Nutrient Fact Sheets
|
March 24, 2023

Vitamin A 101: Health Benefits, Testing, & Top Foods

Medically Reviewed by
Updated On
September 17, 2024

Vitamin A deficiency is the leading preventable cause of childhood blindness worldwide. Vitamin A is also called the "anti-infective vitamin" as it’s critically important for immune function. In addition to its effects on vision and immune function, vitamin A plays a role in other processes in the body. This article will discuss vitamin A's role in the body, how to test vitamin A levels, and how to ensure you're getting proper amounts in your diet. 

[signup]

What is Vitamin A?

Vitamin A is an umbrella term encompassing a group of molecules called retinoids. Retinol, retinal, and retinoic acid are the active retinoids found in the body. These fat-soluble molecules are derived from two main sources: preformed vitamin A and provitamin A carotenoids. Preformed vitamin A includes retinol and retinyl esters and is primarily found in animal products. Provitamin A carotenoids are found in plants, often giving them their color, and are converted into retinoids in the intestines. Beta-carotene, alpha-carotene, and beta-cryptoxanthin are the most common provitamin A carotenoids. Most vitamin A consumption is in the form of preformed vitamin A. 

What is Vitamin A's Role in The Body?

Vitamin A plays an essential role in eyesight, regulation of gene expression, immunity, development, and red blood cell production.

Eyesight

Vitamin A is essential for proper functioning in many parts of the eye, including the cornea, conjunctival membranes, and retina. 

Gene Expression

Vitamin A has various roles in gene expression. Retinoic acid has the potential to modulate over 500 different genes, including vitamin D, steroids (including sex hormones), thyroid hormones, and more. Genes in the eye, muscle, and white adipose tissue seem responsive to retinol. Finally, retinal has a modulatory role in lipid, or fat, metabolism. 

Immunity

Retinoic acid is found in the mucosal lining of the pulmonary system, digestive tract, and urinary tract. This lining is the body's first defense against foreign invaders. Retinoic acid is also found in the lymph nodes of the areas mentioned above.

Development

Vitamin A is essential for the formation of various organs, including the heart, lungs, and eyes. Additionally, vitamin A is important for the development of limbs. 

Red Blood Cell Production

Red blood cells (RBCs) are responsible for carrying oxygen throughout the body. Vitamin A has the ability to transfer iron into the developing red blood cell, where it will be utilized to make hemoglobin. Hemoglobin is where oxygen is carried on the RBC. 

How to Test Vitamin A Levels

Vitamin A deficiencies are rare in the United States. However, they still occur in areas where consumption of provitamin A and preformed vitamin A foods are low, primarily due to the population's diet or low socioeconomic status. Vitamin A deficiency rates are 44% and 48% in South Asia and sub-Saharan Africa, respectively. Children and pregnant women in the middle to lower economic areas seem to be most at risk for vitamin A deficiencies. Populations at risk for lower levels of vitamin A include preterm babies, people with cystic fibrosis and gastrointestinal disorders, and certain populations that live in middle to low-income areas, including infants, children, and pregnant and lactating women. 

Xerophthalmia is the most common sign of a vitamin A deficiency. Xerophthalmia is a condition of the eye that occurs when vitamin A stores are low and begins with difficulty seeing at night but can eventually lead to permanent blindness. For children, vitamin A deficiency is one of the most common causes of preventable blindness.

Vitamin A deficiency increases the risk of poor outcomes for children against viral diseases, specifically measles and infectious diarrhea. Chronic vitamin A deficiency may lead to lung developmental problems, pneumonia, and other respiratory diseases. People with chronic vitamin A deficiency are also at an increased risk for anemia and death. 

