RESEARCH STARTER

Vitamin A

Vitamin A is a fat-soluble nutrient essential for numerous bodily functions, including vision, immune system response, and tissue growth. It exists in two primary forms: preformed vitamin A (retinoids), found in animal products like dairy and meat, and provitamin A (carotenoids), found in colorful fruits and vegetables such as carrots and sweet potatoes. A balanced diet typically provides adequate vitamin A, though it can also be taken as supplements, including retinyl acetate, retinyl palmitate, and beta-carotene. While vitamin A is often praised for its health benefits—including potential roles in preventing conditions like poor vision, certain cancers, and skin issues—excessive intake can lead to serious health problems, such as impaired immunity and increased risks of fractures.

Deficiency in vitamin A is a significant global health issue, particularly in developing countries, leading to compromised immune systems and serious eye conditions, including night blindness and keratomalacia, which can cause blindness in children. Approximately one-third of children under five worldwide are affected by vitamin A deficiency, emphasizing the importance of dietary sources and nutritional interventions. Given its dual nature as both beneficial and potentially harmful, it is advisable for individuals considering vitamin A supplementation to consult healthcare professionals.

Full Article

Vitamin A is a general term classification given to a number of naturally occurring, fat-soluble nutrients that assist the body in performing a wide range of critical activities. It is particularly important for vision and immune system functions. Vitamin A is readily available from many sources, such as dairy products, some fish, and meat, as well as fruits and vegetables, and fortified breakfast cereals. A balanced diet typically supplies enough vitamin A for most people. It can also be taken as a dietary supplement, either standalone as retinyl acetate, retinyl palmitate, or beta-carotene, or as part of a multivitamin.

Because research has suggested vitamin A’s potential role in preventing, treating, or at least ameliorating conditions such as poor vision, infertility, chronic heart disease, acne, skin cancer and pancreatic cancer, depression, insomnia, and fatigue, the vitamin has been promoted in some contexts as something of an all-purpose wonder drug. Vitamin A is one of the most recommended nutrients for general health and maintenance of the body’s systems against the vulnerabilities and deteriorations associated with the otherwise normative processes of aging. However, the effects of vitamin A as a supplement are not fully understood or proven, and research continues to investigate the effects of vitamin A. Miracle claims such as overarching anti-cancer properties are not supported by scientific evidence. It has also been shown that high doses of some forms of vitamin A can have negative effects, and supplements can also interact with medications; anyone interested in taking a dietary supplement should consult a doctor.

Background

Broadly speaking, vitamin A falls into two classifications: preformed vitamin A and provitamin A. Preformed vitamin A, which includes substances known as retinoids, including retinol, are found in eggs, meat, cheeses, most fish (especially tuna and cod), processed dairy products (such as milk and cottage cheese), and poultry. Provitamin A, which includes several substances known as carotenoids, is found in most orange and yellow fruits and vegetables (carrots, sweet potatoes, chili peppers, pumpkins, grapefruits, and oranges) as well as in most dark green leafy vegetables (such as spinach and kale). In addition, vitamin A has been processed into a dietary supplement, most often marketed as retinyl acetate or beta-carotene. Nutritionists, however, are quick to point out that the wide accessibility of vitamin A in natural forms means that a healthy and varied diet will assure the body adequate amounts of usable vitamin A. The U.S. Food and Drug Administration (FDA) sets the daily value (DV) for vitamin A at 900 micrograms of retinol activity equivalents (RAE) for adults and children aged 4 years and older. Three average-sized carrots, for instance, provide that and more.

As nutrients, both classifications of vitamin A are directed by the body to widely different functions at the molecular level. The retinoids, for instance, are critical in red blood cell production and maintenance, although researchers are still working out the how and why. This means that retinoids help the body’s immune system respond quickly and effectively to imbalances caused by invading bacteria and viruses. They assist the body in tissue growth maintenance, particularly after injuries or surgery, and they assist in promoting fertility and improving the chances of pregnancy. Retinoids also promote effective and efficient food processing and digestive function. But perhaps the most widely known function of the retinoids stems from their promotion of vision acuity. There is truth in the old adage that eating carrots keeps vision strong. Retinoids help the retina produce rhodopsin, a pigment in rod cells. Those rod cells are particularly responsible for detecting muted light and for responding to sudden drops in available bright light. Vitamin A1 (retinol) is essential for maintaining normal night vision and for treating xerophthalmia (an inability to see in low light that can lead to blindness). Retinoids are also used, both topically and orally, to treat skin conditions, including psoriasis and acne. Retinoids have seen some success in the treatment of precancerous skin conditions, such as actinic keratosis (a skin condition caused by prolonged exposure to ultraviolet radiation). It has also been used to treat cutaneous neoplasms, inhibit tumor growth, and encourage cell maturation. Further research is being conducted on the possibility of their use in other skin cancer treatments.

