A yellow-orange member of the family of plant pigments called carotenoids, beta-carotene is an antioxidant nutrient that the body converts into vitamin A. Of the more than 600 carotenoids that have been identified, beta-carotene has the greatest pro-vitamin A activity and has been the most extensively researched. Other notable members of the carotenoid family include lycopene, alpha carotene, lutein, zeaxanthin, capsanthin, and cryptoxanthin. While most of these carotenoids are not significant sources of vitamin A, they may still play a useful role as dietary antioxidants. Although most beta-carotene research has focused on pro-vitamin A activity, the nutrient appears to provide significant health benefits beyond its role as a vitamin A precursor.
The most common supplemental beta-carotene intake is 25,000 IU (15 mg) per day, although many studies have used twice that amount with no adverse effects. Many nutritional researchers consider beta-carotene to be the safest source of supplemental vitamin A because high doses of vitamin A can lead to toxic accumulations in the liver, whereas beta-carotene is only converted into vitamin A as needed and does not cause toxic build-up. Excessive beta-carotene intake can cause yellowing of the skin, a harmless effect that passes when intake is reduced. Nutritionists often recommend combining beta-carotene with other antioxidants such as vitamins C and E, selenium, and zinc.