Vitamin A refers to a group of compounds rather than to a single structure. These different forms all have vitamin A function in the body. Since these similar-acting vitamins were the first of many to be isolated and identified, the group was named “vitamin A” after the first letter of the alphabet.
It may not be a coincidence that vitamin A was among the first nutrients to be studied. Vitamin A has many roles in the body, making it a likely target for attention among doctors and scientists who noticed its possible functions. As you will see below, vitamin A is necessary for proper fetal growth and development, healthy eyes and skin, a strong immune system, and even in preventing iron deficiency anemia. Some forms even have antioxidant activities in your body.
Vitamin A is in many foods, including both animal-based foods and plant foods. Most people who eat a normal varied diet can get enough of this essential nutrient from foods alone, but some health conditions and procedures can increase your risk of deficiency.
You might want to consider vitamin A supplements if you think you are not getting quite enough from the best sources of vitamin A. Just make sure your doctor agrees that they are safe and may provide the particular benefits you are looking for before you choose a vitamin A supplement and start using it.
What is Vitamin A?
There is no specific discovery date for vitamin A, but its existence has been suspected for about 200 years. An article on the history of vitamin A published in the “Annals of Nutrition and Metabolism” explains that in 1816, the physiologist François Magendie found that both nutritionally deprived dogs and malnourished infants in Paris had similar symptoms. In the 1880s and later decades, various scientists hypothesized that milk and egg yolks contained a specific nutrient that was necessary for life. Between 1918 and 1932, a form of vitamin A was isolated and identified. Since then, the knowledge of vitamin A has only increased.
As it turns out, vitamin A is a fat-soluble vitamin, which explains the fact that it is found in the fatty portion of milk as well as egg yolks, which contain fat. It comes in multiple forms. Animal foods with vitamin A have forms that are known as preformed vitamin A. These forms of the vitamin are ready for your body to use for typical vitamin A functions. Retinol, retinal, and retinoic acid are forms of preformed vitamin A, and they are known as retinoids.
Plant-based foods have precursors to vitamin A that your body can use for retinoid activity after converting it. These precursors are known as provitamin A, and the group is known as the carotenoids. Carotenoids are separated into two categories: carotenes and xanthophylls. The most common carotenes are alpha-carotene and beta-carotene, while some of the xanthophylls include lycopene, lutein, and zeaxanthin, according to WH Foods.
Retinoic Activity Equivalents (RAE)
Preformed vitamin A has higher activity in your body than provitamin A. To help you figure out how much vitamin A you are really getting, scientists have developed a system using “retinoic activity equivalents,” or RAE. As the Linus Pauling Institute explains, a unit of preformed vitamin A, such as retinol, has 1 RAE. In comparison, a unit of beta-carotene from food has only 0.5 RAE. That is, when you get beta-carotene from food, it has half the activity of preformed vitamin A. When you get beta-carotene from supplements, you need 12 units of beta-carotene to get the vitamin A function in the body of a single unit of a retinoid.
When you read a nutrition label on a food and see the vitamin A content, you are really looking at the amount of vitamin A in that food from each form of vitamin A, whether retinoid, carotene, or xanthophyll.
What are the Benefits of Vitamin A?
Vitamin A has many functions in the body, ranging from before birth all the way through aging.
Benefit: Supporting Prenatal Development
If you are pregnant or planning to become pregnant, you probably have done a bit of research on nutrition to support a healthy pregnancy and baby. Folic acid may be the vitamin that comes up first in the search engines, but vitamin A is just as important in proper development.
Vitamin A is associated with organ development. The fetus needs it for organs such as the heart, lungs, eyes, and ears, as well as the arms and legs. Deficiency of vitamin A in the mother can cause birth defects. If you are not sure about your vitamin A status, you should ask your doctor about vitamin A pills and dosage. In this case, getting too much can be as dangerous as getting too little.
Benefit: Promoting a Stronger Immune System
Many of the functions of vitamin A are related to your immune system. Vitamin A stimulates certain immune cells to be able to do their specialized jobs in targeting antigens, or potentially infectious or harmful agents. Vitamin A is especially active in the barriers of your body, such as the skin, and the lining of your airways and digestive tract. These barriers help keep germs out.
