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health claim states, “25 grams of soy protein a day, as part of a diet low in
saturated fat and cholesterol, may reduce the risk of heart disease. A serving
of [name of food] provides [amount] grams of soy protein.” Since then, the
range of foods that include soy protein has been limited only by the imag-
ination of food scientists and marketers. In addition to soymilk and other
dairy alternatives, categories that have done particularly well include tofu,
energy bars, meal replacements, and meat alternatives. Categories on the
rise include soy-based snacks, chips, soynuts, edamame (fresh green soy-
beans), and soy-enriched pasta, breads, and cereals.
The overall soyfoods industry has grown dramatically since the mid-1990s,
from $1.2 billion in 1996 to an estimated $4.0 billion in 2004 (see Table 1.3).
Though the industry is beginning to show signs of maturity and growth has
slowed, soyfood sales are still outpacing the growth in the grocery market
as a whole, with prepared convenience foods, snacks, and dairy and meat
alternatives growing quickly. In the near future, the U.S. market can expect
to see a wide assortment of new products, including snack foods, chips,
cultured products, and a new generation of meat products that closely resem-
ble muscle meat.
Soybean Nutritional Components
In comparison to many of today’s major food sources, soybeans are truly a
nutritional superpower. They contain the highest amount of protein of any
grain or legume; substantial amounts of fat, carbohydrates, dietary fiber,
vitamins, and minerals; and a veritable pharmacy of phytochemicals useful
TABLE 1.3
U.S. Soyfoods Market (1996 to 2005)
Year
$
(Millions)
Growth Rate
(%)
1996 1244 11.5
1997 1484 19.3
1998 1747 17.8
1999 2288 31.0
2000 2769 21.0
2001 3234 16.8
2002 3648 12.8
2003 3912 7.2
2004 3996 2.1
2005 (projected) 4218 3.0
Source: Soyfoods: The U.S. Market 2005, Soyat-
ech, Inc./SPINS, Inc., Bar Harbor, ME, 2005.
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- 7. Boca Raton LondonNew York A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc. in Food Soy Applications Mian N. Riaz, Ph.D.
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- 9. Preface Soyfood utilization aroundthe world varies widely. Asia utilizes soybeans primarily as traditional foods such as tofu, soymilk, and fermented products, whereas Western nations consume more soybeans in the form of refined soy protein ingredients used in food processing than as tofu or soymilk. The consumption in Asia is based on longstanding traditional eating habits and food production methods. In Western nations, the consumption of soybeans as direct human food is a somewhat new phenomenon, although it is gaining increased acceptance and significance. Soybeans in food applications became very popular after the Food and Drug Administration approved a soy protein health claim in 1999. The use of soy in various food applications is of major importance to food industries. Because soy ingredients are being applied in so many diverse food systems, they are increasingly being regarded as ver- satile ingredients. Not only are soybean ingredients healthy, but they also play a major role in food functionality. Currently, a limited amount of information is available on the use of soybeans in food applications, even though many types of soy ingredients can be used in various food systems. Sometimes it is difficult to decide what types of soy ingredients and processing will be best for certain food appli- cations. This book provides insights into the different types of soy ingredi- ents and their processing requirements for food applications. It serves as a source of information to all who are involved with the production of foods containing soy ingredients. For readers new to this area, the book can further their understanding of soy ingredients and their many applications. This book summarizes some of the fundamentals to be considered when applying soy ingredients to food systems. The text is an excellent starting point for research and development personnel, students, and food technol- ogists and other professionals in the food processing field. It brings together in-depth knowledge of processing food with soy ingredients and practical experience in the application of soy in food. It offers a wealth of information about the health benefits of soy protein, the current soyfood market, and the processing of soybeans into different soy ingredients. Also discussed is the use of soy protein in baked goods, pasta, cereal, meat products, and food bars. Some of the material addresses how to process soybeans into soy milk, soy beverages, and texturized soy protein; how to select identity-preserved soybeans for various food applications; how to overcome the beany flavor of some of the soy products; and how soy protein is fulfilling the need for protein in underdeveloped countries. This book is a valuable resource for information on the technical and practical applications of soy ingredients and will be a useful guide for selecting the proper soy ingredients for various 2981_C000.fm Page iii Thursday, September 29, 2005 8:40 AM
