Vitamin A

Overview

Vitamin A is a nutrient the body uses to support growth, vision and cell function. It's also called retinol or retinoic acid. Vitamin A has antioxidant properties. Antioxidants are substances that might protect cells against the effects of free radicals. Free radicals are molecules made from reactions in the body or when the body is exposed to tobacco smoke or radiation. Free radicals might play a role in heart disease, cancer and other conditions.

Vitamin A is found in many foods, such as spinach, eggs, dairy products, and yellow and orange vegetables. Vitamin A also is added to some foods, such as milk, margarine and cereals. Colorful fruits and vegetables, such as carrots and cantaloupe, are high in beta-carotene. The body changes beta-carotene into vitamin A.

Taking too many vitamin A supplements can be harmful. Most people who eat a variety of food don't need to take vitamin A supplements. Those who don't have a lot of access to a variety of fresh foods or food from animals, such as people living in lower income countries, may take vitamin A supplements. People with some conditions, such as cystic fibrosis, or people who are pregnant may not get enough vitamin A, also called vitamin A deficiency. They may need to take vitamin A supplements. People with conditions that keep them from absorbing nutrients, such as Crohn's or celiac disease, also may need to take vitamin A supplements.

If you take vitamin A for its antioxidant properties, keep in mind that the supplement might not offer the same benefits as vitamins found naturally in foods.

The recommended daily amount of vitamin A is 900 micrograms (mcg) for men and 700 mcg for women. Daily vitamin A needs change slightly to 770 mcg for pregnant people and 1,300 micrograms for people who are breastfeeding.

What the research says

Research on vitamin A taken by mouth, also called oral vitamin A, for specific conditions shows:

• Acne. Large doses of oral vitamin A supplements don't seem to affect acne.
• Age-related macular degeneration. A large clinical trial showed that people at high risk of advanced age-related macular degeneration lowered their risk of developing the condition by taking a specific combination of vitamins that included beta-carotene. It's not clear what role beta-carotene played.
• Cancer. Some research studies suggest that people who eat a diet high in vitamin A may lower their risk of cancers of the pancreas, ovaries and food pipe, also called the esophagus. The connection between use of vitamin A supplements and lowered risk of cancers of the liver, colon, rectum and prostate and other types of cancer isn't clear.
• Heart disease. Vitamin A is an antioxidant, but research hasn't shown that taking vitamin A supplements helps prevent heart disease.
• Measles. Children with low vitamin A levels who get measles are more likely to be very sick than are children with recommended levels. Vitamin A supplements do not prevent measles. Getting a measles vaccine is the most effective and safest way to prevent measles. Don’t give vitamin A to children as a treatment or supplement unless a healthcare professional recommends it. Only take the recommended amount. Taking too much vitamin A can cause major harm.
• Vitamin A deficiency. People who have low levels of vitamin A, called vitamin A deficiency, seem to benefit most from vitamin A supplements. This kind of deficiency is rare in the United States. Vitamin A deficiency causes anemia and dry eyes.

Beyond use as a supplement taken by mouth, vitamin A is used in creams put on the skin to lessen fine wrinkles, splotches and roughness and treat acne.

Our take

Caution

A healthy diet with colorful fruits and vegetables gives most people enough vitamin A. If you're interested in the antioxidant properties of vitamin A, food sources are best. It's not clear whether vitamin A supplements offer the same benefits as antioxidants that are naturally found in food. Too much vitamin A can be harmful and too much vitamin A during pregnancy has been linked to birth defects.

Safety and side effects

Too much vitamin A can be harmful. Taking a single large dose of 200,000 mcg or many large doses can cause:

• Nausea.
• Vomiting.
• Fatigue.
• Dizziness.
• Blurry vision.

Taking more than 10,000 mcg a day of oral vitamin A supplements long-term can cause:

• Balance issues.
• Liver damage.
• Headache.
• Nausea.
• Hair loss.
• Dry skin.
• Pain in the joints and bones.
• Rarely, death.

If you are or might become pregnant, talk with your healthcare professional before taking vitamin A. The use of too many vitamin A supplements during pregnancy has been linked to birth defects. So has applying vitamin A creams to the skin. Examples include the creams isotretinoin and etretinate.

Interactions

Possible interactions include:

• Hepatotoxic medicines. Taking high doses of vitamin A supplements can cause liver damage. Combining high doses of vitamin A supplements with other medicines that can damage the liver, called hepatoxic medicines, could raise the risk of liver conditions.
• Orlistat (Alli, Xenical). This weight-loss medicine can lower how well the body absorbs food sources of vitamin A. Your healthcare professional might suggest that you take a multivitamin with vitamin A and beta-carotene while taking this medicine.
• Retinoids. Don't use vitamin A supplements and these prescription medicines that are taken by mouth at the same time. This could raise the risk of high levels of vitamin A in the blood.
• Warfarin (Jantoven). Use of vitamin A supplements while taking this medicine used to prevent blood clots might raise your risk of bleeding.