In one experiment, Harvard researchers assigned 22,000 doctors to take either 50 mg of beta carotene (more than twice the amount typically found in a multivitamin) or a placebo every other day for 12 years. In a second trial. 18,000 people with histories of smoking or asbestos exposure took beta carotene and other vitamin-A supplements in hope of warding off lung cancer. Neither study showed any benefit, federal health officials announced last week. In the second study, in fact, the supplement takers suffered slightly more than their share of cancer, prompting the researchers to halt the experiment early.
None of this means that diet doesn’t matter. People who entered the studies with the highest blood levels of beta carotene were the least likely to develop lung tumors, presumably because foods rich in that nutrient contain countless others. The lesson, says Dr. Charles Hennekens, director of the Harvard study, is that popping a pill “can neither substitute for a good diet nor compensate for a bad one.”
