Professor of pediatrics Paul Offit reviews studies that cast doubt on the benefits of various dietary supplements. For example, individuals who take antioxidant supplements have been found to be less healthy:
How could this be? Given that free radicals [harmful atoms] clearly damage cells–and given that people who eat diets rich in substances that neutralize free radicals are healthier–why did studies of supplemental antioxidants show they were harmful? The most likely explanation is that free radicals aren’t as evil as advertised. Although it’s clear that free radicals can damage DNA and disrupt cell membranes, that’s not always a bad thing. People need free radicals to kill bacteria and eliminate new cancer cells. But when people take large doses of antioxidants, the balance between free radical production and destruction might tip too much in one direction, causing an unnatural state in which the immune system is less able to kill harmful invaders. Researchers have called this “the antioxidant paradox.”
Whatever the reason, the data are clear: high doses of vitamins and supplements increase the risk of heart disease and cancer; for this reason, not a single national or international organization responsible for the public’s health recommends them.