- 10. applications. Most ofthe contributors to this book have at least 10 to 15 years of practical experience in their respective fields. The editor owes a large debt of gratitude to the many individuals who have provided information and inspiration. 2981_C000.fm Page iv Thursday, September 29, 2005 8:40 AM
- 11. The Editor Mian N.Riaz, Ph.D., earned his bachelors and masters degrees in food technology from the University of Agriculture, Faisalabad, Pakistan, and his doctorate from the University of Maine, Orono. He is currently Head of the Extrusion Technology Program at the Food Protein Research and Develop- ment Center and a graduate faculty member in the Food Science and Tech- nology Program at Texas A&M University, College Station. Dr. Riaz conducts research on extruded snacks, texturized vegetable protein, pet food, aqua- culture feed, oilseed processing, and extrusion-expelling of oilseeds. He is also the editor of the book Extruders in Food Applications (Technomic) and co-author of the book Halal Food Production (CRC Press). 2981_C000.fm Page v Thursday, September 29, 2005 8:40 AM
- 12. 2981_C000.fm Page viThursday, September 29, 2005 8:40 AM
- 13. The Contributors B. Bater TheSolae Company LLC St. Louis, Missouri M. Hikmet Boyacioglu Food Engineering Department Istanbul Technical University Istanbul, Turkey H. Chu The Solae Company LLC St. Louis, Missouri Lynn Clarkson Clarkson Grain Company, Inc. Cerro Gordo, Illinois Ignace Debruyne Ignace Debruyne & Associates Izegem, Belgium Peter Golbitz Soyatech, Inc. Bar Harbor, Maine Jim Hershey American Soybean Association/ World Initiative for Soy in Human Health (WISHH) Program St. Louis, Missouri Xiaolin L. Huang The Solae Company LLC St. Louis, Missouri Joe Jordan Soyatech, Inc. Bar Harbor, Maine Rongrong Li Givaudan Flavors Corporation Cincinnati, Ohio Frank A. Manthey Department of Plant Sciences North Dakota State University Fargo, North Dakota M.K. McMindes The Solae Company LLC St. Louis, Missouri Mark Messina Loma Linda University Loma Linda, California I.N. Mueller The Solae Company LLC St. Louis, Missouri A.L. Orcutt Astaris LLC St. Louis, Missouri M.W. Orcutt The Solae Company LLC St. Louis, Missouri Paul V. Paulsen The Solae Company LLC St. Louis, Missouri Mian N. Riaz Extrusion Technology Program Texas A&M University College Station, Texas 2981_C000.fm Page vii Thursday, September 29, 2005 8:40 AM
- 14. Brad Strahm The XIMGroup LLC Sabetha, Kansas Steven A. Taillie The Solae Company LLC St. Louis, Missouri Wesley Twombly Nuvex Ingredients, Inc. Blue Earth, Minnesota David Welsby The Solae Company LLC St. Louis, Missouri 2981_C000.fm Page viii Thursday, September 29, 2005 8:40 AM
- 15. Contents 1. Soyfoods: Marketand Products .................................................... 1 Peter Golbitz and Joe Jordan 2. Overview of the Health Effects of Soyfoods ............................ 23 Mark Messina 3. Processing of Soybeans into Ingredients................................... 39 Mian N. Riaz 4. Soy Ingredients in Baking........................................................... 63 M. Hikmet Boyacioglu 5. Developing and Producing Protein-Enhanced Snacks and Cereals ....................................................................... 83 Brad Strahm 6. Soy in Pasta and Noodles ............................................................ 93 Wesley Twombly and Frank A. Manthey 7. Soy Base Extract: Soymilk and Dairy Alternatives .................111 Ignace Debruyne 8. Meat Alternatives........................................................................ 135 Brad Strahm 9. Textured Soy Protein Utilization in Meat and Meat Analog Products ........................................................ 155 M.W. Orcutt, M.K. McMindes, H. Chu, I.N. Mueller, B. Bater, and A.L. Orcutt 10. Food Bars ..................................................................................... 185 Steven A. Taillie 11. Ready-to-Drink Soy Protein Nutritional Beverages............... 199 Paul V. Paulsen, David Welsby, and Xiaolin L. Huang 2981_C000.fm Page ix Thursday, September 29, 2005 8:40 AM
- 16. 12. Soy ProductOff-Flavor Generating, Masking, and Flavor Creating................................................... 227 Rongrong Li 13. Selecting Soybeans for Food Applications.............................. 249 Lynn Clarkson 14. World Initiative for Soy in Human Health ............................. 267 Jim Hershey Index ..................................................................................................... 275 2981_C000.fm Page x Thursday, September 29, 2005 8:40 AM
