From antiquity, vegetarian diets have been followed for a variety of reasons, albeit with widely differing nutritional outcomes. As a result, numerous scientific and professional questions have arisen. Currently, professional interest in vegetarian nutrition has reached unprecedented levels. This is only partly explained by the growing number of vegetarians nd the increased popularity of vegetarian diets.
As disease patterns shifted away from nutrient deficiencies and toward diet-related chronic diseases, vegetarian nutrition research also changed emphasis, and the benefits of vegetarian diets have begun to emerge.

In the past 30 years, scientific endeavors in the area of vegetarian nutrition seem to have progressively shifted from investigating concerns held by nutritionists and other health professionals to a fertile area of investigation in which creative solutions for various medical conditions and preventive approaches to chronic diseases may be found.
Despite this broadening shift in the focus and study of nutrition, current knowledge regarding the relationship between vegetarian diets and human health is far from complete. However, scientific advances made during the last few decades have noticeably changed the role of vegetarian diets and other diets largely based on plant foods in human nutrition and public health.

From antiquity, the phenomenon of speech has been an object of both general curiosity and scientific inquiry. Over the centuries, much effort has been devoted to the study of this remarkable process whereby our eating and breathing apparatus is used to transform thoughts in the mind of a speaker into vibrations in the air and back into congruent thoughts in the mind of a listener. Although we still do not have satisfactory answers to many of the questions about speech and language that the ancients pondered, we do have substantial scientific knowledge of the subject and an evolving technology based on it.