History of Research on the Nutritional Value, Biochemistry, and Medicinal Uses of Soybeans and Soyfoods - Page 1
by William Shurtleff and Akiko Aoyagi
A Chapter from the Unpublished Manuscript, History of Soybeans and
Soyfoods, 1100 B.C. to the 1980s
©Copyright 2004 Soyinfo Center, Lafayette, California
Many references to food and its relation to health and longevity exist in man's earliest writings. In this chapter we will first discuss nutritional discoveries related to soyfoods made in East Asia prior to the scientific era. Then we will discuss scientific discoveries that began in Europe in the mid-1800s and were soon being made worldwide.
SOYFOODS NUTRITION IN TRADITIONAL EAST ASIAN DIETS
Although scientific studies on soybean nutrition did not begin until the 1880s, important discoveries had been made long before that time by people in East Asia closely attuned to the needs of their bodies. In fact that case could well be made that most of the important discoveries concerning soybean nutrition were made in ancient times, only to be rediscovered, elucidated, and quantified by modern nutritionists, doctors, agricultural economists, and students of world food supplies. The following represent important nutritional discoveries:
1. Need for Cooking to Maximize Nutritional Value. Records show that soybeans used for food (and even occasionally for work-animal fodder) have always been cooked. Raw soybeans do not taste good. The cooking times for most traditional soyfoods that were required to give them a good flavor and/or texture generally exceeded those later recommended by modern nutritionists as necessary to inactivate trypsin inhibitors and maximize digestibility. Western nutritionists did not fully understand the importance of cooking (especially soybean meal for livestock feeds) until the mid-1930s.
2. The Cereal-Legume Protein Model to Maximize Protein Quality. The classical protein combination of cereal grains and legumes in proper proportion has sustained most traditional societies throughout history. Modern nutritionists now realize that this combination, because of protein complementarity, can increase the protein quality of the combination by up to 40% at no extra cost. In East Asia soyfoods have always been consumed as part of a grain-based diet. The traditional grains were rice throughout (in ancient times mostly in south China, northern Japan, and Indonesia); wheat (as bread or noodles) and millets in north China; and barley in parts of Korea and southern Japan. The balance was typically 70-80% cereal grains and 20-30% soy, the very balance that nutritionists have more recently found to maximize protein quality and quantity.
By understanding other traditional application of the cereal-legume model, we can perceive how soyfoods might easily be introduced into traditional societies without disrupting the basic dietary patterns. Latin Americans combined corn tortillas with frijoles in the north and rice or corn with black beans (feijoas) in the south. Middle Easterners combined pita bread and bulgur wheat with chick-peas (garbanzos) to make falafels with hummus sauce. Indians combined rice or chapatis (unleavened flat breads) with dal (split, dehulled pulses), often served with yogurt, or fermented together as with idli (steamed sourdough rice-and-dal bread) or dosa/dosai (sourdough rice-and-dal pancakes). Native Americans combined corn and beans to make succotash. Modern Americans combined wheat and peanuts in the popular peanut butter sandwich. The natural and inherent knowledge of nutrition in people's bodies apparently understands protein combining.
3. The Cereal-Legume Protein Model to Maximize Protein Quantity. The animal protein model, now the basic standard in affluent Western societies, has rarely existed in traditional societies since it makes such wasteful use of basic food and land resources and increases the price of protein. Thus in East Asia, where population densities have long been among the highest in the world, soyfoods and cereal grains have always been used in combination and consumed directly, to optimize the earth's ability to produce protein and to keep the cost of the diet as low as possible. As the effects of world food shortages and rising food prices become more acutely felt in the Western world we may expect a gradual shift from the meat-and-dairy diet (which wastes large amounts of energy and water as well as basic food resources, as they are run through livestock) toward the traditional cereal-legume diet, with soyfoods as a key protein source. Interestingly, we may be able to combine the two models and integrate them into the "balance meal model" by using soyfoods meat and dairy analogs in place of meats and dairy products.