The most severe effects of vitamin A deficiency are in developing countries, where children who are infected with diseases such as measles can have a higher risk of death because they are often deficient in nutrients such as vitamin A. While few people in the U.S. are exposed to these diseases or are so severely malnourished, it is still a good idea to get enough food with vitamin A to keep your immune system working as well as it can.
Benefit: Supporting Healthy Vision
If there is one vitamin A function that almost everyone thinks of first, it is the function of allowing your eyes to work well. The form of preformed vitamin A known as retinol is a star player in the visual cycle.
When light hits your eyes, photoreceptor cells known as rods and cones detect the light. There is a cascade of events involving retinol changing into different forms of the vitamin. The result is that your rod and cone cells are able to send a signal to your brain regarding the light they saw. Then your brain interprets the signal as an image.
Mild vitamin A deficiency can lead to night blindness, or nyctalopia. This is the earliest sign of vitamin A deficiency that you are likely to see. It is reversible. However, if it is not treated, you can end up with progressive scarring of the eye tissue and eventual blindness, which is not reversible. While rare in the United States, severe vitamin A deficiency is the leading cause of preventable blindness worldwide.
Benefit: Improving Skin Health
All kinds of vitamin A supplements are on the market, and you have probably seen many ads promising they can improve skin health. It is easy to see how these claims came about, since vitamin A has so many important roles in keeping skin healthy. The Linus Pauling Institute explains how vitamin A may both prevent and treat certain types of skin damage, especially those related to exposure to ultraviolet (UV) radiation from the sun.
When you are in the sun for a long time, your skin might undergo photoaging. Over time, you might see signs such as large or small wrinkles, small blood vessels known as telangiectasia, rough skin, increased freckles, and hyperpigmentation, or darker skin than normal. These changes can happen in part because of the way UV radiation can reduce your skin’s ability to produce collagen, which keeps your skin looking young and strong.
Vitamin A may help prevent photoaging, in a process known as photoprotection, as well as reverse some of its effects. Since the skin is actually receptive to vitamin A, topical creams can be an effective way of delivering vitamin A to your skin.
If you have experienced acne, you probably have spent some time searching for an effective treatment. Vitamin A may be able to help. A topical cream may reduce symptoms if you have mild to moderate acne, while your doctor might suggest a prescription formulation if your acne is severe.
Vitamin A has another possible benefit for your skin. Since it is involved in your immune response and wound healing, a deficiency can lead to delayed wound healing. Vitamin A pills may help reverse this effect.
Benefit: Antioxidant Capabilities
Oxidation describes certain chemical reactions that can lead to damage to your body’s cells. Oxidation can occur when certain chemicals, such as free radicals, are present in your body. Vitamin A can act as an antioxidant to prevent these harmful reactions. Retinol, for example, may help protect your eyes from oxidation.
Vitamin A antioxidant roles could help explain some of the vitamin’s links to lower risks of certain disease. People who eat more vegetables and fruits with vitamin A may have a lower risk of developing age-related macular degeneration, heart disease, and cataracts. This may be due to the antioxidant activity of beta-carotene in fruits and vegetables.
Benefit: Supporting Healthy Red Blood Cells
Vitamin A is necessary for healthy erythropoiesis, or the production of healthy red blood cells in your body. For one thing, vitamin A allows for your stem cells to develop into specialized red blood cells.
For another, vitamin A is closely tied to your body’s use of iron, which is the mineral in red blood cells that carries oxygen for delivery to the cells throughout your body. Vitamin A allows iron to be taken from the liver and used in red blood cell production. It also can help prevent iron deficiency anemia or alleviate it, according to an article in the “European Journal of Clinical Nutrition.”
Which are the Foods High in Vitamin A?
Animal based foods and plant derived foods can both be high in different forms of vitamin A. Animal foods with preformed vitamin A include beef liver, cod liver oil, and dairy products such as butter, whole milk, and yogurt. Tuna is also a good source of vitamin A.
Orange fruits and vegetables are some of the best sources of vitamin A. They get their orange color from beta-carotene, which is actually a pigment in addition to being a nutrient. Some of the familiar vegetables that are excellent sources are carrots, sweet potatoes, winter squash, and pumpkin. Good fruit sources include mangoes, cantaloupe, and apricots.