Carotenoids, on the other hand, can act as antioxidants, which are believed to potentially assist cells in halting and even stopping the damage done long-term by cellular exposure to oxygen. When a molecule suddenly loses an electron, it becomes what is called a free radical. Inherently unstable, free radicals seek any available electron to return it to stability and integrity, most often by simply stealing an electron from any readily available oxygen molecules in the cell. That triggers a kind of domino effect where the robbed cell now needs an electron, thus creating a sustained, long-term chain of cellular destruction. This helps account for any of a wide variety of slow-motion catastrophic ailments, such as cancers, and diabetes, Alzheimer’s disease and other dementias, aging (specifically the skin folds characteristic with aging), and blindness. As an antioxidant, carotenoids (a form of vitamin A) help neutralize free radicals, including by donating electrons or hydrogen atoms to stabilize them, thus halting the destructive interaction with oxygen. Research has not entirely agreed on what impact vitamin A has—whether it retards the process, controls it, or entirely halts it—but the presence of antioxidants is thought to help the body’s molecular structures maintain their efficiency and their structural integrity.

Overview

Because vitamin A appears to be such a boon for the body, consumers are often tempted to take amounts far exceeding recommended dosages as a way to ward off the effects of aging or to prevent the onset of cancer. Ironically, excessive intake can actually create significant problems. The National Institutes of Health (NIH) and the National Academy of Medicine set the tolerable upper intake level (UL) for adults at 3,000 micrograms of preformed vitamin A (retinol) per day. Too much vitamin A has been shown to actually usurp the body’s normal immune system function. Vitamin A in supplement form has not been consistently shown to prevent or fight cancer, and some studies have even suggested that excess beta-carotene supplements increase the risk of lung cancer in smokers. Excess vitamin A intake has also been linked to an increase in bone fractures, particularly hip fractures in the elderly. Additionally, vitamin A has been implicated in birth defects in the babies of mothers who consumed excessive amounts.

Another potential issue with vitamin A overconsumption is that most of the retinoid variations are found in foods that are high in saturated fats and cholesterol. These sources pose their own health risks. Fortunately, with rare exceptions, the body is capable of converting carotenoids into retinoids. Body systems impaired by genetic deficiencies and disorders, poor diet or malnutrition, those regularly exposed to industrial pollutants and chemical particulates, or those compromised by massive infectious diseases or excessive alcohol intake may struggle to complete the conversion efficiently.

Vitamin A Deficiency

Vitamin A is frequently among those food supplements most administered in diet programs that target developing nations. In developed countries, diet and nutrition are generally adequate and food products are readily available. In low- and middle-income countries, where food supplies are often compromised by catastrophic weather conditions, inadequate or inefficient agricultural processes, or political or military disruption, vitamin A deficiencies have been linked to widespread viral infectious disease outbreaks (particularly measles), as the lack of vitamin A weakens the immune system. It also causes deficiencies in the eyes, including night blindness, the whites of the eyes becoming dry and thick, and a condition known as keratomalacia. Keratomalacia, if untreated, leads to the cornea becoming opaque and is a leading cause of blindness in these countries, especially in children. The skin can also become dry, damaged, and more prone to infection. A lack of vitamin A during pregnancy can increase the risk of maternal mortality. Because these conditions are largely preventable through diet, it gives special urgency to international relief efforts addressed particularly to children. Global health programs led by the World Health Organization recommend and support the distribution of vitamin A supplements to children aged 6 to 59 months in high-risk regions to reduce mortality and prevent blindness.

Vitamin A deficiency was estimated to affect about 14 percent of children under five years in low- and middle-income countries in 2019.


