Vitamins of the B Complex
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Vitamins of the B Complex GRACE A. GOLDSMITH iiN investigation of beriberi in the when he fed them natural rice. Birds Z\ late 19th century started the fed whole rice remained well. X A., chain of events that led to He noted that the disease that the discovery of vitamins. Beriberi had resulted from a. polished rice diet in long been a common and a serious birds resembled beriberi in man. disease in parts of the world where He believed that rice contained too polished rice was the staple food. much starch, which poisoned nerve Ghristiaan Eijkman, a Dutch surgeon, cells, and that the outer layers, re- was carrying out studies on fowls in a moved from the grain in milling, were military hospital in Java in the 1890's. an antidote. His report was published To save money, he fed them scraps— in Dutch, and some time elapsed mostly polished rice—from the pa- before it was known generally. tients' meals. The fowls unexpectedly G. Grijns, another Dutch physician, developed a bad nerve ailment, which interpreted Dr. Eijkman's findings in a resulted in paralysis. different way. He concluded in 1901 Somewhat later the director of the that beriberi in birds or man was due hospital withheld permission to use to a deficiency or absence of an essen- the scraps, and Dr. Eijkman had to tial nutrient from the diet. buy natural or undermilled rice for From then on, chemists in many the chickens he used in his experi- countries tried to concentrate the ments. The ailing birds improved substance in rice that prevented beri- after they began eating the natural rice. beri in order to obtain it in pure form. Dr. Eijkman then began a series of Among them was Casimir Funk, of the experiments that led to the first clear Lister Institute, London, who coined concept of disease due to nutritional the term "vitamine" and applied it to deficiency. He fed polished white rice the antiberiberi substance. to pigeons, chickens, and ducks. They B. G. P. Jansen and W, P. Donath developed the paralysis he had ob- in Holland in 1926 isolated the anti- served previously, and they recovered beriberi vitamin, and in the 1930's 139 140 TEARBOOK OF AGRICULTURE 1959 Robert R. Williams and his associates A LACK OF VITAMINS of the B complex determined its structure and synthe- is one of the forms of malnutrition that sized it. often occur throughout the world. Be- Thus men discovered the cause and cause of the similar distribution of the cure of beriberi, which nevertheless B vitamins in foods, a deficiency of remains a serious disease today in several factors is observed oftener than countries in which overpolished and a deficiency of a single substance. The overmilled rice is a staple in the diet. interrelationship of many of these vita- During the first stages of separating inins in life processes means that signs and identifying vitamins, the designa- of deficiency often are similar when tion 'Svater-soluble B" was given by the diet lacks any one of several factors. Dr. Elmer V. McCollum and Mar- Many physiologic and pathologic guerite Davis to the concentrates stresses influence the need for the B that cured beriberi. Vitamin B at that vitamins. Larger amounts are needed time was thought to be a single sub- during growth and in pregnancy and stance. Later research showed that it lactation than in maintenance of consists of a number of substances that health in adult life. The requirement differ widely in chemical structure may be increased by diseases that but have much the same natural elevate metabolism and by conditions distribution in foods. associated with poor absorption, im- Of the 11 substances in the vitamin proper utilization, or increased excre- B complex that now are available in tion. Administration of antibiotics may pure form, five are components of one lead to vitamin deficiency in some or more coenzymes—thiamine, ribo- circumstances; in others, antibiotics flavin, niacin, pyridoxine, and panto- spare vitamin requirements. thenic acid. Coenzymes are catalysts that have important and often related THIAMINE, or vitamin Bi, also known functions in the biochemical processes as the antineuritic or antiberiberi vita- by means of which nutrients are used min, is a water-soluble compound. It for energy and for building up or is readily broken down by heat in maintaining the cells and tissues of neutral or alkaline solutions. Its solu- the body. bility and the ease with which it is Two of the B vitamins, folie acid and destroyed are important, because over- vitamin B12, have antianemic proper- cooking food and discarding the v/ater ties and presumably exert their func- in which the food is cooked may cause tion in a similar way—that is, as large amounts of the vitamin to be lost. coenzymes. Thiamine is present in many natural These