4. The Cereal-Legume Protein Model to Reduce Degenerative Diseases. There is abundant evidence to show that the traditional cereal-legume protein model gives a diet that leads to better health and longevity than diets based on the animal protein model. The latter, partially because it leads to such high intakes of saturated fats and cholesterol, is now considered a major contributing factor in coronary heart disease, cancer of the colon and breast, diabetes, and stroke. In 1949 Dr. A.K. Smith of the USDA wrote that "China gives a wonderful illustration of the effects on the human race of a vegetarian diet over a long period of time. In fact, the state of nutritional equilibrium which has been attained in eastern Asia on a vegetarian diet is unique and could no doubt serve as a source of valuable nutritional data." J.L. Buck's extensive survey of farm family diets in China from 1922-25 found an average daily consumption of 3,461 calories per adult male farmer; this diet was shown to contain an adequate protein supply (Buck 1930). In 1931 William Morse reported that 97% of all Japanese food came from plant sources, 2% from the sea, and 1% from meat (Dorsett-Morse 1931, p. 7008). Yet in 1981 it was announced that the Japanese had the greatest longevity of any country in the world. In 1960 they obtained 69.5% of their protein from plant sources, 21.5% from fish and sea vegetables, and a mere 9% from meats, eggs, and milk; 15.6% came from soyfoods.
Some Westerners have noted that most people from East Asia who have traditionally eaten a grain-and-soy diet are of smaller stature than most Westerners, and they assume that this indicates an inadequacy in the diet. This pervasive assumption that "bigger is better" will not withstand careful scrutiny. It should be obvious that good health and longevity are infinitely more important than large body size. The latter can be increased by excess consumption of protein and calcium. Yet traditional diets, as long as they are adequate in calories, generally lead to better health and longer life than standard Western diets. And they are less expensive and make better use of the world's food resources.
5. Food Processing Techniques to Reduce Flatulence. Throughout East Asia, soybeans are only rarely eaten as boiled beans, both because they take a lot of time and fuel to prepare and because they cause gas. Rather simple but ingenious processes have been developed to reduce or eliminate these flatus factors (now known to be oligosaccharides, complex carbohydrates). In tofu, these are lost in the soybean soak water, the whey, the okara, and the tofu soak water. In tempeh, miso, and natto, they are virtually eliminated by the combination cook and fermentation.
6. Medicinal uses of the Soybean. In ancient China, the soybean was regarded as having many medicinal virtues, and was included as a preventive medicine in the second class of drugs. In the famous Materia Medica Pen Ts'ao Kang Mu , written by Li Shih-chen in 1597, the soybean is stated to be a specific remedy for the proper functioning of the heart, liver, kidneys, stomach, and bowels. It was also used as a specific remedy for constipation, as a stimulant for the lungs, for eradication of poison from the system, improving the complexion by cleaning the skin of impurities, and stimulating the growth and appearance of the hair. Fresh green soybeans and black soybeans were each ascribed a number of medicinal properties, and to this day black soybeans are widely used by Chinese doctors to strengthen the blood (see Chapters 8 and 9).
MODERN RESEARCH ON SOYFOODS NUTRITION
Protein Overview . Although the word "nutrition" first appeared in English in 1615, it was not until the development of modern science in the 18th and 19th centuries that the essential nature of certain nutrients in human diets began to be appreciated. Between the years 1775 and 1850 it was understood that protein, oxygen, calcium, iodine, and a scurvy-preventing factor (later called vitamin C) were essential.
The word "protein" was first used in a published work in 1838 by the Dutch agricultural chemist Gerard Mulder (Ref??). It was derived from the Greek word meaning "of first importance." Mulder considered protein to be a basic substance found in all living matter, and to have three forms: albumen, caseine, and fibrine. Even before that date, in 1820, glycine and leucine had been discovered, but it was not until 1848 that Berzelius (Ref??) had suggested that these and related compounds, each containing a carboxyl and an amine molecule, be called "amino acids." Twelve amino acids had been discovered by 1900. Methionine was discovered in 1922 and, the 19th and last (?? aren't there 20-22 now??) amino acid, threonine, was discovered in 1935.