- 17. 1 1 Soyfoods: Market andProducts Peter Golbitz and Joe Jordan CONTENTS History of Soyfoods ................................................................................................2 Growth and Development in the Western World........................................2 Soybean Industry Blossoms in the United States.........................................3 Soybeans Grow Around the World............................................................... 3 Soybean Production and Utilization for Food....................................................4 Soyfoods in Asia................................................................................................5 Soyfoods in Europe...........................................................................................6 Soyfoods in Africa.............................................................................................6 Soyfoods in the United States..........................................................................7 Development of the U.S. Soyfoods Industry...........................................7 The Americanization of Soyfoods ............................................................8 Soybean Nutritional Components........................................................................9 Soy Protein ...................................................................................................... 10 Soy Oil.............................................................................................................. 10 Carbohydrates and Fiber .............................................................................. 10 Vitamins and Minerals...................................................................................11 Isoflavones .......................................................................................................12 Soyfoods and Protein Ingredients ......................................................................12 Whole Dry Soybeans ......................................................................................12 Tofu ...................................................................................................................13 Soymilk.............................................................................................................14 Tempeh.............................................................................................................15 Soymilk Yogurt................................................................................................15 Miso...................................................................................................................15 Soy Sauce..........................................................................................................16 Okara.................................................................................................................16 Natto .................................................................................................................16 Soynuts .............................................................................................................17 Meat Alternatives............................................................................................17 2981_C001.fm Page 1 Wednesday, September 28, 2005 2:14 PM
- 18. 2 Soy Applicationsin Food Cheese Alternatives ........................................................................................17 Nondairy Frozen Desserts .............................................................................18 Green Vegetable Soybeans (Edamame).......................................................18 Soy Sprouts ......................................................................................................18 Full-Fat Soy Flour............................................................................................18 Defatted Soy Flour ..........................................................................................19 Textured Soy Flour .........................................................................................19 Soy Protein Concentrate.................................................................................19 Soy Protein Isolate ..........................................................................................20 Conclusion .............................................................................................................20 It can be eaten raw, roasted, fermented, or cultured. It can be a small, green bean