听力原文： The growing interest of consumers in the safety and more nutritional quality of the typical North American diet is a welcome development. However, much of this interest has been sparked by sweeping claims that the food supply is unsafe or inadequate in meeting nutritional needs. Although most of these claims are not supported by scientific evidence, such claims make it difficult for the general public to separate fact from fiction. As a result, claims that eating a diet consisting entirely of organically grown foods prevents or cures disease or provides other benefits to health have become widely publicized and form. the basis for folklore. Almost daily the public is besieged for 'no-aging' diets, new vitamins, and other wonderful foods. There are numerous unconfirmed reports that natural vitamins are superior to synthetic ones, that fertilized eggs are nutritionally superior to unfertilized eggs, that untreated grains are better than treated grains and the like. (1)