Beta-carotene is the most active of the deeply colored pigments called carotenoids. After consumption, beta-carotene converts to retinol, a readily usable form of vitamin A. Beta-carotene's beneficial effects include protecting the skin from sunlight damage, fighting early cancer cells, boosting immunity, and preventing cataract formation. It also stops the creation of free radicals (oxidants), which are DNA-damaging molecular fragments in the body.
Food sources of beta-carotene include carrots, spinach, kale, and broccoli, as well as animal sources such as liver, whole eggs, and whole milk. Since beta-carotene is fat-soluble, most fat-free milk has been fortified with vitamin A to replace what is lost when the fat is removed.
Vitamin A is stored in the body, and an excess amount can lead to acute symptoms, such as vomiting and muscle weakness, as well as chronic problems such as liver abnormalities, birth defects, and osteoporosis. In addition, beta-carotene supplements have been found in some studies to actually increase the risk of cancer in smokers. (Excess beta-carotene is not stored in the body, however.) Because of these dangers, the Institute of Medicine recommends that beta-carotene supplements are not to be used by the general public. The institute does advocate the use of such supplements for populations with inadequate vitamin A intake.
Margen, Sheldon, and the Editors of UC Berkeley Wellness Letter (2002). Wellness Foods A to Z: An Indispensable Guide for Health-Conscious Food Lovers. New York: Rebus.
National Institutes of Health (NIH) Clinical Center. "Vitamin A and Carotenoids." Available from <http://www.cc.nih.gov>
Wellness Guide to Dietary Supplements. "Beta-Carotene." Available from <http://www.berkeleywellness.com>