or a magically transformed concoction that closely resembles ham- burger, ice cream, bacon, or even a fully dressed turkey. Yes, the soybean is one of the most nutritious and versatile foods on the planet, and it is an important food platform for the 21st century. History of Soyfoods Even though soy is a new food for many in Western society, the Chinese have considered it an important source of nutrition for almost 5000 years. The first reference to soybeans, in a list of Chinese plants, dates back to 2853 B.C., and ancient writings repeatedly refer to it as one of the five sacred grains essential to Chinese civilization. The use of the soybean in food spread throughout the Asian continent during the early part of the last millennium, as people in each region developed their own unique soyfoods based on tradition, climate, and local taste preferences. Natto, for instance, is a product consisting of fermented soybeans that was developed at least 3000 years ago in Japan and continues to be popular in some regions of that country today. Growth and Development in the Western World When European missionaries and traders traveled to Asia during the 1600s and 1700s, they wrote in their journals about traditional soyfoods, such as tofu and soymilk, that they had encountered in the cultures they explored. Then, in the late 1700s, both Benjamin Franklin and a curious world traveler named Samuel Bowen sent soybean samples to the United States for culti- vation. Mr. Bowen’s soybean crops, grown in Georgia, were even used to manufacture soy sauce and a soy-based vermicelli substitute. But, it was not until Asians began to emigrate to Europe and North America during the 1800s that soyfoods were consistently made by and for people in the United States. Several Chinese tofu and soymilk shops were established in cities 2981_C001.fm Page 2 Wednesday, September 28, 2005 2:14 PM
- 19. Soyfoods: Market andProducts 3 with large Asian populations in Europe and on the East and West coasts of the United States; however, throughout the 19th century, soyfoods tended to be made in small, family-run shops and were distributed and consumed primarily in Asian neighborhoods. During the 1920s, a number of smaller companies with ties to the Seventh-Day Adventist Church (many members of which are vegetarian) began making tofu in the states of Tennessee and California. During that same time, soy flour started to gain favor in both Europe and the United States as a low-cost source of protein in the produc- tion of meat substitutes, and, during both World Wars, large amounts of soy flour were used to help offset meat shortages. Soybean Industry Blossoms in the United States Large-scale development of the soybean crop and processing industry began in the United States during the 1940s and 1950s, spurred on by a rapid increase in domestic and worldwide demand for both protein meal and vegetable oil. Harvested soybean acreage in the United States more than tripled between 1940 and 1955, from 4.8 million acres to 18.6 million, while total production of soybeans increased nearly fivefold, from 78 million bush- els to 374 million. As the number of acres devoted to soybeans continued to grow during the 1960s, the United States became a world soybean super- power and began exporting large quantities of soybeans, as well as the basic crush products of meal and oil, to Europe and Asia. By 1970, U.S. farmers had planted an incredible 43 million acres of soybeans and produced 1.1 billion bushels. The crop would more than double in size to 2.3 billion bushels, or 62.5 million metric tons, by 1979. Industry growth has slowed in recent years due to increased competition from other producing nations, but the United States still produces roughly 75 million metric tons of soybeans each year. Soybeans Grow Around the World Though still the largest soybean exporting country in early 2005, the United States has lost the dominant position it once had in the global soy trade. Brazil, Argentina, and India have all become major producers as the world’s demand for soy as food, vegetable oil, and animal feed has continued to increase. Given the amount of available arable land and water resources in Brazil, along with its low labor costs, it is expected that Brazil will eventually become the number one soybean-producing nation. Already, South America as a continent produces more soybeans that North America (combined U.S. and Canadian production). Growth in China, where this story began, has been plagued with inefficiencies and lags behind most major producing countries, although it is still the fourth largest soybean grower. In 2004, it was the world’s largest importer of soybeans as well. 2981_C001.fm Page 3 Wednesday, September 28, 2005 2:14 PM