During the late 1800s the exact nature of proteins was not clear. Because they seemed to resemble egg white or albumen (a term first used in 1599), they came to be referred after 1859 as "albuminoids" (or eiweiss , "egg white" in German) and after 1871 as "proteids." As the nature of the various proteins and their constituent amino acids came to be clarified in the late 1800s and early 1900s, these earlier and less precise terms fell into disuse.
The First Food, Agriculture, and Nutrition Revolution, 1850-1920 . During this period, dietary patterns were first evaluated and popular interest in human nutrition was first heightened. The first work with soyfoods nutrition, aimed at understanding the chemical composition of the soybean seed and later of various soyfoods, began in Europe but soon spread to Japan. In 1869 Dr. W.O. Atwater (Ref??), one of the pioneers of modern human nutrition, published the first analysis of an American food (corn), and in 1896 (Ref??) he published the first US tables showing the composition of familiar foods. Descriptions of the standard American diet of the 1880s were remarkably similar to those of the 1980s; both patterns were considered to be too high in calories, fat, sugar, and salt. Reform movements began and consumer interest in nutrition in general and particularly in vitamins, minerals, and nutritious (or health) foods was apparently as high then as it was during the 1970s (Jerome 1981; see also Chapter 41.1).
1855 Fremy, French professor of chemistry and former director of the National museum, did the first known nutritional analysis of soybeans. He investigated the nutritional/chemical composition of soybean seeds brought from China by M. de Montigny and gave appraisal of the oil extracted from them (Paillieux 1880).
1872 Senft in Germany published chemical/nutritional analyses of soybean seeds, which were published by Haberlandt in 1877. In 1878 Haberlandt published, in addition, an analysis by Schroeder, a chemist in Napagedl, and a chemical analysis of the entire plant by Caplan of Vienna.
1880 Pellet, a French chemist, published a detailed chemical/nutritional analysis of three soybean seeds, one each from China, Hungary, and France. These had been sent to him by the Society for Acclimatization (see Chapter 32). The seeds were reported to contain an average of 9.6% moisture, 31.7% protein, and 15.7% fat, plus a small amount of starch. Pellet also gave a detailed analysis of the soybean's ash (minerals), showing that it was especially rich in phosphoric acid and potassium. These results were publicized in 1880 by Paillieux, who also mentioned (without citation) that Champion and L'Hote^ had given partial analyses of some soyfoods.
1881 Levallois in France did a brief study of the carbohydrates and sugars contained in soybeans; he identified galactan.
1883 Meissl and Boecker in Germany published by far the most extensive and systematic study of the chemical/nutritional components of the soybean seed. In the first published work on the isolation of soybean proteins, they distinguished three such proteins: soluble "soja casein" comprised 30% of the total soybean and more than 90% of the total protein content, insoluble soja casein comprised 7% of the soybean, and "soja albumin" comprised a mere 0.5% of the soybean. They considered the latter protein to be a transformation product of soja casein. They also analyzed the soybean's ash and (in great detail) the soybean's oil, stating that it contained lecithins, cholesterins, waxes, and gums; it was mostly neutral triglycerides with almost no free fatty acids. Soybeans contained no gluten and no more than 3% starch. Their experiments were done in 1880, but publication was delayed.
1883-1884 Hanausek reported finding a small amount of starch in the soybean, deposited where the surface of the cotyledons (the two halves of the soybean) meet. He saw the starch grains under a microscope.
1885 Harz, in Germany, found that immature or fresh green soybeans, or those allowed to mature after the vines were cut, may contain starch in some varieties, but that mature soybeans were practically starch free.
1885 Japanese scientists began a series of elaborate digestion experiments on diets containing rice and soyfoods. These were the world's first studies on soyfoods and human nutrition. The first results were published (all in Japanese) in 1887. K. Osawa and Ueda (1887), Osawa (1889), and T. Suchi (1887??, 1888), at the Physiological Institute of the University of Tokyo, and Mori and Kellner (1887) all studied the digestibility of diets containing tofu and shoyu (soy sauce). Note that Kellner, a German, was thus the first Westerner to study soyfoods and human nutrition. Tahara and Kitao (1887??; 89??) investigated the various forms of nitrogen and proteins in Japanese shoyu. Similar tests were done by Nagai and Murai in 1897. In 1899 Kano and Iishima of Tokyo Army Medical College investigated the digestibility of tofu, okara, yuba, and shoyu. All these studies, which showed very high soy protein digestibility (about 95%), were first reported in English by Oshima in 1905.
