Vitamin A is a fat-soluble vitamin crucial for maintaining vision, supporting immunity, promoting cell growth, and enhancing skin health. This guide explores the benefits of vitamin A, its best dietary sources, and the risks associated with both deficiency and excess intake, helping you understand how to achieve a safe and effective intake.
What Is Vitamin A? Forms & Functions
Vitamin A is a fat-soluble vitamin essential for various physiological functions in the body, including vision, immune function, and cellular growth and differentiation.
It comprises a group of chemically related compounds, primarily retinol, retinal (also known as retinaldehyde), and retinoic acid [1]. Furthermore, provitamin A carotenoids, such as beta-carotene, form an essential part of this vitamin group, as the body can convert them into active vitamin A.
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The two primary forms of vitamin A are:
- Preformed Vitamin A (Retinoids): This includes retinol and retinyl esters, found predominantly in animal products (e.g., liver, dairy).
- Provitamin A Carotenoids: These are plant pigments (like beta-carotene) that the body converts into retinol. They are abundant in colourful fruits and vegetables.
Vitamin A plays a vital biological role in our bodies. It assists in the formation of rhodopsin, a protein in our retina that is essential for low-light and colour vision. Retinoic acid, another derivative of vitamin A, regulates gene expression and plays a crucial role in cell differentiation and growth [2].
Food Sources of Vitamin A
Vitamin A can be obtained from various dietary sources:
- Oily fish
- Yoghurt
- Cheese
- Eggs
- Milk
- Liver and liver products
- Leafy green vegetables (kale, spinach and broccoli)
- Orange and yellow vegetables (carrots, sweet potatoes and pumpkin)
- Yellow fruits (mango, papaya and apricots)
- Tomatoes
Preformed Vitamin A Sources (Retinoids): Liver and liver products, oily fish, eggs, milk, and cheese.
Provitamin A Carotenoid Sources: Orange and yellow vegetables (carrots, sweet potatoes, pumpkin), leafy green vegetables (kale, spinach, broccoli), and yellow/orange fruits (mango, papaya, apricots).
Science-Backed Health Benefits of Vitamin A
Vitamin A’s roles are multifaceted, impacting key systems throughout the body. Here is an overview of its most significant benefits:
1. Essential for Vision
Vitamin A is crucial for maintaining good vision. It is a component of rhodopsin, a light-absorbing pigment in the retina that facilitates low-light vision [3]. Inadequate levels can lead to night blindness (nyctalopia) and, in severe cases, to corneal damage (xerophthalmia) [3].
2. Supports Immune Function
Often called the “anti-infection vitamin,” Vitamin A is instrumental in maintaining the integrity of mucosal barriers (skin, respiratory, and gastrointestinal tracts), which act as the first line of defence against pathogens [4]. It also plays a key role in the development and function of various white blood cells (lymphocytes) that regulate the immune response [4].
3. Promotes Skin Health and Cell Growth
Vitamin A plays a crucial role in cell differentiation, which is essential for the development and maintenance of tissues and organs. It helps regulate the growth and renewal of skin cells [5]. Retinoids, a class of compounds derived from vitamin A, are commonly used in dermatology to treat conditions like acne and psoriasis under the guidance of a physician [5].
4. May Exhibit Antioxidant Properties
Vitamin A, particularly its provitamin A carotenoid forms like beta-carotene, exhibits antioxidant properties that help protect cells from damage caused by harmful free radicals [6]. This protection may reduce oxidative stress and may lower the risk of chronic diseases. It’s important to note that the role of vitamin A as an antioxidant versus a pro-oxidant is complex and depends on the chemical environment [6].
5. Role in Reproductive Health and Foetal Development
Vitamin A plays a crucial role in reproductive health in both men and women. It supports sperm development (spermatogenesis) in males and is essential for egg quality and normal embryonic and foetal development during pregnancy [2].
6. Potential Anti-Cancer Effects
Some observational studies suggest that a diet rich in natural sources of provitamin A carotenoids may be associated with a reduced risk of certain cancers by protecting cells from damage [7]. However, evidence regarding high-dose vitamin A supplements for cancer prevention is mixed, and they are not generally recommended for this purpose [7].
Vitamin A Deficiency and Toxicity Risks
Your body requires vitamin A for numerous essential functions, but both too little and too much can lead to serious health issues.
Risks Associated with Deficiency
- Vision Problems: The earliest sign is night blindness. Prolonged severe deficiency can lead to irreversible damage to the cornea and blindness (xerophthalmia) [3].
- Weakened Immune System: Deficiency can impair the production and function of immune cells, leading to increased susceptibility to respiratory and gastrointestinal infections [4].
- Increased Child Mortality: Globally, vitamin A deficiency remains a leading preventable cause of death in children under five [4].
