Discover the properties of vitamin A, where to find it in your diet, the symptoms of deficiency and excess, and how to effectively maintain your levels.
Table of Contents
- What is Vitamin A? Its Role in the Body
- Natural Sources of Vitamin A – What Should You Eat?
- Key Properties of Vitamin A
- Symptoms of Vitamin A Deficiency and Risk Factors
- Excess Vitamin A – Health Effects and Risks
- Supplementation and Prevention – How to Maintain an Appropriate Level of Vitamin A?
What is Vitamin A? Its Role in the Body
Vitamin A is a fat-soluble organic compound that plays a key role in the proper functioning of the human body. It is a group of chemicals encompassing retinoids and carotenoids, with retinol being the most biologically active form. The human body cannot synthesize vitamin A on its own, which is why it must be supplied through food. Vitamin A exists in two forms—preformed vitamin A (retinol and retinyl esters) from animal sources, and provitamin A (most commonly beta-carotene) from plant sources, which the body converts into its active form. Absorption of this vitamin occurs in the small intestine and it is mainly stored in the liver. Vitamin A is vital not only for vision and the correct functioning of the visual system, but also affects numerous biological and health functions, integral to daily life. In practice, vitamin A is involved in the signal transduction of light in the retina, where retinal (a form of vitamin A) present in rhodopsin (the light-sensitive protein) enables proper vision both in strong and low light. That’s why vitamin A deficiency manifests, among others, as night blindness. Apart from its key role in the visual system, vitamin A is important for maintaining the integrity and correct function of the skin and mucous membranes, protecting them from infections and dehydration by supporting epithelial regeneration and mucous production. This helps maintain a protective barrier, preventing the entry of pathogens and harmful environmental factors.
However, the role of vitamin A goes far beyond supporting the skin and vision. It actively participates in cell growth and differentiation, influencing development and tissue repair, especially during early life, pregnancy, and puberty. It is essential for proper immune system functioning—strengthening natural immunity by activating and stimulating white blood cells (T and B lymphocytes) to fight bacteria and viruses. Regularly supplying adequate vitamin A helps minimize the risk of infections and, when illness does occur, speeds up wound healing and regeneration of mucous membranes in the respiratory and digestive tracts. Vitamin A is also crucial for fertility—in both women and men it participates in the synthesis of sex hormones, proper development of reproductive cells, and the processes of embryogenesis. Additionally, its presence supports bone and dental health, proper skeletal mineralization, and protects cells from free radicals due to its antioxidant properties. Vitamin A also plays a significant role in iron metabolism—facilitating its absorption and aiding in hemoglobin synthesis, which helps prevent anemia. A deficiency can lead to a wide range of serious disorders—from impaired vision and skin changes to frequent infections and stunted growth in children. Vitamin A is so fundamentally important that it should be part of the daily diet at all ages to ensure optimal functioning of all the body’s systems and tissues.
Natural Sources of Vitamin A – What Should You Eat?
Vitamin A in nature appears as retinol and its derivatives (preformed vitamin A) as well as carotenoids, with beta-carotene being the most important and considered to be provitamin A. Retinol sources are mainly animal-based products, the richest examples being liver (beef, pork, poultry, fish), cod liver oil, butter, full-fat milk, aged cheeses, cream, and egg yolks. Liver, as an animal’s storehouse of vitamin A, provides the largest amounts—a small weekly portion covers an adult’s entire needs. Cod liver oil is also a traditional dietary supplement very high in retinol; however, in daily life, we more often consume milk, cheese, and eggs, which can systematically provide this essential nutrient. Notably, fat in dairy products aids vitamin A absorption since this vitamin is fat-soluble; skimmed alternatives are not as good a source. Eggs, especially yolks, can supplement vitamin A intake, but should be consumed in moderation due to cholesterol content. Among fish, cod and halibut liver are particularly high in retinol, but smaller amounts are present in fatty marine fish like mackerel or salmon.
Plant sources of vitamin A are vegetables and fruits rich in carotenoids, which the body can convert to its active form when needed. The best plant-based sources of beta-carotene are carrots, sweet potatoes, pumpkin, spinach, kale, Swiss chard, red and green bell peppers, sorrel, and lettuce. Fruits rich in beta-carotene include apricots, mango, cantaloupe melon, peaches, plums, as well as dried apricots and prunes. Dark green, orange, and yellow vegetables and fruits usually contain more carotenoids, and thus are the most valuable sources of provitamin A. Beta-carotene absorption from plant foods is increased if eaten with fat—even adding a teaspoon of olive oil or butter to a carrot or spinach salad can significantly improve utilization. Due to differences in bioavailability (retinol from animal products is absorbed much better than plant carotenoids), vegetarians or vegans should pay particular attention to regularly consuming high quantities of beta-carotene–rich fruits and vegetables, while properly composing their meals. Fortified foods, such as margarine enriched with vitamin A, can also serve as an additional dietary source, especially where traditional foods are limited. For optimal daily requirement coverage and healthy body function, diversify your diet with both plant and animal vitamin A sources.