1886 Stingl and Morawski reported the presence in soybeans of a diastatic ferment (now called "amylolytic enzyme") which transformed starch (including the small amount of starch they found in the soybean) into 2 parts sugar (glucose) and 1 part dextrin. In 1880 Stingl and Gruber (Ref??) had taken out a patent for the use of soybeans and their enzymes in the manufacture of yeast. In 1887 Morawski and Stingl reported on the sugars in the soybean. What did they say?? Did they describe them??
1886 Paillieux, after reporting that he had analyzed soybeans and found them to contain no trace of starch, first advocated their use in diabetic diets. ( Bulletin of the Society for Acclimatization , p. 187).
Diabetic Diets and Soyfoods, Developments. Diabetes mellitus is a metabolic disorder in which the body is unable to metabolize sugars and other food materials efficiently. It appears when there is a relative deficiency of insulin (a hormone produced by the pancreas) in the blood. Adult onset diabetes is less severe than juvenile onset. In 1921 insulin was discovered and since 1922 it has been used by diabetics to reduce high blood sugar concentrations by promoting the formation and storage of glycogen, a complex sugar.
Diet has always been the cornerstone of diabetic therapy. In the late 1800s diabetics were advised to try to avoid starches; later more emphasis was placed on avoiding quickly absorbable carbohydrates such as simple sugars, the monosaccharides and disaccharides. Noncaloric sweeteners and fructose are favored. By 1978 diabetes was the number three cause of death in the US. It was associated with obesity in 60-80% of the patients.
Early studies on soybeans, starting with that of Pellet in 1880, found little or no starch; most other beans, however, were known to contain large amounts of starch. Pellet (1880), Meissl and Boecker (1883), Hanausek (1883-84), and Stingl and Morawski (1886) reported small amounts of starch (1-3%) in soybeans. Paillieux (1886), Blondell (1888), Inouye (1895), and Prinsen Geerligs (1895) found no trace of starch, and Harz (1885) did not find any except in immature beans.
The soybean first became known and widely used as a food in Europe and later in America as part of diabetic diets. Paillieux, who had first suggested the use of soybeans in diabetic diets in 1886, played an active role in implementing his suggestion and publishing related events in the Bulletin of the Society for Acclimatization . In May 1888 Lecerf and Dujardin-Beaumetz (the former was a first-class pharmacist) reported to the Society of Practical Medicine in France concerning tests on the use of soybeans in bread and biscuits for diabetic diets. The bread was reported to have an excellent flavor and be greatly superior to gluten bread. These tests were apparently?? conducted by Dr. Dujardin-Beaumetz at the Cochin Hospital. Then in 1890 Dr. Dujardin-Beaumetz spoke to the members of the Society for Acclimatization about the soybean and its value in diabetic diets. In 1888 Egasse wrote at length about soy in diabetic diets. He mentioned that Dr. Dujardin-Beaumetz' low-starch "soy bread" (as it came to be called) was like a gingerbread with a thick, brown crust. It had the disadvantage of, after a certain time, creating a dry sensation in the mouth, followed by thirst. According to an analysis by Lecerf, the bread contained 45% moisture, 20.2% protein, 9.4% fat, 2.8% starches and sugars, and 0.86% phosphoric acid. Already an industrialist in Riems, Mr. Bourdin, had started to market a gluten-soy bread called "pain de soja gluten;" Egasse disliked its relatively high carbohydrate content. A Mr. Laillieux, a former intern at the Dey hospital in Algiers, Algeria, told Egasse that numerous Arabic patients were being treated successfully with a soy pap preparation (]explain??). In 1890 Dr. Menudier wrote of the value of soy bread in diabetic diets. In 1894 A.M. Villon wrote of the new bread as "Asian Bread" and said that a Mr. Ledeuil of Baune, France, had started to make it. Villon visited his plant, saw how the soy bread was made, and did a nutritional analysis, showing that it contained only 11.4% carbohydrates. He concluded "The result of these analyses is that Asian Bread is twice as rich in protein and contains one-fifth the starch as wheat bread. This, added to its good flavor, makes it a valuable product for combatting diabetes." Interestingly Villon called the soybean "Haricot Chinois" throughout his article. In 1909 Chevalier wrote an article on "Soy and Gluten Breads for Diabetics" in a French medical journal. In 1909 (Ref??), 1910, 1911, and 1919 Le Goff wrote four long articles on the use of soybeans in diabetic diets for a French hospital gazette. He encouraged the French to grow their own soybeans and gave four recipes for their use in diabetic diets; whole dry soybeans with butter; soybeans sauteed with vegetables; cooked soybean puree; and bread or cake with soy.