- 20. 4 Soy Applicationsin Food Soybean Production and Utilization for Food For the marketing year 2004/05, the world produced approximately 229 million metric tons of soybeans, enough to give each man, woman, and child 35 kg of soybeans each, or the equivalent of nearly 300 L of soymilk for a year (see Table 1.1). But, the world’s soybeans are not used exclusively for humans. Each year, on average, an estimated 85% of the world’s soybeans are processed (crushed) into soybean meal (used primarily for animal feed) and vegetable oil. Approximately 10% is used directly for human food and the balance is used for seed or on-farm feeding of animals or is waste material. In addition to the 10% of the crop that is used directly for human food — for products such as tofu, soymilk, natto, and miso — an estimated 4 to 5% of the soybean meal that is produced from soybean crushing is further processed into soy protein ingredients that, in turn, are further pro- cessed into various meat and food products or are used in infant formula, dairy and meat alternatives, nutritional supplements, and energy bars. Soyfood consumption patterns around the world vary widely, with such regions as Asia utilizing soybeans primarily in such traditional foods such as tofu, soymilk, and fermented products. In Western nations, more soybeans are consumed in the form of refined soy protein ingredients (used in food processing) than in the production of tofu and soymilk. As well, Soyatech, Inc. (Bar Harbor, ME) estimates that Asian nations utilize 95% of the soybeans consumed directly as human food in the world today. The heavy consumption in Asia is based on long-standing traditional eating patterns and food pro- duction methods. In Western nations, consumption of soybeans as direct human food is a somewhat new phenomenon, although it is gaining increased acceptance and significance. As can be seen in Table 1.2, Asian countries consume far more soybeans and soy protein equivalent per day than do Western nations. For example, TABLE 1.1 World Soybean Production by Major Producers Production (million metric tons) 2000/01 2001/02 2002/03 2003/04 2004/05 United States 75.06 78.67 75.01 66.78 85.48 Brazil 39.50 43.50 52.00 52.60 63.00 Argentina 27.80 30.00 35.50 34.00 39.00 China 15.40 15.41 16.51 15.40 18.00 India 5.25 5.40 4.00 6.80 6.50 Paraguay 3.50 3.55 4.50 4.00 5.00 All others 9.42 8.60 9.60 10.23 11.64 Total 175.93 185.12 197.12 189.81 228.63 Source: U.S. Department of Agriculture estimates, March 2005. 2981_C001.fm Page 4 Wednesday, September 28, 2005 2:14 PM
- 21. Soyfoods: Market andProducts 5 in Taiwan, per capita consumption is estimated to be as high as 19.15 kg per year, and in Japan at 7.73 kg per year. In the United States, yearly per capita consumption of soybean is just 0.33 kg per year; however, world average per capita consumption is approximately 2.4 kg per year, equivalent to around 6.5 g of soybeans per day, or an estimated 2.4 g of soy protein per person per year. Soyfoods in Asia Throughout Asia, the soybean is used in a wide variety of traditional and modern food products. For example, in Japan, tofu is the most popular soy- food consumed, eaten at virtually all meals in one form or another, from silken tofu in miso soup for breakfast to plain or fried tofu for lunch or dinner. Also, tofu is used in dessert products and as an ingredient in cutlets and other TABLE 1.2 Annual Per Capita Consumption (2001) of Soybeans for Direct Food Soybeans Soy Protein Equivalent (36% Protein) (g/day) Rank Country (kg/yr) (g/day) 1 Taiwana 19.15 52.46 18.89 2 Korea (North) 10.67 29.24 10.53 3 Korea (South) 8.79 24.07 8.67 4 Libya 8.68 23.78 8.56 5 Japan 7.73 21.19 7.63 6 China 7.31 20.03 7.21 7 Indonesia 7.16 19.61 7.06 8 Uganda 4.71 12.91 4.65 9 Nigeria 2.76 7.57 2.72 10 Thailand 2.34 6.40 2.30 11 Myanmar 1.91 5.22 1.88 12 Yemen 1.85 5.06 1.82 13 Costa Rica 1.40 3.84 1.38 14 Peru 1.40 3.83 1.38 15 Vietnam 1.27 3.48 1.25 16 Canada 0.68 1.88 0.68 17 Zimbabwe 0.65 1.77 0.64 18 Philippines 0.51 1.39 0.50 19 India 0.41 1.13 0.41 20 Ethiopia 0.38 1.04 0.38 21 United Statesa 0.33 0.89 0.32 22 Germany 0.24 0.66 0.24 23 Egypt 0.24 0.66 0.24 24 South Africa 0.23 0.64 0.23 25 Congo, Democratic Republic 0.18 0.50 0.18 World average 2.39 6.54 2.36 a Soyatech, Inc., estimates. Source: Food and Agriculture Organization (FAO) food balance sheets. 2981_C001.fm Page 5 Wednesday, September 28, 2005 2:14 PM