Key Properties of Vitamin A
For decades, vitamin A was regarded mainly as a nutrient supporting proper vision; however, contemporary studies clearly show its biological activity affects many bodily systems. One of the most important functions of vitamin A is its involvement in the visual process, especially under low light conditions—it is part of rhodopsin, a pigment in the retina that enables vision in dim light. Thanks to an adequate vitamin A level, eyes can adapt to changing light intensities. A deficiency leads to so-called “night blindness,” or impaired vision at dusk, and may also promote dryness of the conjunctiva and cornea, possibly resulting in irreversible blindness in extreme cases. However, vitamin A’s role is not limited to eye health. It is essential for proper differentiation of epithelial cells and tissue regeneration. This ensures the tightness, elasticity, and healthy appearance of the skin and mucous membranes, protecting against external factors and microbial invasion. Vitamin A has strong antioxidant properties—it neutralizes free radicals that damage cells, accelerate tissue aging, and contribute to various civilization diseases, including cancer. Active forms of vitamin A also support wound healing by accelerating cell renewal and strengthening skin defense mechanisms. It is key to the body’s growth processes, ensuring proper development of cells, especially bone cells—hence, sufficient amounts are necessary for growing children, adolescents, and pregnant or breastfeeding women.
Vitamin A is also crucial for regulation of the immune response, enhancing both innate (physiological barriers of skin and mucous membranes) and acquired (lymphocyte response, antibody action) immunity. It helps the body fend off bacterial, viral, and parasite attacks. People who regularly consume enough vitamin A suffer fewer upper respiratory infections and seasonal illnesses, and recover faster from illness. Importantly, vitamin A is critical for fertility, affecting the production of reproductive cells in both sexes, supporting pregnancy, and contributing to the development of organs in embryos and fetuses, such as the heart, lungs, kidneys, and eyes. This vitamin also affects gene activity linked to the cell cycle and apoptosis (cell death), influencing the health and balance of the entire body. It supports bone mineralization, strengthens teeth, and aids iron absorption, thereby preventing anemia. Studies also show that vitamin A in the diet helps maintain proper cholesterol levels and may protect liver and kidney cells. Thanks to its diverse metabolic functions, vitamin A remains a cornerstone dietary nutrient for long-term health, physical and mental performance, and resistance to environmental stressors.
Symptoms of Vitamin A Deficiency and Risk Factors
Vitamin A deficiency is a serious form of malnutrition with numerous, multi-dimensional health effects. The most recognizable and characteristic symptom is night blindness (nyctalopia), or impaired vision at dusk and in low-light conditions, caused by impaired production of rhodopsin—a pigment in the retina essential for night vision. With worsening deficiency, further ocular changes can develop, including dryness of the conjunctiva and cornea (xerophthalmia), Bitot’s spots on the eyeballs, and in extreme cases, complete blindness. Dermatological symptoms include rough, dry, and flaky skin, especially on elbows, knees, or buttocks, and follicular keratosis (“goose skin”), resulting from disrupted epidermal renewal. Mucous membranes also lose elasticity, becoming dry and more susceptible to cracking and bacterial or viral infections—those lacking vitamin A have increased susceptibility to respiratory, digestive, and genitourinary infections. In children, deficiency can cause stunted growth, delayed physical development, impaired immunity, and even increased risk of death in cases of severe infection. In adults, it may cause brittle hair and nails, chronic fatigue, and reduced immune system efficacy. Vitamin A supports antibody production and tissue repair, so its absence results in slower wound healing, elevated inflammation, and difficult infection management. For pregnant women, prolonged deficiency can cause serious fetal developmental problems—increasing the risk of preterm birth, low birth weight, sensory organ abnormalities, and skeletal growth disorders.
The occurrence of vitamin A deficiency is linked both to insufficient dietary supply and to specific risk factors that hinder its absorption or increase the body’s requirement. It’s most often seen in developing countries where animal products and carotenoid-rich fruits and vegetables are scarce. High-risk groups include infants and young children, pregnant and breastfeeding women, the elderly, and those with limited access to a variety of foods. The risk increases in patients with digestive diseases leading to fat malabsorption (including celiac disease, pancreatic diseases, chronic liver and biliary disorders, and short bowel syndrome) since vitamin A is absorbed and stored only with properly functioning digestive processes. Those with metabolic disorders, chronic alcoholism, and patients after bariatric surgery are also at greater risk. Strict elimination diets and long-term poorly planned vegan and vegetarian diets that do not provide enough beta-carotene–rich vegetables, especially if no fats are included as vitamin carriers, greatly increase deficiency risk. Demand for vitamin A also rises during rapid physical growth (adolescence), infection, inflammation, or intense physical activity. Additionally, some medications (e.g., those reducing fat absorption or used for chronic gastrointestinal diseases) can impair vitamin balance, requiring regular monitoring and supplementation if needed. All these factors mean an appropriate diet, preventive care, and health monitoring are crucial for preventing the consequences of vitamin A deficiency, especially in high-risk groups.