Prior to 1906 the use of soy in diabetic diets was known only in France, and it was one of the first ways that the soybean began to be used as a food. In that year in an article on "Diabetic Diets," Winton, of the Connecticut Agricultural Experiment Station, first discussed the value of the soybean as a dietetic food in the US, and mentioned that a soybean meal was being made commercially by the Theo. Metcalf Co. in Boston for use in diabetic Diets. The two types of Metcalf's Soja Bean Meal were advertised as containing 5.5 and 7.6% starch. Winton gave a recipe for use of the meal in a Homemade Diabetic Biscuit. Metcalf's meal may have been the first commercial soyfood in America (unless there was a previous soy coffee??). Ruhrah^ (1909 Ref??, 1910, 1911b) and Friedenwald and Ruhrah^ (1910), both American pediatricians, used soy flour (made by the Cereo Co. in Tappan, New York) in the treatment of at least eight cases of diabetes. They concluded that "The soy bean is a valuable addition to the dietary of the diabetic on account of its very low starch content, palatability, and the numerous ways in which it can be prepared. It causes a reduction in the total quantity of sugar passed in diabetic subjects."
In 1928 Dr. Jozef Szanto, a Hungarian, wrote a pamphlet and a Hungarian journal article on soy flour in the treatment of diabetes. He reported success in treating diabetic patients in his sanitarium. In the years that followed, soy flour came to be widely used in diabetic diets worldwide, but the increasing use of insulin after 1922 decreased the emphasis on and urgency of dietetic solutions to the problem??. In Japan, since the early 1900s, tofu and soymilk have been part of the standard diabetic diet. Tofu is especially valuable, since it contains less sugars than soymilk.
1888 Blondell in France, the first soybean physiologist, did detailed studies on the anatomy and physiology of the soybean seed, which he accompanied by lucid illustrations. He reported the total absence of starch in all parts of the seed.
1889 Kellner , a German teaching in Japan, did the first nutritional analysis of tofu and of four types of miso. He also analyzed three types of soybeans.
1889 Goessmann , at the Massachusetts Agricultural Experiment Station, did the first American analysis of the soybean, both of the seeds and the whole plant, for use as fodder. Many similar analyses were done at US agricultural experiment stations during the next 15 years. Goessmann later showed that the digestibility of soybean protein and fats averaged 90%. (Provide figures for other foods??)
1889 Schulze in Germany gave a detailed nutritional analysis of etiolated soy sprouts, bleached from lack of sunlight.
1894 Schulze and Frankfurt first?? reported the presence of sucrose in soybeans. Why significant??
1895 Yabe in Japan published, in German, an analysis of the proteins in natto. This was the first known analysis of a Japanese soyfood by a Japanese. The data were published in English by Yabe in 1897 Ref??
1895 Inouye did the first nutritional analyses of frozen tofu, yuba, and soymilk. He compared the latter with cow's milk.
1895 Prinsen Geerligs , a Dutchman in Indonesia, did a nutritional analysis of three types of soybeans, tofu, soymilk, soy sauce, and miso. He did not find any starch in the soybeans. In 1896 his original Dutch study was published in German.
1896 Trimble in the United States summarized much of the earlier studies done on soybean and soyfood nutrition in the American Journal of Pharmacy . This was the first such publication in America to reach a wide audience.
