Nutritionists agree that eating foods high in fiber, vitamins and minerals and low in fat is important. But experts disagree on certain key questions. Some scientists say high doses of certain vitamins help prevent cancer and other serious ailments. Others argue that supplements are ineffective and can't substitute for a balanced diet. Cutting back on red meat significantly reduces the risk of many chronic illnesses, but some scientists argue that moderate meat consumption is actually healthy. Experts also differ on alcohol. A growing body of research indicates a drink or two a day reduces the risk of heart disease and stroke, but many health experts say that the benefits of alcohol are far outweighed by the damage done by immoderate drinking.

David Masci specializes in social policy, religion and foreign affairs. Before joining CQ Researcher as a staff writer in 1996, he was a reporter at CQ's Daily Monitor and CQ Weekly. He holds a BA in medieval history from Syracuse University and a law degree from The George Washington University.