Vitamin A

Definition

Vitamin A is a fat-soluble vitamin that is stored in the liver.

There are two types of vitamin A that are found in the diet.

Vitamin A is also available in dietary supplements. It most often comes in the form of retinyl acetate or retinyl palmitate (preformed vitamin A), beta-carotene (provitamin A) or a combination of preformed and provitamin A.

Function

Vitamin A helps form and maintain healthy teeth, skeletal and soft tissue, mucus membranes, and skin. It is also known as retinol because it produces the pigments in the retina of the eye.

Vitamin A promotes good eyesight, especially in low light. It also has a role in healthy pregnancy and breastfeeding.

Vitamin A is found in two forms:

Beta-carotene is an antioxidant. Antioxidants protect cells from damage caused by substances called free radicals.

Free radicals are believed to:

Eating food sources of beta-carotene may reduce the risk for cancer.

Beta-carotene supplements do not seem to reduce cancer risk.

Food Sources

Vitamin A comes from animal sources, such as eggs, meat, fortified milk, cheese, cream, liver, kidney, cod, and halibut fish oil.

However, many of these sources, except for Vitamin A fortified skim milk, are high in saturated fat and cholesterol.

The best sources of vitamin A are:

The more deep the color of a fruit or vegetable, the higher the amount of beta-carotene. Vegetable sources of beta-carotene are fat- and cholesterol-free. Their absorption is improved if these sources are eaten with a fat.

Side Effects

DEFICIENCY:

If you do not get enough vitamin A, you have more risk of eye problems such as:

Lack of vitamin A can lead to hyperkeratosis or dry, scaly skin.

HIGH INTAKE:

If you get too much vitamin A, you can become sick.

Babies and children are more sensitive to vitamin A. They can become sick after taking smaller doses of vitamin A or vitamin A-containing products such as retinol (found in skin creams).

Large amounts of beta-carotene will not make you sick. However, high amounts of beta-carotene can turn the skin yellow or orange. The skin color will return to normal once you reduce your intake of beta-carotene.

Recommendations

The best way to get the daily requirement of important vitamins is to eat a wide variety of fruits, vegetables, fortified dairy foods, legumes (dried beans), lentils, and whole grains.

The Food and Nutrition Board of the Institute of Medicine -- Dietary Reference Intakes (DRIs) Recommended Intakes for individuals of vitamin A:

Infants (average intake)

The Recommended Dietary Allowance (RDA) for vitamins is how much of each vitamin most people should get each day. The RDA for vitamins may be used as goals for each person.

Children (RDA)

Adolescents and adults (RDA)

How much of each vitamin you need depends on your age and gender. Other factors, such as pregnancy and your health, are also important. Ask your health care provider what dose is best for you.


Review Date: 2/2/2019
Reviewed By: Emily Wax, RD, CNSC, University of Virginia Health System, Charlottesville, VA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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