Orange fruits and vegetables are not the only good plant-based sources of vitamin A. Leafy greens such as spinach, kale, and collard greens are rich in vitamin A. An extra benefit of getting vitamin A from fruits and vegetables is the extra nutrition you get, such as vitamin C, dietary fiber, and potassium.
Since vitamin A is a fat-soluble vitamin, your body will be able to absorb more of it from a meal or snack if you also include some fat with it. When possible, stick to healthy fat sources such as olive oil, nuts, and peanuts. Examples of healthy ways to get vitamin A include eating sweet potatoes roasted with olive oil, trail mix with nuts and dried apricots and papaya, and carrots with peanut butter. The animal-based food sources of vitamin A tend to be higher in fat already, and you are probably going to be able to absorb their vitamin A fairly well.
How Much Vitamin A Do You Need?
The recommended dietary allowance, or RDA, for a nutrient is the average daily amount of that nutrient that is likely to meet your needs. The RDA for vitamin A is 700 RAE for women, and 900 RAE for men. Your vitamin A recommended daily intake increases if you are pregnant or are breast-feeding.
Who is at Risk of Vitamin A Deficiency?
You are at risk of vitamin A deficiency if you do not get enough foods that have a high vitamin A content. This is possible if you avoid most fruits and vegetables, do not eat animal products such as meat, fish, and dairy, and do not get vitamin A from fortified foods. However, a severe deficiency is unlikely if you eat a fairly well balanced diet that includes many healthy foods.
The people in the United States who are at highest risk for vitamin A deficiency are people who have trouble absorbing fat, which leads to trouble absorbing this fat-soluble vitamin. You might have trouble absorbing dietary fat if you have a type of inflammatory bowel disease, such as Crohn’s disease or celiac disease, or if you have reduced pancreatic secretion of important digestive enzymes.
People who have had weight loss surgery can also be at risk for vitamin A deficiency. For many bariatric surgery patients, this deficiency can occur because you are eating a very low fat and low calorie diet. You may not be able to eat many fruits and vegetables for a while after surgery. Gastric bypass patients in particular may be at even higher risk for vitamin A deficiency since their surgery reduces fat and other nutrient absorption from food.
Signs of Vitamin A Deficiency
The first time you might notice a sign of vitamin A deficiency could be trouble seeing at night. Night blindness results because of vitamin A’s role in the visual cycle. When you do not have enough vitamin A, your eyes are not as sensitive to light and are not able to detect light as well when there is only a small amount present, which is the case at night. You can recover from night blindness, but it can progress to permanent total blindness if you do not treat it.
Other signs of vitamin A deficiency are related to its functions. Without enough vitamin A, you are more susceptible to infectious diseases because your immune system is not as strong. You might get sick more often. In addition, vitamin A deficiency along with low iodine status can make goiter even worse and cause poor thyroid function. You could feel cold, gain weight, and have an enlarged thyroid gland.
Since vitamin A is so closely related to skin health, it makes sense that vitamin A deficiency can cause symptoms in your skin. You could see lesions on your skin due to a condition called hyperkeratosis.
Why Use Vitamin A Supplements?
There are many reasons why you might want to consider taking vitamin A supplements. You should definitely consider them if you are not getting many good sources of vitamin A from the foods you eat. You should also consider vitamin A pills if you are in any of the high risk groups, such as bariatric surgery patients, individuals with celiac disease, or individuals with other fat malabsorption conditions.
You might also use vitamin A supplements if you believe they may provide extra benefits. For example, you might be interested in taking beta-carotene because you are interested in getting more antioxidants in your diet. Or, you might think that you are low on vitamin A and getting a little extra could improve your night vision. Just check with your doctor first.
Another reason why you might want to use vitamin A supplements is to support skin health. If you are especially concerned about exposure to the sun and the effects of photoaging, your doctor might be positive about trying topical creams. Just be aware that, according to Mayo Clinic, you may need to continue using creams to keep the effects coming.
Side Effects of Vitamin A Supplements
Vitamin A pills are generally safe in healthy individuals who take them in normal amounts. You can stay in a range near the RDA to keep your intake in check. It is also a good idea to check your vitamin A dosage with your healthcare provider to get a more personalized recommendation. Vitamin A side effects with topical creams can include signs such as redness of the skin, as well as itchiness.
