products such as liver, eggs, milk, and cheese. Provitamin A carotenoids are found in colorful fruits and vegetables like carrots, sweet potatoes, spinach, and cantaloupe.

Question: Can a person get too much vitamin A from their diet? Answer: Yes, it is possible to consume too much preformed vitamin A, especially from supplements or high intake of certain foods like liver. Because it is fat-soluble and stored in the body, it can build up to toxic levels. This is less likely with provitamin A carotenoids from plants, as the body regulates their conversion.

Question: What are the signs of a vitamin A deficiency? Answer: The most common early signs include vision problems like night blindness. As it progresses, symptoms can include dry skin, dry eyes (xerophthalmia), an increased risk of infections, infertility, and in severe cases, irreversible blindness.

Question: Is vitamin A important during pregnancy? Answer: Yes, vitamin A is crucial for proper fetal development, including the formation of the heart, eyes, and lungs. However, excessive preformed vitamin A can be teratogenic (cause birth defects), so intake must be carefully managed.

Question: How does vitamin A affect the immune system? Answer: Vitamin A is essential for the function of the immune system by regulating cell-mediated and humoral immune responses. It helps with the growth of T-cells and B-cells and maintains the barrier function of mucosal linings in the respiratory and gastrointestinal tracts, which prevents infections.

Question: Is beta-carotene the same as vitamin A? Answer: Beta-carotene is a provitamin A carotenoid, which means it is a precursor that the body can convert into the active form of vitamin A (retinol). However, the conversion is not always efficient, and not all carotenoids are converted to vitamin A.

Question: How does vitamin A support skin health? Answer: Vitamin A supports skin health by maintaining the integrity and function of epithelial cells. It helps regulate the growth and differentiation of skin cells, with a deficiency manifesting as dry, scaly skin.

Frequently Asked Questions

The main dietary sources of Vitamin A come in two forms. Preformed vitamin A (retinol) is found in animal products such as liver, eggs, milk, and cheese. Provitamin A carotenoids are found in colorful fruits and vegetables like carrots, sweet potatoes, spinach, and cantaloupe.

Yes, it is possible to consume too much preformed vitamin A, especially from supplements or high intake of certain foods like liver. Because it is fat-soluble and stored in the body, it can build up to toxic levels. This is less likely with provitamin A carotenoids from plants, as the body regulates their conversion.

The most common early signs include vision problems like night blindness. As it progresses, symptoms can include dry skin, dry eyes (xerophthalmia), an increased risk of infections, infertility, and in severe cases, irreversible blindness.

Yes, vitamin A is crucial for proper fetal development, including the formation of the heart, eyes, and lungs. However, excessive preformed vitamin A can be teratogenic (cause birth defects), so intake must be carefully managed.

Vitamin A is essential for the function of the immune system by regulating cell-mediated and humoral immune responses. It helps with the growth of T-cells and B-cells and maintains the barrier function of mucosal linings in the respiratory and gastrointestinal tracts, which prevents infections.

Beta-carotene is a provitamin A carotenoid, which means it is a precursor that the body can convert into the active form of vitamin A (retinol). However, the conversion is not always efficient, and not all carotenoids are converted to vitamin A.

Vitamin A supports skin health by maintaining the integrity and function of epithelial cells. It helps regulate the growth and differentiation of skin cells, with a deficiency manifesting as dry, scaly skin.