- Anaemia: Vitamin A deficiency can exacerbate iron deficiency anaemia by interfering with iron metabolism [8].
Risks Associated with Excess Intake (Toxicity)
- Acute Toxicity: Can occur from ingesting a single, very large dose. Symptoms include nausea, vomiting, dizziness, blurred vision, and headache.
- Chronic Toxicity (Hypervitaminosis A): Can occur from daily consumption of high doses (well above the Tolerable Upper Intake Level) over time. Symptoms can include dry, rough skin, hair loss, liver damage, bone and joint pain, and increased pressure in the skull [1].
- Birth Defects (Teratogenicity): Excessive consumption of preformed vitamin A during pregnancy is associated with an increased risk of severe congenital disabilities [1]. Pregnant individuals must strictly adhere to recommended intake limits and should not take high-dose vitamin A supplements unless prescribed by a physician.
Takeaway
Vitamin A is a critical micronutrient that supports essential functions like vision, immunity, skin health, and cell growth. Balance is paramount: both deficiency and excess intake can lead to serious problems. Focus on a balanced diet including colourful fruits, vegetables, eggs, dairy, and fish, and follow age-appropriate intake guidelines. Never start a high-dose supplement without first consulting your doctor or a registered nutritionist.
Expert Quote:
“Vitamin A is essential for healthy vision, immunity, and skin maintenance, but both deficiency and excess can cause serious issues, so balance is key. Patients should be cautious of over-the-counter high-dose supplements, as the risk of toxicity, especially liver damage and teratogenicity, is real.”
Dr Anubha Karol
Frequently Asked Questions (FAQs)
Which foods are high in vitamin A?
Top sources include beef liver, sweet potatoes, carrots, spinach, and dairy products. Provitamin A carotenoids are found in orange and yellow fruits and vegetables.
Is vitamin A good for hair growth?
Vitamin A supports cell growth and scalp health, which helps maintain normal hair growth. However, consuming too much preformed vitamin A can paradoxically cause hair loss and should be avoided [1].
Which fruit has more vitamin A?
Among commonly consumed fruits, mangoes are one of the highest sources of provitamin A carotenoids.
How much vitamin A is safe per day?
The Recommended Dietary Allowance (RDA) for adult men is 900 micrograms (µg) RAE (Retinol Activity Equivalents) per day and 700 µg RAE per day for adult women [1].
What is a toxic level of vitamin A?
The Tolerable Upper Intake Level (UL) for preformed vitamin A for adults is 3,000µ g RAE (10,000 IU) per day [1]. A daily intake consistently above this level increases the risk of chronic toxicity, leading to symptoms such as dizziness, nausea, and liver damage.
References
[1] National Institutes of Health (NIH) Office of Dietary Supplements. (2023). Vitamin A and Carotenoids: Fact Sheet for Health Professionals. Retrieved October 28, 2025, from https://ods.od.nih.gov/factsheets/VitaminA-Health/
[2] Clagett-Dame, M., & Knutson, D. (2011). Vitamin A in reproduction and development. Nutrients, 3(4), 385–428. https://doi.org/10.3390/nu3040385
[3] Gilbert, C. (2013). The eye signs of vitamin A deficiency. Community Eye Health, 26(84), 66–67. https://pmc.ncbi.nlm.nih.gov/articles/PMC3936686/
[4] Huang, Z., Liu, Y., Qi, G., Brand, D., & Zheng, S. G. (2018). Role of vitamin A in the immune system. Journal of Clinical Medicine, 7(9), 258. https://doi.org/10.3390/jcm7090258
[5] Fisher, G. J., Datta, S. C., & Voorhees, J. J. (2009). The scientific basis for retinoid use in the treatment of photodamage. Seminars in Dermatology, 18(4), 263-272. https://doi.org/10.1016/S0738-081X(99)80058-2
[6] Dao, D. Q., Ngo, T. C., Thong, N. M., & Nam, P. C. (2017). Is vitamin A an antioxidant or a pro-oxidant? The Journal of Physical Chemistry B, 121(40), 9348–9357. https://doi.org/10.1021/acs.jpcb.7b07065
[7] Goodman, G. E., Lee, S. K., Tangen, C. M., et al. (2004). The association between serum retinol, beta-carotene, alpha-tocopherol, selenium, and lung cancer risk in the Beta-Carotene and Retinol Efficacy Trial. Cancer Epidemiology, Biomarkers & Prevention, 13(7), 1144–1150. https://doi.org/10.1158/1055-9965.EPI-03-0300
[8] Semba, R. D. (1999). Vitamin A and iron interactions in childhood infection and anaemia. Nutrition Research Reviews, 12(1), 1-15. https://doi.org/10.1079/095442299108728952
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