1897 Osborne and Campbell , of the Connecticut Agricultural Experiment Station, published "Proteids of the Soy Bean," the first detailed analysis done in America. They isolated and purified several protein fractions and found that the chief protein fraction was a globulin, which they named glycinin, and defined as that fraction of the total soy protein extractable with 10% sodium chloride solution which precipitates on dialysis of a meal extract against water. They analyzed the proportions of elements in glycinin, showed it was different from legumin (a protein found in some beans), and also reported the presence of legumelin. No mention was made of amino acids. In 1898 this pioneering study was republished in the Journal of the American Chemical Society . Here they recommended a conversion factor for the nitrogen in the glycinin fraction of 5.71. Explain??
1897 Langworthy of the USDA published a collection of earlier nutritional analyses of soymilk, fresh tofu, frozen tofu, natto, miso, yuba, and shoyu; each has been cited above. This was reprinted by Abel of the USDA in 1900.
1899 Rein was the first to compare soy and animal proteins, stating, "In point of nutriment, the soy-bean is of all vegetables the nearest to meat."
1899 Blasedale , a chemistry instruction at the University of California at Berkeley, did nutritional analysis of black and yellow soybeans; he found no starch.
1903 Lechartier , director of the agricultural station at Rennes, France, made perhaps the most extensive investigations of the nutritive and ash (mineral) constituents of all parts of the soybean plant. He was the first to measure the important mineral calcium, showing the soybean seed to contain 0.24-0.34%. Later reports by Forbes (1909), Osborne and Mendel (1917a, b, c), Bowers (1919), Adolph (1922), and Horvath (1928), gave values of 0.18-0.27%. Horvath noted that, compared with most other seeds, the soybean was very rich in calcium.
1905 Oshima , Director of the Hokkaido Agricultural Experiment Station in Japan, gave an extensive review of Japanese investigations on human nutrition, including numerous studies on the digestibility of the protein and carbohydrates in soyfoods, including tofu, yuba, okara, and whole dry soybeans. Published by the USDA, this report reached a wide audience. It was the first report in the West on soyfoods and human nutrition.
1905 Korentschewski and Zimmerman found soy oil to be highly digestible.
1907 Suzuki, Aso, and Mitarai did the first nutritional analysis of Japanese shoyu??
1907 Osborne and Clapp at the Connecticut Agricultural Experiment Station, fractionated the soybean into glycinin, its major protein, plus small amounts of legumelin and proteose. They then hydrolyzed the glycinin and did the first analysis of the soybean's amino acids, which they found to be very similar in quantity to those reported for casein, the principal protein of milk. Methionine and cystine, which had not yet been discovered, were not shown.
1907 Bloch , a pharmacist/chemist for the French colonies, did a comprehensive review of soyfoods nutrition, with an elaborate table showing all of the nutritional/chemical analyses of the soybean seed to date (35 analyses in 16 publications), including analyses by Muntz, Nikitin (Russian), Lipski (Russian), Giljaranski, and Koenig not mentioned above. Bloch concluded: "The food value of soy is incontested and, if one takes these analyses as valid, it is superior on an equal weight basis to lean beef." He then compared the nutrients of soybeans and beef in tabular form. 1907 Bloch and Klobb found a sterol (a phytosterol) in soybeans, which they named "sojasterol." This was further explored by Matthes and Dahle in 1911.
1906 Katayama did the first nutritional analysis of soymilk.
1909 and 1910 Ruhrah did the first US studies with soyfoods and human nutrition, and was the first pediatrician to use soybeans in infant feeding. He reported his work to the American Pediatric Society. He dehulled soybeans, ground the cotyledons to a fine flour, added 1-6 tablespoons per quart of water (or water-milk mixture) with a little salt, boiled it for 15 minutes, and fed it with good results to infants with diarrhea, digestive disturbances, or diabetes. He concluded that soybeans would be "a valuable addition to the dietary of the sick infant." Friedenwald and Ruhrah^ (1910) continued these experiments, and that year Ruhrah^ published the first analysis of whole (full-fat) soy flour, a product made for their use by the Cereo Co. The analysis showed no starch to be present. In 1915, after considerable experimentation, Ruhrah recommended the following for use when fresh milk was not available, when its sanitation was questionable, or when a baby had vomiting or diarrhea: combine 1 quart of water, 1 tablespoon soy flour, 2 tablespoons barley flour, and a pinch of salt. Boil for at least 20 minutes, replace the water lost in cooking, add 1-2 parts condensed milk to 16 of the gruel, and feed 2-8 ounces per feeding to babies every 3 hours. In 1916 Sinclair fed a soy gruel/soymilk similar to that used by Ruhrah to 74 infants who had diarrhea; 44 recovered well.