Hypervitaminosis A, or vitamin A toxicity, if chronic, can lead to symptoms of fatigue, depression, joint and muscle pain, and dry skin. Elevated liver enzymes will be seen on blood work as vitamin A is stored in the liver and thus can damage it at high levels. Acute hypervitaminosis A, occurring days to weeks after an excessive intake of vitamin A, can cause nausea, dizziness, blurred vision, severe headaches, muscle aches, and balance issues. Severe cases of acute hypervitaminosis A can cause increased brain pressure and may lead to drowsiness, coma, and death. High levels of vitamin A can be achieved through supplementation and certain medications. 

Pregnant women are often advised to avoid Vitamin A supplements as taking higher amounts of preformed vitamin A can lead to congenital birth defects, including malformations of the skull, eye, lungs, and heart. 

Beta-carotene consumption does not seem to carry the same risk of preformed vitamin A. Excessive intake of beta-carotene may cause carotenodermia, a condition where the skin turns orange. This condition is reversible once the person stops consuming beta-carotene. However, there is evidence that excessive beta-carotene supplementation in male smokers may increase lung cancer risk and mortality. Additionally, a study assessing beta carotene paired with retinyl palmitate in males who currently or formerly smoked and some men who have been exposed to asbestos can increase the risk and mortality of lung cancer.

How to Make Sure You Are Getting Enough Vitamin A in Your Diet 

The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine created dietary recommendations for vitamins and minerals called Dietary Reference Intakes (DRIs). One such DRI is the Recommended Daily Allowance or the amount of a vitamin or mineral that is sufficient to reach nutritional adequacy in most healthy adults. For Vitamin A, RDA units are in retinol activity equivalents (RAEs), encompassing both retinol and the provitamin A carotenoids, as the carotenoids will eventually be converted into retinol. One microgram (mcg) RAE equals one mcg of retinol, two mcg beta-carotene from supplements, 12 mcg beta-carotene from foods, 24 mcg alpha-carotene, or 24 mcg beta-cryptoxanthin.

Vitamin A RAE

Requirements for pregnant and lactating women often differ from the general population due to increased nutritional demands. The RAE for pregnant women aged 14-18 is 750 mcg, and 770 mcg RAE for 19+ years old. For lactating women, the RAE is 1,200 mcg for 14-18 year-olds and 1,300 mcg RAE for 19+ year-olds. 

For those under one year, insufficient evidence to form RDAs has led to the formation of Adequate Intakes (AIs). AIs are only created when there is not enough evidence to form RDAs. AIs are levels assumed to meet nutritional requirements for a given population. The AI for birth to six months is 400 mcg RAE, and for seven to 12 months is 500 mcg RAE for both males and females. 

Vitamin A can be sourced from food and supplements.

High Food Sources of Vitamin A

It's important to note that the Food and Drug Administration (FDA), the organization responsible for food label regulation, does not require a product to list vitamin A content unless it has been added to the food. Foods at 20% or higher are considered high sources of vitamin A. 

Supplements

Vitamin A is available as a stand-alone supplement and is usually in multivitamins. The most common forms of vitamin A seen in supplements are retinyl palmitate, and retinyl acetate, with an absorption rate between 70-90%, and beta carotene, with an absorption rate of 8.7 to 65%. 

[signup]

Health Benefits of Vitamin A

Vitamin A is an essential vitamin from conception to the end of life. With direct effects on the immune system, vision, gene expression, and oxygenation of the tissues, vitamin A plays a significant role in health quality. Thus, vitamin A testing can help assess healthy bodily functioning. 

Vitamin A deficiency is a leading cause of preventable childhood vision issues worldwide. Vitamin A is sometimes referred to as the "anti-infective vitamin" due to its important role in supporting immune function. In addition to its effects on vision and immune function, vitamin A contributes to other processes in the body. This article will discuss vitamin A's role in the body, how to test vitamin A levels, and how to ensure you're getting proper amounts in your diet. 

[signup]

What is Vitamin A?