Bibliography

Ahmad, Shaikh Meshbahuddin, et al. “The Effect of Postpartum Vitamin A Supplementation on Breast Milk Immune Regulators and Infant Immune Functions: Study Protocol of a Randomized, Controlled Trial.” Trials, vol. 16, no. 1, Mar. 2015, doi:10.1186/s13063-015-0654-9. Accessed 25 Mar. 2026.

Higdon, Jane. “Vitamin A.” Linus Pauling Institute Micronutrient Information Center, Oregon State University, Jan. 2024, lpi.oregonstate.edu/mic/vitamins/vitamin-A. Accessed 25 Mar. 2026.

Kubala, Jillian. “Vitamin A: Benefits, Deficiency, Toxicity and More.” Healthline, 24 Apr. 2023, www.healthline.com/nutrition/vitamin-a. Accessed 25 Mar. 2026.

“Micronutrients.” World Health Organization, www.who.int/nutrition/topics/vad/en/. Accessed 25 Mar. 2026.

Silverman, Harold, et al. The Vitamin Book. Bantam, 2002.

Sommer, Alfred. “Vitamin a Deficiency and Clinical Disease: An Historical Overview.” The Journal of Nutrition, vol. 138, no. 10, Oct. 2008, pp. 1835–39, doi:10.1093/jn/138.10.1835. Accessed 25 Mar. 2026.

Song, Peige, et al. “The Prevalence of Vitamin a Deficiency and Its Public Health Significance in Children in Low- and Middle-Income Countries: A Systematic Review and Modelling Analysis.” Journal of Global Health, vol. 13, no. PMC10416138, 11 Aug. 2023, article 04084, doi:10.7189/jogh.13.04084. Accessed 25 Mar. 2026.

Tang, Kevin, et al. “Evaluating Equity Dimensions of Infant and Child Vitamin A Supplementation Programmes Using Demographic and Health Surveys from 49 Countries.” BMJ Open, vol. 13, no. 3, 2023, art. No. e062387, bmjopen.bmj.com/content/13/3/e062387. Accessed 25 Mar. 2026.

“Vitamin A.” Mayo Clinic, 14 Sept. 2023, www.mayoclinic.org/drugs-supplements-vitamin-a/art-20365945. Accessed 25 Mar. 2026.

“Vitamin A.” MedlinePlus, U.S. National Library of Medicine, 21 Jan. 2025, medlineplus.gov/ency/article/002400.htm. Accessed 25 Mar. 2026.

“Vitamin A and Carotenoids.” Office of Dietary Supplements, National Institutes of Health, 10 Mar. 2025, ods.od.nih.gov/factsheets/VitaminA-Consumer/. Accessed 25 Mar. 2026.

Full Article

Vitamin A is a general term classification given to a number of naturally occurring, fat-soluble nutrients that assist the body in performing a wide range of critical activities. It is particularly important for vision and immune system functions. Vitamin A is readily available from many sources, such as dairy products, some fish, and meat, as well as fruits and vegetables, and fortified breakfast cereals. A balanced diet typically supplies enough vitamin A for most people. It can also be taken as a dietary supplement, either standalone as retinyl acetate, retinyl palmitate, or beta-carotene, or as part of a multivitamin.

Because research has suggested vitamin A’s potential role in preventing, treating, or at least ameliorating conditions such as poor vision, infertility, chronic heart disease, acne, skin cancer and pancreatic cancer, depression, insomnia, and fatigue, the vitamin has been promoted in some contexts as something of an all-purpose wonder drug. Vitamin A is one of the most recommended nutrients for general health and maintenance of the body’s systems against the vulnerabilities and deteriorations associated with the otherwise normative processes of aging. However, the effects of vitamin A as a supplement are not fully understood or proven, and research continues to investigate the effects of vitamin A. Miracle claims such as overarching anti-cancer properties are not supported by scientific evidence. It has also been shown that high doses of some forms of vitamin A can have negative effects, and supplements can also interact with medications; anyone interested in taking a dietary supplement should consult a doctor.