1909 Yoshimura did the first nutritional analysis of tamari shoyu.
1909 Takeuchi , in Tokyo, investigated soybean enzymes and found a very
active urease, which he considered to be the main enzyme. It breaks down urea, liberating ammonia. Did he show this? Significance??
1911 Mendel and Fine of Yale University did the first systematic study in the US on the utilization and digestibility of soy protein. In a 6-day experiment on one adult, whole soy flour, supplying 90% of the total nitrogen intake, was boiled for 30 minutes and served with tomatoes. The total nitrogen was 85.3% digested (as compared with 77.9% for navy beans). They also did nitrogen-balance experiments (see below for explanantion) with soybeans on dogs, but found that soy protein was less well utilized than meat.
1911-12 Li Yu-ying and Grandvoinnet , in France, in their long chapter on "The Soybean as Human Food" in The Soybean , gave a thorough review of all known research on soyfoods nutrition and on the chemical/nutritional composition of the soybean. They discussed the place of soyfoods in vegetarian diets and were the first to mention that soyfoods alkalize the blood (a key concept in traditional Asian nutritional thought) and, unlike meats, contain no metabolic waste materials such as uric acid, purine bodies, creatinin, and the like. Some writers in the late 1930s (Kale 1936; Ferri 1938) cited this latter point, noting that uric acid from meats can cause rheumatism, kidney troubles, and gout.
Vitamins, Overview . The term "vitamin" appeared rather late in the history of nutrition. Its predecessor, "vitamine," was coined in 1912 by a young biologist, Dr. Casmir Funk, who proposed that a number of diseases such as beriberi, pellagra, scurvy, and rickets were caused by a lack of special nutrients in the diet. The spelling of the term was changed to "vitamin" in 1920. Actually, however, understanding of deficiency diseases can be traced back to 1753, when James Lind, a Scottish naval surgeon, published his famous report showing that oranges and lemons prevented and cured scurvy. New progress in the field was made in 1897, when Dr. Christian Eijkman produced a toxic condition in birds by feeding them polished (white) rice, then promptly cured them by feeding them the rice polishings. Substances later known as vitamins C and A were discovered in 1912 and 1913. Great progress was made in the following years. The first study of vitamins in soybeans was done in 1915.
World War I and Soy Nutrition, Overview . The period from 1914-1918 and several years thereafter was one of intense research on soyfoods nutrition in the US as the soybean, for the first time in American history, came to be widely used as both a protein source and an oilseed.
1915 Street and Bailey did the first comprehensive study of the soybean's carbohydrates and enzymes. They isolated 10 different carbohydrates including starch (0.5% of the total soybean composition), raffinose (1.13%), and sucrose (3.31%). They also found a protease (an enzyme that can break down proteins) in soybeans.
1915 Osborne and Mendel , now two of the most respected protein researchers in the world, did some of the first work on limiting amino acids and protein complementarity using soy proteins. They published many rat growth curves to demonstrate that various combinations of amino acids had vastly different effects on growth.
1917 Daniels and Nichols , two women at the University of Wisconsin, studied the overall nutritive value of the soybeans, including vitamins, minerals, enzymes, proteins, and carbohydrates. They found that "the protein of the soy bean appears to be quite as valuable as the casein of milk," and that "from an economic point of view, the soy bean is one of the most valuable legumes." Using rats, they did the earliest known studies on (1) the use of soy flour to complement the proteins in wheat flour, (2) the bioavailability of minerals in the soybean, and (3) the vitamins in the soybean. They showed soybeans to be a good source of B vitamins??