Vitamin A is an umbrella term encompassing a group of molecules called retinoids. Retinol, retinal, and retinoic acid are the active retinoids found in the body. These fat-soluble molecules are derived from two main sources: preformed vitamin A and provitamin A carotenoids. Preformed vitamin A includes retinol and retinyl esters and is primarily found in animal products. Provitamin A carotenoids are found in plants, often giving them their color, and are converted into retinoids in the intestines. Beta-carotene, alpha-carotene, and beta-cryptoxanthin are the most common provitamin A carotenoids. Most vitamin A consumption is in the form of preformed vitamin A. 

What is Vitamin A's Role in The Body?

Vitamin A plays an essential role in supporting eyesight, regulation of gene expression, immune function, development, and red blood cell production.

Eyesight

Vitamin A is important for the proper functioning of many parts of the eye, including the cornea, conjunctival membranes, and retina. 

Gene Expression

Vitamin A has various roles in gene expression. Retinoic acid has the potential to modulate over 500 different genes, including those related to vitamin D, steroids (including sex hormones), thyroid hormones, and more. Genes in the eye, muscle, and white adipose tissue seem responsive to retinol. Finally, retinal has a modulatory role in lipid, or fat, metabolism. 

Immunity

Retinoic acid is found in the mucosal lining of the pulmonary system, digestive tract, and urinary tract. This lining is part of the body's defense against foreign invaders. Retinoic acid is also found in the lymph nodes of the areas mentioned above.

Development

Vitamin A is important for the formation of various organs, including the heart, lungs, and eyes. Additionally, vitamin A supports the development of limbs. 

Red Blood Cell Production

Red blood cells (RBCs) are responsible for carrying oxygen throughout the body. Vitamin A helps transfer iron into the developing red blood cell, where it will be utilized to make hemoglobin. Hemoglobin is where oxygen is carried on the RBC. 

How to Test Vitamin A Levels

Vitamin A deficiencies are rare in the United States. However, they still occur in areas where consumption of provitamin A and preformed vitamin A foods are low, primarily due to the population's diet or low socioeconomic status. Vitamin A deficiency rates are 44% and 48% in South Asia and sub-Saharan Africa, respectively. Children and pregnant women in the middle to lower economic areas seem to be most at risk for vitamin A deficiencies. Populations at risk for lower levels of vitamin A include preterm babies, people with cystic fibrosis and gastrointestinal disorders, and certain populations that live in middle to low-income areas, including infants, children, and pregnant and lactating women. 

Xerophthalmia is a common sign of a vitamin A deficiency. Xerophthalmia is a condition of the eye that occurs when vitamin A stores are low and begins with difficulty seeing at night but can eventually lead to vision problems. For children, vitamin A deficiency is one of the most common causes of preventable vision issues.

Vitamin A deficiency may increase the risk of poor outcomes for children against viral diseases, specifically measles and infectious diarrhea. Chronic vitamin A deficiency may contribute to lung developmental problems, pneumonia, and other respiratory issues. People with chronic vitamin A deficiency may also be at an increased risk for anemia and other health concerns. 

Hypervitaminosis A, or vitamin A toxicity, if chronic, can lead to symptoms of fatigue, mood changes, joint and muscle discomfort, and dry skin. Elevated liver enzymes may be seen on blood work as vitamin A is stored in the liver and thus can affect it at high levels. Acute hypervitaminosis A, occurring days to weeks after an excessive intake of vitamin A, can cause nausea, dizziness, blurred vision, severe headaches, muscle aches, and balance issues. Severe cases of acute hypervitaminosis A can cause increased brain pressure and may lead to drowsiness, coma, and other serious health issues. High levels of vitamin A can be achieved through supplementation and certain medications. 

Pregnant women are often advised to avoid Vitamin A supplements as taking higher amounts of preformed vitamin A can lead to congenital birth defects, including malformations of the skull, eye, lungs, and heart. 

