Vitamin A is an essential nutrient that your body doesn't make. You have to get it through foods or supplements.
There are two main types of vitamin A:
Preformed vitamin A: It comes from animal products such as liver, eggs, fish, and dairy. Preformed vitamin A is already in a form that your body can digest and absorb.
Provitamin A: Provitamin A comes from plant sources such as carrots, tomatoes, cantaloupes, sweet potatoes, and leafy greens. Your body converts it into usable forms of vitamin A.
Both types of vitamin A are available in supplement form, but research suggests that your body can best absorb it through foods. Eating foods rich in vitamin A is important for maintaining your reproductive health, eyesight, and immune system.
The American Heart Association recommends getting antioxidants, including beta-carotene, by eating a well-balanced diet high in fruits, vegetables, and whole grains rather than from supplements until more is known about the risks and benefits of supplementation.
High doses of vitamin A may do more harm than good. Some research shows that taking vitamin A could increase your risk of certain cancers, heart disease, and early death.
Why You Need Vitamin A
Vitamin A plays an important role in many areas of your health:
Eye health: Getting enough vitamin A helps maintain the health of the retinas of your eyes and prevent age-related macular degeneration.
Immune health: Your immune system is a complex collection of different cells that keep you healthy. Vitamin A plays an important role in helping these cells communicate and fight germs and infections.
Reproductive health: Vitamin A helps prevent birth defects and reduces the risk of infertility.
Skin health: Low vitamin A can cause problems such as dry, scaly, and itchy skin.
Healthy growth: Kids who don't get enough vitamin A might not grow and develop normally.
Why Do People Take Vitamin A Supplements?
Adults need between 700 and 900 micrograms (mcg) of vitamin A every day to avoid a deficiency. Most people can get that through food, but some people with certain health conditions may need supplements to help them meet their needs. This includes people with cystic fibrosis, a condition that damages the digestive tract and makes it harder to absorb vitamins through food. People with digestive disorders such as celiac disease and Chron's disease may also need vitamin A supplements.
People also use vitamin A as a treatment for acne , but research still hasn't proven its effectiveness. Research shows that a vitamin A supplement can help people with age-related macular degeneration, a condition that causes older people to lose their vision. Oral vitamin A is also used as a treatment for measles and dry eye in people with low levels of vitamin A.
Vitamin A Deficiency
Vitamin A deficiency is rare in the U.S. Most people get enough vitamin A from their diets. If you have a vitamin A deficiency, you might notice you have bad night vision. This is called xerophthalmia, and it's the most common symptom of not having enough vitamin A.
If your levels of vitamin A are low for a long time, you have a higher risk of diseases that affect the lungs, such as pneumonia, and infections such as diarrhea and measles. Anemia is another risk you face. Anemia happens when your blood cells aren't working well, and they can't deliver enough oxygen throughout your body.
Sources of vitamin A
If you don't have a health condition that requires supplements, it is ideal to get all your vitamin A through food. The health benefits of vitamin A from food sources are well established, but the benefits from synthetic supplements are not as clear.
Good dietary sources of vitamin A or beta-carotene include:
- Beef liver and other organ meats
- Fish, especially herring and salmon
- Leafy greens
- Sweet potato
- Fortified breakfast cereals
Vitamin A Foods
Many foods are rich in vitamin A, so it’s generally easy to get your daily requirement of this vitamin from your diet. These six foods are some of the best sources of dietary vitamin A available.
Liver. It is the richest source of vitamin A outside of supplements. A 4-ounce serving of beef liver contains as much as 5,620 mcg of vitamin A. That's almost double the daily upper limit for adults. Because of that and liver's high level of cholesterol, you shouldn't eat it more than once a week to avoid consuming too much of the vitamin.
Dairy. Dairy is a good source of vitamin A on its own. In the U.S., many types of dairy milk are also fortified with the vitamin, which means they have supplemental vitamin A added during manufacturing. One cup of 2% milk with added vitamin A has 137 mcg of the vitamin. One slice of sharp cheddar cheese has 74 mcg.
Sweet potato. A medium sweet potato contains an impressive 1,190 mcg of vitamin A. That’s more than 150% of your daily requirement in a single serving.
Spinach. One cup of raw spinach contains 141 mcg of vitamin A.
Carrots. One large carrot has 601 mcg of vitamin A.
Cantaloupe. One large slice of cantaloupe has 172 mcg of vitamin A.
Vitamin A Benefits
Vitamin A is essential for your overall health. Most people get enough vitamin A from their diet, but people with certain medical conditions can benefit from additional vitamin A supplements.
Vitamin deficiency. Vitamin A deficiency is uncommon in developed countries, where most people get enough vitamin A from their diet. A deficiency in vitamin A can cause fatigue, eye dryness, infertility, and blindness.
Measles. Measles increases the chances of vitamin A deficiency. Giving vitamin A to children with measles reduces their risk of death.
Cystic fibrosis. Problems with the digestive system that occur with cystic fibrosis increase the risk of vitamin A deficiency.
Macular degeneration. A vitamin mix including beta-carotene slows vision loss in people with macular degeneration.
Infectious diseases. Vitamin A can be used in the treatment of several infectious diseases. It has anti-inflammatory properties and can boost your immune system.
- Cancer. While there is some evidence suggesting that vitamin A might help some cancers, research shows it can also increase the risk of other cancers.
How Much Vitamin A Should You Take?
The recommended dietary allowance (RDA) includes the vitamin A you get from both the food you eat and any supplements you take.
Vitamin A: Recommended Dietary Allowance (RDA) in Micrograms (mcg) of Retinol Activity Equivalents (RAE)
14 years and up
14-18 years: 750 mcg/day
Under 19 years: 1,200 mcg/day
19 years and over: 1,300 mcg/day
14 years and up
The tolerable upper intake levels of a supplement are the highest amount that most people can take safely. Higher doses might be used to treat vitamin A deficiencies. But you should never take more unless a doctor says so.
Tolerable Upper Intake Levels (UL) of Retinol* in Micrograms (mcg) of Retinol Activity Equivalents (RAE)
19 years and up
* There is no upper limit for vitamin A from beta-carotene.
Vitamin A Risks
Taking too much vitamin A can cause negative, possibly life-threatening, side effects.
If you decide to take a vitamin A supplement, always ask your doctor first if it's a good idea. Getting too much preformed vitamin A from supplements and animal-based foods can be harmful. It can cause:
If you're pregnant, taking too much vitamin A could cause birth defects, such as abnormalities of the eyes, heart, lungs, or skull. You also should avoid high doses of vitamin A if you are breastfeeding.
There is an upper limit (UL) set for vitamin A. Adults shouldn't get more than 3,000 mcg per day of preformed vitamin A. Some supplements may have far more than this.
Getting too much beta-carotene, or provitamin A, from plant sources doesn't cause any serious problems. But you should know that too much of it can cause your skin to turn yellowy-orange. This is called carotenemia. It's not permanent, and when you lower your intake it will go away.
Vitamin A supplements can also interact with some medications, such as:
Orlistat (Alli, Xenical)
Vitamin A toxicity
Hypervitaminosis A, or vitamin A toxicity, can happen after taking a single large dose of vitamin A or taking smaller doses over a longer period. Symptoms include:
- Feeling sleepy
- Liver damage
- Peeling, oily, cracked, and itchy skin that is more sensitive to sunlight
- Dry eyes
- Hair loss or oily hair
- Blurry vision
- Low appetite
- Bone pain
Severe hypervitaminosis A can lead to coma and death. Vitamin A toxicity is an even bigger risk for babies and children. They can have vitamin A poisoning from even smaller doses of the nutrient.