1. Clinical trials have limitations beyond their exorbitant costs and the years or decades it takes them to provide meaningful results. A. Randomly subjecting thousands of individuals to second-hand tobacco smoke, pollutants or potentially noxious trans fats presents obvious ethical dilemmas. B. Clinical trials invariably enroll subjects who are relatively healthy, who are motivated to volunteer and will show up regularly for treatments and checkups. C. They can rarely be used, for instance, to study suspected harmful effects. D. And even when these trials are done to study the benefits of a particular intervention, it's rarely clear how the results apply to the public at large or to any specific patient. 6. Randomized trials are very good for showing that a drug does what the pharmaceutical company says it does but not very good for telling you how big the benefit really is and whatare the harms in typical people.