Beta-carotene consumption does not seem to carry the same risk as preformed vitamin A. Excessive intake of beta-carotene may cause carotenodermia, a condition where the skin turns orange. This condition is reversible once the person stops consuming beta-carotene. However, there is evidence that excessive beta-carotene supplementation in male smokers may increase lung cancer risk and mortality. Additionally, a study assessing beta carotene paired with retinyl palmitate in males who currently or formerly smoked and some men who have been exposed to asbestos can increase the risk and mortality of lung cancer.

How to Make Sure You Are Getting Enough Vitamin A in Your Diet 

The Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine created dietary recommendations for vitamins and minerals called Dietary Reference Intakes (DRIs). One such DRI is the Recommended Daily Allowance or the amount of a vitamin or mineral that is sufficient to reach nutritional adequacy in most healthy adults. For Vitamin A, RDA units are in retinol activity equivalents (RAEs), encompassing both retinol and the provitamin A carotenoids, as the carotenoids will eventually be converted into retinol. One microgram (mcg) RAE equals one mcg of retinol, two mcg beta-carotene from supplements, 12 mcg beta-carotene from foods, 24 mcg alpha-carotene, or 24 mcg beta-cryptoxanthin.

Vitamin A RAE

Requirements for pregnant and lactating women often differ from the general population due to increased nutritional demands. The RAE for pregnant women aged 14-18 is 750 mcg, and 770 mcg RAE for 19+ years old. For lactating women, the RAE is 1,200 mcg for 14-18 year-olds and 1,300 mcg RAE for 19+ year-olds. 

For those under one year, insufficient evidence to form RDAs has led to the formation of Adequate Intakes (AIs). AIs are only created when there is not enough evidence to form RDAs. AIs are levels assumed to meet nutritional requirements for a given population. The AI for birth to six months is 400 mcg RAE, and for seven to 12 months is 500 mcg RAE for both males and females. 

Vitamin A can be sourced from food and supplements.

High Food Sources of Vitamin A

It's important to note that the Food and Drug Administration (FDA), the organization responsible for food label regulation, does not require a product to list vitamin A content unless it has been added to the food. Foods at 20% or higher are considered high sources of vitamin A. 

Supplements

Vitamin A is available as a stand-alone supplement and is usually in multivitamins. The most common forms of vitamin A seen in supplements are retinyl palmitate, and retinyl acetate, with an absorption rate between 70-90%, and beta carotene, with an absorption rate of 8.7 to 65%. 

[signup]

Health Benefits of Vitamin A

Vitamin A is an essential vitamin from conception to the end of life. With roles in supporting the immune system, vision, gene expression, and oxygenation of the tissues, vitamin A contributes significantly to overall health quality. Thus, vitamin A testing can help assess healthy bodily functioning. 

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.

Learn more

No items found.

Lab Tests in This Article

Order from 30+ labs in 20 seconds (DUTCH, Mosaic, Genova & More!)
We make ordering quick and painless — and best of all, it's free for practitioners.