Background

Broadly speaking, vitamin A falls into two classifications: preformed vitamin A and provitamin A. Preformed vitamin A, which includes substances known as retinoids, including retinol, are found in eggs, meat, cheeses, most fish (especially tuna and cod), processed dairy products (such as milk and cottage cheese), and poultry. Provitamin A, which includes several substances known as carotenoids, is found in most orange and yellow fruits and vegetables (carrots, sweet potatoes, chili peppers, pumpkins, grapefruits, and oranges) as well as in most dark green leafy vegetables (such as spinach and kale). In addition, vitamin A has been processed into a dietary supplement, most often marketed as retinyl acetate or beta-carotene. Nutritionists, however, are quick to point out that the wide accessibility of vitamin A in natural forms means that a healthy and varied diet will assure the body adequate amounts of usable vitamin A. The U.S. Food and Drug Administration (FDA) sets the daily value (DV) for vitamin A at 900 micrograms of retinol activity equivalents (RAE) for adults and children aged 4 years and older. Three average-sized carrots, for instance, provide that and more.

As nutrients, both classifications of vitamin A are directed by the body to widely different functions at the molecular level. The retinoids, for instance, are critical in red blood cell production and maintenance, although researchers are still working out the how and why. This means that retinoids help the body’s immune system respond quickly and effectively to imbalances caused by invading bacteria and viruses. They assist the body in tissue growth maintenance, particularly after injuries or surgery, and they assist in promoting fertility and improving the chances of pregnancy. Retinoids also promote effective and efficient food processing and digestive function. But perhaps the most widely known function of the retinoids stems from their promotion of vision acuity. There is truth in the old adage that eating carrots keeps vision strong. Retinoids help the retina produce rhodopsin, a pigment in rod cells. Those rod cells are particularly responsible for detecting muted light and for responding to sudden drops in available bright light. Vitamin A1 (retinol) is essential for maintaining normal night vision and for treating xerophthalmia (an inability to see in low light that can lead to blindness). Retinoids are also used, both topically and orally, to treat skin conditions, including psoriasis and acne. Retinoids have seen some success in the treatment of precancerous skin conditions, such as actinic keratosis (a skin condition caused by prolonged exposure to ultraviolet radiation). It has also been used to treat cutaneous neoplasms, inhibit tumor growth, and encourage cell maturation. Further research is being conducted on the possibility of their use in other skin cancer treatments.

Carotenoids, on the other hand, can act as antioxidants, which are believed to potentially assist cells in halting and even stopping the damage done long-term by cellular exposure to oxygen. When a molecule suddenly loses an electron, it becomes what is called a free radical. Inherently unstable, free radicals seek any available electron to return it to stability and integrity, most often by simply stealing an electron from any readily available oxygen molecules in the cell. That triggers a kind of domino effect where the robbed cell now needs an electron, thus creating a sustained, long-term chain of cellular destruction. This helps account for any of a wide variety of slow-motion catastrophic ailments, such as cancers, and diabetes, Alzheimer’s disease and other dementias, aging (specifically the skin folds characteristic with aging), and blindness. As an antioxidant, carotenoids (a form of vitamin A) help neutralize free radicals, including by donating electrons or hydrogen atoms to stabilize them, thus halting the destructive interaction with oxygen. Research has not entirely agreed on what impact vitamin A has—whether it retards the process, controls it, or entirely halts it—but the presence of antioxidants is thought to help the body’s molecular structures maintain their efficiency and their structural integrity.

Overview

Because vitamin A appears to be such a boon for the body, consumers are often tempted to take amounts far exceeding recommended dosages as a way to ward off the effects of aging or to prevent the onset of cancer. Ironically, excessive intake can actually create significant problems. The National Institutes of Health (NIH) and the National Academy of Medicine set the tolerable upper intake level (UL) for adults at 3,000 micrograms of preformed vitamin A (retinol) per day. Too much vitamin A has been shown to actually usurp the body’s normal immune system function. Vitamin A in supplement form has not been consistently shown to prevent or fight cancer, and some studies have even suggested that excess beta-carotene supplements increase the risk of lung cancer in smokers. Excess vitamin A intake has also been linked to an increase in bone fractures, particularly hip fractures in the elderly. Additionally, vitamin A has been implicated in birth defects in the babies of mothers who consumed excessive amounts.