1917 Osborne and Mendel , based on almost 20 years of research with soy proteins, published their most famous work, "The Use of Soy Bean as Food." In the first controlled tests of feeding soybeans to rats, they showed that whereas raw soybeans failed to support their growth, the rats grew well when the beans were cooked with moist heat (as in a steam bath). This first observation that moist heat treatment is needed to develop maximum nutritive value, understood for millenia in East Asia, was later confirmed and extended by an extensive body of scientific literature (Liener 1958) and is still the basis for present day processing of soy protein foods and feeds. Osborne and Mendel thought the improvement in protein quality was due entirely to improved palatability from the moist heat treatment. Several generations of nutritionists thereafter were kept busy trying to explain why the moist heat was beneficial. Osborne and Mendel did not define the exact heat and moisture requirements to produce optimum nutritional value; such studies were later done or summarized by Klose et al. (1948), Borchers et al. (1948), Smith et al. (1964), and Rackis (1965, 1966 Ref??).
Osborne and Mendel also reported that (1) soy protein had qualities unlike those of other leguminous seeds so far investigated, since rats grew and bred well on diets containing moist-heated soybean meal, commercial presscake, or glycinin as the sole protein source; (2) the soybean was the only known seed that contained both water soluble and fat soluble vitamins; (3) the soybean was a relatively poor source of calcium; and (4) in America soybeans were being used almost solely in diabetic diets. In two other publications in 1917 on corn and soybeans, they showed that if corn protein was supplemented with soy protein, the growth of rats was satisfactory, which it was not on corn protein alone.
Protein Quality, Overview (1880-1920) . In the late 1800s Western research scientists had succeeded in isolating pure proteins and separating them from whole foods. They soon found that there were many proteins. In the early 1900s they discovered that each of these proteins was composed of a finite number of building blocks, amino acids. Some of the first information on how the amino acid composition of a protein determines its biological value or nutritional quality came from the pioneering experiments of Dr. Thomas Osborne and Dr. Lafayette Mendel in feeding isolated proteins to rats. In about 1911 they started to work together at Yale University. Osborne, based on his work with soy proteins, contributed the skill required to isolate the pure proteins. Mendel supervised the feeding experiments. It was found that with some proteins (such as casein from milk or glycinin from soybeans fed as the sole protein source), the rats remained healthy and grew well, whereas with others (such as gliadin from wheat) they maintained their weight but did not grow much, and with still others (such as zein from corn), they were unable to grow, lost weight, and eventually died. Proteins such as casein and glycinin that supplied all the amino acids needed for growth came to be called "complete proteins;" those like glianin were said to be "partially incomplete;" and those such as zein, which supported neither growth no maintenance, were called "incomplete."
By 1915 Osborne and Mendel realized that each protein had a limiting amino acid, the one in shortest supply relative to the needs of the animal consuming it, and that this, like the weakest link in a chain, determined the quality of that protein. They also realized that by combining one food having a certain limiting amino acid with another food having an abundance of that amino acid (a principal called "protein complementarity") they could create a mixture whose protein quality was higher than that of either of the individual foods.
It was soon realized that a more exact, quantitative measure of protein quality was needed. In 1919 the first such measure, Protein Efficiency Ratio or PER was proposed by Osborne, Mendel, and Ferry Ref??. How is it determined?? Again, rats were fed a diet in which protein was the only factor limiting growth. In 1981 PER was still the most widely used test in the US for protein quality. A second technique, the nitrogen balance method (explain??), was proposed by H.H. Mitchell in 1924 (Ref??), based on a method first described by K. Thomas in 1909 Ref??. While PER applied only to growing animals, the nitrogen balance method could be used on adults, and was especially well suited for humans. It should be noted that the two methods were based on very different basic assumptions. The first assumed that a protein which made an animal grow rapidly was of good quality. The second emphasized balance rather than growth. Interestingly, the two methods yield results which are highly correlated with each other (r = +0.83) and with expectations based on amino acid composition.
1918 Lyman and Bowers studied the digestibility of bread made with soy flour; the digestibility of the soy protein was reported to average 91.1%, and the soybean carbohydrate to average 96.5%.