Latest Articles

View more on Nutrient Fact Sheets
Subscribe to the Magazine for free
Subscribe for free to keep reading! If you are already subscribed, enter your email address to log back in.
Thanks for subscribing!
Oops! Something went wrong while submitting the form.
Are you a healthcare practitioner?
Thanks for subscribing!
Oops! Something went wrong while submitting the form.
Subscribe to the Magazine for free to keep reading!
Subscribe for free to keep reading, If you are already subscribed, enter your email address to log back in.
Thanks for subscribing!
Oops! Something went wrong while submitting the form.
Are you a healthcare practitioner?
Thanks for subscribing!
Oops! Something went wrong while submitting the form.
Trusted Source
Rupa Health
Medical Education Platform
Visit Source
Visit Source
American Cancer Society
Foundation for Cancer Research
Visit Source
Visit Source
National Library of Medicine
Government Authority
Visit Source
Visit Source
Journal of The American College of Radiology
Peer Reviewed Journal
Visit Source
Visit Source
National Cancer Institute
Government Authority
Visit Source
Visit Source
World Health Organization (WHO)
Government Authority
Visit Source
Visit Source
The Journal of Pediatrics
Peer Reviewed Journal
Visit Source
Visit Source
CDC
Government Authority
Visit Source
Visit Source
Office of Dietary Supplements
Government Authority
Visit Source
Visit Source
National Heart Lung and Blood Institute
Government Authority
Visit Source
Visit Source
National Institutes of Health
Government Authority
Visit Source
Visit Source
Clinical Infectious Diseases
Peer Reviewed Journal
Visit Source
Visit Source
Brain
Peer Reviewed Journal
Visit Source
Visit Source
The Journal of Rheumatology
Peer Reviewed Journal
Visit Source
Visit Source
Journal of the National Cancer Institute (JNCI)
Peer Reviewed Journal
Visit Source
Visit Source
Journal of Cardiovascular Magnetic Resonance
Peer Reviewed Journal
Visit Source
Visit Source
Hepatology
Peer Reviewed Journal
Visit Source
Visit Source
The American Journal of Clinical Nutrition
Peer Reviewed Journal
Visit Source
Visit Source
The Journal of Bone and Joint Surgery
Peer Reviewed Journal
Visit Source
Visit Source
Kidney International
Peer Reviewed Journal
Visit Source
Visit Source
The Journal of Allergy and Clinical Immunology
Peer Reviewed Journal
Visit Source
Visit Source
Annals of Surgery
Peer Reviewed Journal
Visit Source
Visit Source
Chest
Peer Reviewed Journal
Visit Source
Visit Source
The Journal of Neurology, Neurosurgery & Psychiatry
Peer Reviewed Journal
Visit Source
Visit Source
Blood
Peer Reviewed Journal
Visit Source
Visit Source
Gastroenterology
Peer Reviewed Journal
Visit Source
Visit Source
The American Journal of Respiratory and Critical Care Medicine
Peer Reviewed Journal
Visit Source
Visit Source
The American Journal of Psychiatry
Peer Reviewed Journal
Visit Source
Visit Source
Diabetes Care
Peer Reviewed Journal
Visit Source
Visit Source
The Journal of the American College of Cardiology (JACC)
Peer Reviewed Journal
Visit Source
Visit Source
The Journal of Clinical Oncology (JCO)
Peer Reviewed Journal
Visit Source
Visit Source
Journal of Clinical Investigation (JCI)
Peer Reviewed Journal
Visit Source
Visit Source
Circulation
Peer Reviewed Journal
Visit Source
Visit Source
JAMA Internal Medicine
Peer Reviewed Journal
Visit Source
Visit Source
PLOS Medicine
Peer Reviewed Journal
Visit Source
Visit Source
Annals of Internal Medicine
Peer Reviewed Journal
Visit Source
Visit Source
Nature Medicine
Peer Reviewed Journal
Visit Source
Visit Source
The BMJ (British Medical Journal)
Peer Reviewed Journal
Visit Source
Visit Source
The Lancet
Peer Reviewed Journal
Visit Source
Visit Source
Journal of the American Medical Association (JAMA)
Peer Reviewed Journal
Visit Source
Visit Source
Pubmed
Comprehensive biomedical database
Visit Source
Visit Source
Harvard
Educational/Medical Institution
Visit Source
Visit Source
Cleveland Clinic
Educational/Medical Institution
Visit Source
Visit Source
Mayo Clinic
Educational/Medical Institution
Visit Source
Visit Source
The New England Journal of Medicine (NEJM)
Peer Reviewed Journal
Visit Source
Visit Source
Johns Hopkins
Educational/Medical Institution
Visit Source
Visit Source

Hey Practitioners! Ready to become a world class gut health expert? Join Jeannie Gorman, MS, CCN, for a Free Live Class that dives into how popular diets impact the gut microbiome, the clinical dietary needs of your gut, biomarkers to test to analyze gut health, and gain a clear understanding of the Doctor’s Data GI360™ profile. Register here.