Another potential issue with vitamin A overconsumption is that most of the retinoid variations are found in foods that are high in saturated fats and cholesterol. These sources pose their own health risks. Fortunately, with rare exceptions, the body is capable of converting carotenoids into retinoids. Body systems impaired by genetic deficiencies and disorders, poor diet or malnutrition, those regularly exposed to industrial pollutants and chemical particulates, or those compromised by massive infectious diseases or excessive alcohol intake may struggle to complete the conversion efficiently.

Vitamin A Deficiency

Vitamin A is frequently among those food supplements most administered in diet programs that target developing nations. In developed countries, diet and nutrition are generally adequate and food products are readily available. In low- and middle-income countries, where food supplies are often compromised by catastrophic weather conditions, inadequate or inefficient agricultural processes, or political or military disruption, vitamin A deficiencies have been linked to widespread viral infectious disease outbreaks (particularly measles), as the lack of vitamin A weakens the immune system. It also causes deficiencies in the eyes, including night blindness, the whites of the eyes becoming dry and thick, and a condition known as keratomalacia. Keratomalacia, if untreated, leads to the cornea becoming opaque and is a leading cause of blindness in these countries, especially in children. The skin can also become dry, damaged, and more prone to infection. A lack of vitamin A during pregnancy can increase the risk of maternal mortality. Because these conditions are largely preventable through diet, it gives special urgency to international relief efforts addressed particularly to children. Global health programs led by the World Health Organization recommend and support the distribution of vitamin A supplements to children aged 6 to 59 months in high-risk regions to reduce mortality and prevent blindness.

Vitamin A deficiency was estimated to affect about 14 percent of children under five years in low- and middle-income countries in 2019.


Bibliography

Ahmad, Shaikh Meshbahuddin, et al. “The Effect of Postpartum Vitamin A Supplementation on Breast Milk Immune Regulators and Infant Immune Functions: Study Protocol of a Randomized, Controlled Trial.” Trials, vol. 16, no. 1, Mar. 2015, doi:10.1186/s13063-015-0654-9. Accessed 25 Mar. 2026.

Higdon, Jane. “Vitamin A.” Linus Pauling Institute Micronutrient Information Center, Oregon State University, Jan. 2024, lpi.oregonstate.edu/mic/vitamins/vitamin-A. Accessed 25 Mar. 2026.

Kubala, Jillian. “Vitamin A: Benefits, Deficiency, Toxicity and More.” Healthline, 24 Apr. 2023, www.healthline.com/nutrition/vitamin-a. Accessed 25 Mar. 2026.

“Micronutrients.” World Health Organization, www.who.int/nutrition/topics/vad/en/. Accessed 25 Mar. 2026.

Silverman, Harold, et al. The Vitamin Book. Bantam, 2002.

Sommer, Alfred. “Vitamin a Deficiency and Clinical Disease: An Historical Overview.” The Journal of Nutrition, vol. 138, no. 10, Oct. 2008, pp. 1835–39, doi:10.1093/jn/138.10.1835. Accessed 25 Mar. 2026.

Song, Peige, et al. “The Prevalence of Vitamin a Deficiency and Its Public Health Significance in Children in Low- and Middle-Income Countries: A Systematic Review and Modelling Analysis.” Journal of Global Health, vol. 13, no. PMC10416138, 11 Aug. 2023, article 04084, doi:10.7189/jogh.13.04084. Accessed 25 Mar. 2026.

Tang, Kevin, et al. “Evaluating Equity Dimensions of Infant and Child Vitamin A Supplementation Programmes Using Demographic and Health Surveys from 49 Countries.” BMJ Open, vol. 13, no. 3, 2023, art. No. e062387, bmjopen.bmj.com/content/13/3/e062387. Accessed 25 Mar. 2026.

“Vitamin A.” Mayo Clinic, 14 Sept. 2023, www.mayoclinic.org/drugs-supplements-vitamin-a/art-20365945. Accessed 25 Mar. 2026.

“Vitamin A.” MedlinePlus, U.S. National Library of Medicine, 21 Jan. 2025, medlineplus.gov/ency/article/002400.htm. Accessed 25 Mar. 2026.

“Vitamin A and Carotenoids.” Office of Dietary Supplements, National Institutes of Health, 10 Mar. 2025, ods.od.nih.gov/factsheets/VitaminA-Consumer/. Accessed 25 Mar. 2026.

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