A、Protein was recognized as an essential component of diet. B、Vitamins were synthesized from foods. C、Effective measures of weig

Moderator:
    Good evening, ladies and gentleman. Today we are honored to have Professor Dreiser from the Johns Hopkins University. He will introduce to us the study of the relationship between health and nutrition-utilization. Professor Dreiser, please. Professor Dreiser:
    Thank you for your introduction, Cara. Well, the study of the relationship between health and how the body takes in and utilizes food substances can be divided into four distinct eras:
    The first era began in the nineteenth century and extended into the early twentieth century when it was recognized for the first time that food contained components that were essential for human function and that different foods provided different amounts of these essential agents. Near the end of this era, research studies demonstrated that rapid weight loss was associated with nutrition imbalance and could only be rectified by providing adequate dietary protein associated with certain foods.
    The second era was initiated in the early decades of the twentieth century and might be called the vitamin period. Vitamins came to be recognized in foods, and deficiency syndromes were described. As vitamins became recognized as essential food constituents necessary for health, it became tempting to suggest that every disease and condition for which there had been no previous effective treatment might be responsive to vitamin therapy. At that point in time, medical schools started to become more interested in having their curricula integrate nutritional concepts into the basic sciences. Much of the focus of this education was on the recognition of vitamin deficiency symptoms. Herein lay the beginning of what ultimately turned from ignorance to denial of the value of nutritional therapies in medicine. Reckless claims were made for effects of vitamins that went far beyond what could actually be achieved from the use of them.
    In the third era of nutritional history in the early 1950s to mid-1960s, vitamin therapy began to fall into disrepute. Together with this, nutrition education in medical schools also became less popular. It was just a decade before this that many drug companies had found their vitamin sales skyrocketing and were quick to supply practicing physicians with generous samples of vitamins. Expectations as to the success of vitamins in disease control were exaggerated. As is known in retrospect, vitamin and mineral therapies are much less effective when applied to health-crisis conditions than when applied to long-term problems of undernutrition that lead to chronic health problems.
    And the fourth era…
    16.According to Professor Dreiser, which of the following discoveries was made during the first era in the history of nutrition?
    17.What is the purpose of teaching concepts of nutrition in medical schools?
    18.Why did vitamin therapy become less popular in the 1950s?