UNIT X SECTION 3 VITAMINS, ENZYMES, AND HORMONES CATALYZE THE CHEMICAL REACTIONS IN LIVING ORGANISMS The group of physiological catalysts consisting of vitamins, enzymes, and hormones has been the object of a tremendous amount of research during the past quarter of a century. When one realizes that these substances are present in living organisms in extremely minute quantities, one can appreciate the magnitude of the achievement which is represented by the separation, purification, analysis, and synthesis of so many of these catalysts. Little is known concerning many of these substances beyond the recognition of their existence. Few fields of research have been so fruitful in their benefits to the health of mankind, and few fields of research have been so dependent upon the methods of both the physical and biological sciences. The main purpose of this Section is to tell enough about what has been done in the study of physiological catalysts to cause you to be alert to the developments during the next quarter of a century, which may give man an unbelievable control over the growth, development, and nature of living organisms. Vitamins Are Physiological Catalysts Synthesized by Plants. The term vitamin refers to a group of substances present in very minute concentrations in many foods which are essential to normal nutrition. One of the earliest observations concerning vitamins was that beriberi, a disease characterized by paralysis of the legs, general weakness, dropsy, and anemia is common among people whose main article of food is polished rice. Beriberi threatened the fighting efficiency of the Japanese army in the Russo-Japanese War in 1905. The troops were being fed large quantities of polished rice. Someone remembered the work of a Dutch scientist, Eijkman, who in 1897 artificially produced beriberi in pigeons by feeding them polished rice and then cured them 738
VITAMINS, ENZYMES, AND HORMONES 739 by feeding them rice polishings. Shortly after the Japanese Army substituted brown rice for polished rice, beriberi disappeared. Vitamin Research Has Followed a Well-established Pattern. 1. The proof that an abnormal or diseased condition results from vitamin-deficient foods. 2. The preparation of vitamin concentrates such as rice-hull extract from foods which are known to contain the vitamins in question. 3. The separation of pure vitamins from concentrates. 4. The analysis of these pure vitamins to determine their empirical and structural formulas. 5. The synthesis of the vitamins in relatively large quantities. 6. The determination of the proper daily requirements of these synthetic vitamins for optimum health. Many Different Vitamins Have Been Discovered. In the early stages of vitamin research, the vitamins were designated by letters of the alphabet because their chemical composition was unknown. These vitamins were classified according to their solubility in fats and water as follows: Fat-soluble Vitamins. A, D, and E. Water-soluble Vitamins. B, C, and G. A very large amount of research resulting in the isolation, analysis, and synthesis of a number of the vitamins has resulted in these vitamins gradually coming to be known under their chemical names. This research has also shown that what was formerly known as vitamin B, for example, is really a mixture of a number of water-soluble vitamins. " vitamin-B Complex," refers to all the vitamins present in extracts of yeast, rice polishings, etc. nicotinic acid, postulated factors. This complex includes thiamin, riboflavin, pantothenic acid, pyridoxine, and at least seven other It is generally agreed by experts that if half the caloric value of the diet were derived from milk, eggs, meat, and meat products, fruits and vegetables, and if half of whatever cereal products are eaten consist of whole grain products, and furthermore, if there is sufficient exposure to sunshine to meet the vitamin D requirements, there will be no danger of vitamin or any other type of nutritive deficiency.^ The following chart summarizes, the most important information available in 1941 concerning the sources and functions of the vitamins. 'Supplement to the American Journal of Public Health, American Public Health Association Year Book, 1937-1938. February, 1938, p. 79.