Vitamin A
Vitamin A is a nutrient that is important for vision growth, cell division, reproduction, and immunity. It also has antioxidant properties. These properties might protect your cells from the effects of free radicals, which are molecules produced when your body does not use oxygen properly. A free radical is a molecule that breaks down food or is exposed to tobacco smoke and radiation. This might contribute to heart disease, cancer, and other illnesses.
Vitamin A is found in many foods, including spinach, dairy products, and liver. Other sources of vitamin A include foods that are high in beta-carotene, such as leafy green vegetables, carrots, and cantaloupe. The body converts beta-carotene into vitamin A.
Vitamin A is most beneficial when taken as an oral supplement by people who have a poor diet or who have a condition that increases the need for this vitamin, such as pancreatic disease, eye disease, or measles. Remember that taking a supplement might not provide the same level of antioxidant protection as eating foods containing this nutrient. The antioxidants in these supplements offer the same benefits as those found naturally in food.
The recommended daily amount of vitamin A is the equivalent of 900 micrograms (mcg) for adult men and 700 mcg for adult women.
Evidence
Some research on oral vitamin A for specific conditions shows that:
- Acne.Large doses of oral vitamin A supplements do not appear to have an acne-inducing effect.
- Age-related macular degeneration.A large clinical trial found that people at high risk of advanced age-related macular degeneration reduced their risk of developing the condition by 25 percent by taking a specific combination of vitamins. It's not clear which role beta-carotene played.
- Cancer.There is still much unknown about how using vitamin A supplements can reduce the risk of various types of cancer.
- Measles.Children who are at an increased risk of vitamin A deficiency should take a vitamin A supplement. Research suggests that taking a vitamin A supplement might reduce the number of deaths due to measles.
- Vitamin A deficiency.People who have low levels of vitamin A seem to benefit the most from taking supplements. This deficiency is not common in the United States. Vitamin A deficiency can cause anemia and dry eyes.
Vitamin A is used to reduce wrinkles, splotches, and roughness on the skin; it is also used to treat acne.
Our take
Caution
A healthy diet will provide most people with enough vitamin A. If you're interested in the antioxidant properties of food sources, natural antioxidants are best. Too much vitamin A can be harmful, however, so it's important to be aware of the benefits and limits of vitamin A foods. Taking in too much vitamin A during pregnancy can be harmful and lead to birth defects.
Safety and side effects
Too much vitamin A can be harmful. Too much even a small amount of vitamin A (over 200,000 mcg) can cause:
- Nausea
- Vomiting
- Vertigo
- Blurry vision
Oral vitamin A supplements taken over a long period of time can be harmful. Taking more than 10000 mcg per day can be harmful.
- Bone thinning
- Liver damage
- Headache
- Diarrhea
- Nausea
- Skin irritation
- Pain in the joints and bone
- Birth defects
Before taking vitamin A, talk to your doctor if you are pregnant. Taking too much of this vitamin during pregnancy has been linked to birth defects.
Interactions
Possible interactions include:
- Anticoagulants.Taking vitamin A supplements while taking these medications used to prevent blood clots might increase your risk of bleeding.
- Bexarotene (Targretin).Taking a vitamin A supplement while using this cancer drug increases the risk of side effects such as itchy, dry skin.
- Hepatotoxic drugs.Taking high doses of vitamin A supplements can lead to liver damage. If you are also taking drugs that can damage the liver, your risk of liver disease will increase.
- Orlistat (Alli, Xenical).This weight-loss drug can decrease the absorption of food sources of vitamin A. So your doctor might suggest you take a multivitamin that includes vitamin A and beta-carotene while taking this medication.
- Retinoids.Do not take vitamin A supplements and prescription drugs at the same time. This could increase the risk of high blood levels of vitamin A.