seven vitamins are essential foods but is abundant in few. Lean in human nutrition and must be pork is one of the best sources. Dry included in the daily diet. beans and peas, certain of the organ Of the other four members of the B meats, and some nuts furnish sizable complex, choline is important in amounts. Whole wheat and enriched human nutrition but is probably not cereals and bread are dependable an essential dietary constituent be- sources. They can contribute valua- cause the body can form it from other ble amounts to the diet. The small compounds. amounts provided by other foods, such Very likely biotin is required, by as milk, eggs, other meat, fruit, and man, but it is furnished by bacterial vegetables, add up and represent a synthesis in the intestinal tract as well worthwhile contribution to the diet. as by food. The thiamine requirement is related Inositol and p-aminobenzoic acid, to caloric intake. The minimum need other members of the B complex, have is approximately 0.20 to 0.23 milli- not been shown to be essential in gram per 1,000 Calories. This require- human nutrition. ment is based on experiments in which VITAMINS OF THE B COMPLEX 141 thiamine in the diet is restricted, on ministration of glucose and by exercise studies of diets of population groups, and form the basis of a diagnostic test and on estimates of the amounts ex- for thiamine deficiency. The concen- creted in the urine of people having tration of glucose, lactic acid, and known intakes of thiamine. pyruvic acid in blood is determined The requirement of infants in rela- after the administration of glucose and tion to Calories appears to be compa- a standard amount of exercise. Results rable to that of the adult. Human milk are expressed as a ''carbohydrate in- supplies an average of 0.21 milligram dex," which increases in thiamine de- per I, 000 Calories. We have evidence ficiency. that the ratio of carbohydrate to fat Thiamine deficiency has been pro- in the diet influences the requirement. duced experimentally in people. Ef- The recommended dietary allow- fects of a moderate shortage of thia- ance for thiamine is 0,5 milligram per mine include fatigability; apathy; loss 1,000 Calories. When an adult's diet of appetite; nausea; such psychic and furnishes fewer than 2,000 Calories a personality disturbances as moodiness, day, the thiamine allowance should irritability, and depression; a sensa- not be less than i milligram daily. tion of numbness in the legs; and ab- This allowance provides a large factor normalities of the electrocardiogram. of safety above the minimum, need and Advanced deficiency of thiamine, or seems desirable because requirements beriberi, is characterized by peripheral vary among individuals and because neuritis, heart disease, and edema. stores of thiamine in the body are not Peripheral neuritis is a disease of the large and may be exhausted readily in nerves of the extremities; usually both diseases associated with an increase in legs are afifected and sometimes the metabolism. arms as well. The symptoms include Bacteria in the intestines may syn- loss of sensation, muscle weakness, and thesize some thiamine, but the amount paralysis. available to the human body to sup- A deficiency of thiamine can also plement the dietary supply seems to be cause damage to the brain, which may small. be manifested by confusion, delirium, Thiamine is absorbed readily from and paralysis of the muscles that move the intestinal tract. It is excreted in the the eyeballs. This condition is called urine in amounts that reflect the Wernicke's syndrome. amount taken in and the amounts stored in tissues. Measurement of the RiBOFLAViN, formerly known as vita- urinary excretion of thiamine after min B2 or G, is a water-soluble, yellow giving a small dose of thiamine is use- pigment. It is widely distributed in ful in determining whether body stores foods of plant and animal origin. It is are adequate or deficient. stable to heat, especially in acid solu- Thiamine functions in the body as a tions, but it is destroyed on exposure coenzyme, which is called cocarboxyl- to fight. ase. It acts as a catalyst in one of the Among the best sources of riboflavin chemical reactions by which glucose are milk and variety meats, like liver, (sugar) is broken down in the tissues to heart, and kidney. Other lean meat, supply energy. These reactions proceed cheese, eggs, and many of the leafy, stepwise, and cocarboxylase acts at an green vegetables also furnish valuable intermediate stage when a substance amounts. Whole-grain and enriched known as pyruvic acid has been formed. cereals and bread, in the amounts in In thiamine deficiency, pyruvic acid which they are eaten in this country, accumulates in the blood and tissues contribute important amounts of ribo- and there is a change in the ratio of flavin to the diet.