Vitamin a: medlineplus medical encyclopedia

Medically reviewed by Jennie Olopaade, PharmD, RPH — Written by Megan Ware, RDN, L.D. — Updated on January 4, 2021

Vitamin A is an essential vitamin that the body toàn thân needs for growth & development. It is also vital for cell recognition, vision, immune function, & reproduction.

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It also helps the heart, lungs, kidneys, & other organs function correctly.

Vitamin A deficiency is rare in the United States. If it happens, it can lead to lớn eye problems, including night blindness.

In this article, learn more about the types of vi-ta-min A, what vi-ta-min A does, và some good sources of it.


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Vitamin A occurs in different forms. The danh mục below will provide more detail.

Preformed vi-ta-min A occurs in meat, fish, and dairy produce.Provitamin A is present in fruits, vegetables, and other plant-based products.Retinol is the main active size of vi-ta-min A in the blood. Retinyl palmitate is the storage form of the vitamin.

Beta-carotene is, in itself, an antioxidant, but the toàn thân can also convert it into vi-ta-min A as needed.


Vitamin A contributes to various bodily functions & helps prevent a range of problems, including:

fertility issuesdelayed growth in children

Consuming an adequate amount of vitamin A may have the following benefits.

Lower cancer risk

Some experts have looked at whether or not adequate intakes of carotenoids can help reduce the risk of lung, prostate, và other types of cancer.

However, research has produced mixed results.

Healthful skin & hair

Vitamin A is important in the growth of all bodily tissues, including skin và hair.

It contributes to lớn the production of sebum, which is the oil that helps maintain levels of moisture in the skin and hair.

Learn more about how to lớn use vi-ta-min A for acne here.


For more in-depth resources about vitamins, minerals, và supplements, visit our dedicated hub.


Food sources

The form of vitamin A will depend on the source.

For example, ready-made retinol — which is the active khung of vi-ta-min A — only comes from animal sources.

The richest sources of retinol include:

organ meats, such as liverfatty fish, such as tuna và herringmilk and cheeseeggs

Plant-based foods contain carotenoids, which are antioxidant forms of vi-ta-min A. The toàn thân converts these into retinol as it needs.

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Carotenoid is an orange pigment that contributes to the màu sắc of certain fruits và vegetables.

Fruit & vegetable sources that are rich in carotenoids are often orange. They include:

squashred peppers

Plant foods that are rich in beta-carotene include dark green leafy vegetables, such as:

Learn more about food sources of vitamin A here.


Recommended intake

The recommended intake of vi-ta-min A varies according to age. People also need more during pregnancy and while breastfeeding.

It is available in several forms, and the vi-ta-min A content in foods is often measured as retinol activity equivalents (RAEs).

One RAE is equal to:

1 microgram (mcg) of retinol12 mcg of beta-carotene from food2 mcg of beta-carotene from supplements3.33 international units of vi-ta-min A

The recommended daily allowances of vitamin A by age are as follows:

up khổng lồ 6 months: 400 mcg7–12 months: 500 mcg1–3 years: 300 mcg4–8 years: 400 mcg9–13 years: 600 mcg14+ years: 900 mcg for males & 700 mcg for females

During pregnancy, the requirement is 770 mcg per day. While breastfeeding, it is 1,300 mcg per day.

The 2007–2008 National Health & Nutrition Examination Survey found that the average U.S. Individual, aged 2 years & above, consumes 607 mcg of vitamin A per day.

Who is at risk of deficiency?

Those at highest risk of deficiency include:

preterm infantsinfants và children in developing countriespregnant & lactating people in developing countries

People who use the weight loss drug orlistat may have a higher risk of deficiency. Orlistat reduces the body’s ability lớn absorb fat soluble vitamins such as vi-ta-min A.

Vitamin A supplements are available for those whose bodies have difficulty absorbing the nutrient, but it is best lớn meet needs through food, where possible.

This is because the use of supplements can mask possible deficiencies of other nutrients. This may lead lớn further health issues.


Preformed vitamin A can be toxic when people consume too much, either through their diet or through supplementation.

The tolerable upper intake cấp độ for vitamin A varies by age. The upper intake level is the amount above which vi-ta-min A intake may be toxic.

The các mục below details the upper intake levels for preformed vi-ta-min A by age:

up lớn 3 years: 600 mcg per day4–8 years: 900 mcg per day9–13 years: 1,700 mcg per day14–18 years: 2,800 mcg per day19+ years: 3,000 mcg per day

It does not appear that a person can consume too much beta-carotene, as the body will only convert it into vi-ta-min A as necessary.

Vitamin A toxicity

That said, consuming too much preformed vi-ta-min A can lead lớn vitamin A toxicity, or hypervitaminosis A.

Symptoms can include:

changes in skin colorpeeling on the palms of the hands and soles of the feetcracked skin on the fingersallergic tương tác dermatitisectropion, which affects the skins around the eyes dry lips, mouth, and nose, which can increase the risk of infectionreduced sebum production

Long-term overuse can lead to:

changes in bone formationliver damage

During pregnancy, consuming too much retinol can increase the risk of an infant being born with:

heart problems

The use of the topical treatment retinol may also increase vi-ta-min A levels to lớn an unhealthy level. People tend khổng lồ use retinol as an anti-aging skin cream.

Topical products can have adverse effects on the skin, though these will likely be less severe than those resulting from oral overconsumption. However, people should avoid using them during pregnancy.

The highest risk of overconsumption is with supplements. A healthful, balanced diet is unlikely khổng lồ lead lớn toxic levels of vi-ta-min A. It should also provide enough vitamin A without needing supplements.

Isotretinoin

Another possible cause of vi-ta-min A toxicity is the use of retinol-based medications. Isotretinoin (Accutane) is one such example. Doctors sometimes prescribe isotretinoin for severe acne.

Anyone using this treatment should avoid taking vi-ta-min A supplements because this drug is a vi-ta-min A derivative.

A doctor will not prescribe isotretinoin if a person is pregnant or may become pregnant.

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