Call it the beta-carotene quandary. Researchers are scrambling to figure out why foods rich in beta-carotene seem to reduce the risk of lung cancer while high doses of beta-carotene supplements seem to increase the risk.
One theory--that massive doses of beta-carotene keep people from absorbing other substances in fruits and vegetables that may be the real protectors--now has new support from a study from the National Cancer Institute in Bethesda, Maryland.