Excess Vitamin A – Health Effects and Risks
Excessive intake of vitamin A, especially from animal-based retinoids (retinol and its esters), can lead to serious health effects. This phenomenon is known as hypervitaminosis A and is particularly dangerous because vitamin A is stored in the liver and cannot be easily eliminated from the body. Overdose cases happen primarily because of prolonged supplement use or use of retinoid-based medications, and rarely due to very retinol-rich diets. Chronic hypervitaminosis A manifests as headaches, chronic fatigue, dry and itchy skin, hair loss, cracked lips, bone and joint pain, and an enlarged liver and spleen. In children, excess can cause impaired growth, hydrocephalus, irritability, and even developmental delays. In severe cases, hypervitaminosis leads to liver damage, osteoporosis, neurological disorders, and in pregnancy can cause fetal malformations, including skeletal deformities, cleft palate, and heart defects. Excess retinoids negatively affect calcium and vitamin D metabolism, increasing the risk of osteoporosis and bone fractures even in young people. Acute overdose causes symptoms such as nausea, vomiting, dizziness, vision disturbances, elevated body temperature, or seizures. Importantly, sources of vitamin A as beta-carotene (plant-derived provitamin A) are much less toxic—excess carotenoids usually only cause a yellowish skin discoloration (carotenoderma), which resolves after lowering intake and does not cause permanent health damage.
Those especially vulnerable to vitamin A toxicity include people taking supplements without medical supervision, children, pregnant women, and people with liver or kidney diseases. Supplement safety should always be consulted with a doctor, as upper tolerable limits for retinol intake are relatively low—about 3000 µg (10,000 IU) per day for adults. Chronic excess can cause accumulation of toxic metabolites in the liver, leading to liver damage. Retinoid medications for dermatological and skin conditions also require strict medical oversight due to teratogenic risk and systemic complications. Excess vitamin A can impair thyroid function, disrupt menstrual cycles, and contribute to depression and concentration problems. Hypervitaminosis is particularly dangerous because it can be hard to diagnose quickly, with symptoms mistaken for other conditions, so an individualized approach to supplementation is always vital. High consumption of animal products, especially liver, is not recommended for chronically ill, women planning pregnancy, or the elderly with lowered metabolism. Nutrition education, awareness of the risks, and regular health monitoring are essential to preventing excess vitamin A in the body.
Supplementation and Prevention – How to Maintain an Appropriate Level of Vitamin A?
A well-balanced diet tailored to individual needs is the foundation for maintaining proper vitamin A levels. The recommended daily vitamin A intake varies by age, sex, physiological state, and physical activity—on average, about 700 µg retinol for adult women and 900 µg for men. Both retinol and carotenoid sources should be in the diet: liver, egg yolks, full-fat dairy, colorful vegetables (carrots, bell peppers, spinach, sweet potatoes), fruits (apricots, mango), and vitamin A–fortified products. Remember, proper absorption of this vitamin depends on the presence of fats in meals—so combine beta-carotene–rich vegetables and fruits with a bit of healthy fat, such as olive oil, canola oil, or nuts. Regular intake of such foods, proper meal balance, and dietary variety are the basis of effective vitamin A deficiency prevention. The need for this vitamin increases during periods of rapid growth, pregnancy, lactation, recovery, and some chronic illnesses. In these cases, pay more attention to consuming vitamin A–rich foods and regularly monitor blood levels—especially in those at risk for deficiency (children, seniors, pregnant and lactating women, those on elimination diets such as vegans or people with lactose intolerance, and patients with fat absorption disorders due to liver, pancreas, or digestive diseases).
For people unable to meet their vitamin A needs from food alone (due to elimination diets, absorption problems, or higher requirements), supplementation under medical supervision is possible. Various preparations exist—both retinol-based and beta-carotene-based, as well as multivitamin complexes. It is vital to tailor supplementation to individual needs and health status—excess, especially of retinol, is toxic and can cause severe hypervitaminosis. Therefore, supplementation requires systematic vitamin A level monitoring, regular lab tests, and consultations with a doctor or dietitian. Optimal health prevention relies on mindful supplement use and avoiding unnecessary intake, since a balanced diet is usually enough to cover daily vitamin A needs. Modern preventive strategies also include consumer education about deficiency and excess warning signs, principles of healthy eating, and the role fats play in vitamin A absorption. Making fortified foods more accessible, especially in at-risk populations, and implementing nutrition programs in schools and care institutions are also important. Proper prevention, monitoring, and education are the foundation for effective public health and for minimizing both deficiency and excess of vitamin A.
Summary
Vitamin A plays a key role in maintaining healthy eyes, skin, and an immune system. Adequate levels ensure the body’s proper function and protection against deficiency-related diseases. An appropriate diet rich in both animal and plant sources effectively meets vitamin A needs—yet both deficiency and excess can be harmful. Ensuring a varied diet, prevention, and consulting a physician regarding supplementation are the best ways to maintain balance. Take care to include the right amount of vitamin A in your daily diet!
