Beta-carotene is a carotenoid, one of a group of plant pigments known to have antioxidant and other effects. This is a substance in plants that's quickly converted into vitamin A inside the body. Beta-carotene is often thought of as a form of vitamin A itself. Having normal levels of vitamin A is key for good vision, strong immunity, and general health.
Why do people take beta-carotene?

Beta-carotene has become popular in part because it's an antioxidant -- a substance that may protect cells from damage. A number of studies show that people who eat lots of fruits and vegetables that are rich in beta-carotene and other vitamins and minerals have a lower risk of some cancers and heart disease. However, so far studies have not found that beta-carotene supplements have the same health benefits as foods.

Beta-carotene supplements may help people with specific health problems. Supplements might be used in someone with a clear vitamin A deficiency. They also might help those with the genetic condition erythropoietic protoporphyria (EPP). Both conditions are rare.

There's some promising evidence that beta-carotene supplements might slow the course of osteoarthritis. Taking beta-carotene along with zinc and vitamins C and E may also help reduce progression of age-related macular degeneration, a leading cause of blindness in older people.

Beta-carotene supplements have been studied as a treatment for many other diseases. Examples include cataracts, Alzheimer's disease, and cystic fibrosis. The results have been inconclusive.
How much beta-carotene should you take?

While there is a recommended dietary allowance (RDA) for vitamin A, there is no RDA for beta-carotene specifically. Studies have used dosages ranging between 15 and 180 milligrams a day.

There is no set tolerable upper intake level (UL) for beta-carotene. However, high doses or long-term use may be dangerous.

Many experts recommend a combination of supplemental carotenoids (lutein, carotenes, zeaxanthine, lycopene, etc), rather than simply beta-carotene. The correct dose of mixed carotenoids for temporary or long-term use is unclear.
Can you get beta-carotene naturally from foods?

The American Heart Association suggests that you get beta-carotene (and other antioxidants) from food rather than supplements. Good food sources of beta-carotene include:

Carrots
Sweet potatoes
Winter squash
Spinach and kale
Fruits like cantaloupe and apricots

Beta-carotene levels are highest in fresh fruits and vegetables. Frozen and canned varieties generally have less.
What are the risks of taking beta-carotene?

Side effects. Taken at the amounts found in foods, beta-carotene has few side effects. At high levels, it may turn the skin yellowish or orange. This is temporary and harmless.
Risks. While their benefits are generally unclear, beta-carotene supplements do seem to have serious risks. People who smoke or who have been exposed to asbestos should not use beta-carotene supplements. Even low doses have been linked with an increased risk of cancer, heart disease, and death in these two groups of people. Excessive alcohol use combined with beta-carotene supplements may raise the risk of liver disease and cancer. In high doses, vitamin A, and presumably beta-carotene, can be toxic to the liver.
Interactions. If you take any regular medications, ask your doctor if beta-carotene supplements are safe. They may interact with cholesterol drugs and other medicines.