Human clinical nutrition studies, when feasible, are among the best research approaches for addressing the links between diet and atherosclerosis. Moreover, because of their great relevance to everyday life, their findings are quickly publicized. Often, however, such studies do not yield consistent or reproducible results. The resulting transmission of mixed messages to the scientific and lay communities seriously undermines both the credibility of nutrition research and the public's confidence in the possibility of obtaining reliable and practical advice on how to modify diet. Oat bran, with its rise and fall in the scientific and popular press as well as in the marketplace, is a good example of this phenomenon.