Who Shouldn’t Take Vitamin A Supplements?
Most people can safely take vitamin A supplements in suggested doses, but nobody should take them without asking their doctor first. If you have liver disease, certain kinds of conditions that cause high cholesterol levels, or alcohol abuse, you should be especially wary of taking vitamin A pills.
Pregnant women and women who may become pregnant often need vitamin A supplements. However, too much can cause birth defects, too. So, the best course of action is to ask your doctor. You can get your diet evaluated and take a vitamin A blood test to find out if you should start taking vitamin A supplements.
Another group of people who should not take vitamin A supplements without a doctor’s approval are people who are at high risk for lung cancer. This might apply to you if, for example, you are a smoker or have chronic exposure to asbestos, which could apply if you work in construction or spend large periods of time in old buildings with exposed insulation with asbestos fibers. The following research study results explain why you should think twice about taking beta-carotene supplements.
Because of its antioxidant capacity, some researchers hoped that taking a beta-carotene supplement would help prevent lung cancer in high-risk patients. However, a famous research study had surprising results. As described in the journal “Current Medicinal Chemistry,” a study of 9,000 participants found that the individuals who took the high-dose vitamin A supplements – an amount of 7,500 RAE – actually had a higher risk for lung cancer than the control group who did not take these supplements.
How Much is Too Much Vitamin A?
The tolerable upper level of intake is the highest amount of a nutrient you can safely consume on average each day for a long period of time. For vitamin A, the upper level of intake is set at 3,000 RAE per day, which is about 3 to 4 times the RDA.
The chances of getting too much vitamin A are much lower if you are getting most of your vitamin A from vegetables and fruits with vitamin A. It is possible to get too much vitamin A from animal foods if you regularly eat the very best sources of vitamin A, such as beef liver, which, according to the Linus Pauling Institute, has over 6,000 RAE of preformed vitamin A in a single 2.5-ounce slice. That is about 7 or 8 times the amount you need in a day.
Vitamin A Toxicity Symptoms
When it comes to vitamins, toxicity can be acute, due to too much of the vitamin in a short period of time, or chronic, too much of the vitamin over months or years. Acute toxicity of vitamin A is not likely to happen from eating foods with vitamin A, but it can occur from dietary supplements.
Researchers at the University of Wisconsin at Madison describe some chronic and acute effects of vitamin A toxicity in the “American Journal of Clinical Nutrition.” Acute effects can include nausea, water retention, headaches, and decreased appetite, along with dry skin. You are not likely to get acute toxicity when you take regular vitamin A dosage amounts, but can you take too much vitamin A? Yes.
Chronic toxicity is unlikely to occur from foods, but it is possible when you take too many vitamin A pills without needing them. Some of the results of chronic toxicity include enlarged liver and spleen, weight loss, loss of appetite, and dry skin. Hemorrhage and coma can occur in very bad cases.
Too much vitamin A over time has also been linked to osteoporosis, or reduced bone mineral density and an increased risk of fractures. You can lower your risk not only by getting the proper dosage of vitamin A, but also by consuming plenty of calcium and vitamin D, exercising regularly, and avoiding smoking.
Carotenoids cannot cause these symptoms such as liver damage and osteoporosis. Only preformed vitamin A can lead to serious toxicity problems. With too much beta-carotene, you might experience an orange coloring of your skin. While you may not like the appearance, it is not distinctly dangerous to your health.
Always talk to your doctor before taking any sort of dietary supplement. Discuss any medications you are taking and health conditions you may have, and ask for a recommendation on which brand, form, and dose. You can lower your risk of toxicity and increase your chances of getting the benefits you had hoped for.
Vitamin A is an essential nutrient that can keep your eyes, skin, and immune system healthy. You can get it from your diet, but there may be times when you feel that a supplement can boost your levels. You are best off getting your vitamin A from a trusted provider and following the usage instructions carefully.
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Article reviewed by:
Absolvent of the Comenius University in Bratislava, Slovakia, Faculty of Pharmacy. Zuzana holds a PhD. in Pharmacognosy and Botany, during the course of which she worked on two projects studying medicinal plants, their active constituents and their effects on the human body. A trained pharmacist with 3 years experience and a first author of three publications, she is currently working on continuing her study of medicinal plants at University of Vienna, Austria.