- 22. 6 Soy Applicationsin Food prepared foods. Soymilk, after a quick rise and fall in sales in the mid-1980s, is making a strong comeback in Japan due to increased interest in functional foods and beverages and recognition of the powerful nutritive qualities of the soybean. Natto, a fermented soyfood product, has historically been extremely popular in Japan and is consumed daily by many people. Natto is prized for its unique taste and form, as well as its powerful blood-thinning and cleansing qualities. Miso, another fermented soyfood, is consumed daily by many Japanese in soup broth, salad dressings, and food toppings. In China, tofu is also very popular, as is fermented tofu, yuba (dried soymilk skin), soymilk, and a variety of regional specialties, including soy noodles. In addition, soy powder mixes and isolated soy proteins are becoming popular as food ingredients and in consumer-oriented mixes for health. In Taiwan, the art of meat substitutes and alternatives has reached new heights with meat-, chicken-, and fish-like products made from soy proteins, yuba, gluten, and tofu. In Indonesia, tempeh is the most popular soyfood and is sold at thou- sands of food stands and kiosks throughout the country. It is made fresh each day by many individuals who purchase inoculated soybeans the night before and by morning have fresh tempeh to sell as street vendors. Throughout Asia, in addition to tofu and other regional soyfoods, processed and packaged soymilk has grown increasingly important in recent years and has become big business in Hong Kong, Korea, Malaysia, Singapore, Thailand, and Vietnam. Soyfoods in Europe European consumption of soyfoods is similar to that of the United States, with meat and dairy alternatives comprising most of the soyfood sales. Soymilk and meat alternatives sales are particularly strong in the United Kingdom, which has a relatively large vegetarian population. Wide accep- tance of soymilk can also be found in Belgium, where the continent’s largest soymilk producer is located. Throughout the rest of Europe, tofu is known, but it is not as popular as meat and dairy alternatives. As in the United States, soyfoods have become more of a mainstream food item, having crossed over from the natural products market to being widely available now in mainstream supermarkets. Soyfoods in Africa While a pan-African consumer market for soyfoods has yet to develop, certain countries in Africa have readily adopted soyfoods due to their high protein level and nutritional quality. Some of the use is a result of food aid programs where soybean products such as textured soy flour or soy- bean–corn meal are distributed, while in some countries feeding programs for workers and school children take advantage of the relatively low cost and high nutritive value of the soybean. In South Africa, a modern soyfoods market has developed; fresh and aseptically packaged soymilk is available, 2981_C001.fm Page 6 Wednesday, September 28, 2005 2:14 PM
- 23. Soyfoods: Market andProducts 7 as well as a wide array of products made from textured soy flour and sold as soy “mince,” a low-cost ground meat replacement. Soyfoods in the United States In the United States, perhaps one of the more interesting markets for soy products has developed due to a number of supportive micro and macro trends, as well as a strong history of “Americanization” of foreign and ethnic foods. This is due to the United States being a large, immigrant melting pot that blends many different foods and eating traditions. In addition, a strong entrepreneurial spirit exists among both immigrants and those who are moti- vated by a desire to create livelihoods that benefit not only themselves but also the world at large. Soyfoods, due to their high nutritional value and their low environmental impact when compared to meat and dairy production, have become a rising star in the U.S. food marketplace. Development of the U.S. Soyfoods Industry The modern soyfoods industry in the United States has developed in three distinct phases. The first phase, one of discovery, took place during the 1920s, when early proponents of vegetarian diets such as Dr. John Harvey Kellogg of Battle Creek, MI, became interested in the healthful properties of the soybean. In addition to studying the usefulness of soybeans in the diets of diabetics, he also developed and marketed North America’s first meat and dairy analogs made from the soybean. During those early years, soyfoods were promoted primarily among members of the largely vegetarian Seventh- Day Adventist Church and other special interest groups. The second phase was distinctly industrial and paralleled the industrial- ization of American society. As mentioned earlier, soy flour had become an important component in food production during the Second World War, as meat shortages developed due to the increased protein and food needs of the armed forces and the disruption of farm commerce during the war years. Unfortunately, soy flour and protein processing was not a well-developed science at that time, and, as a result, most of the products had distinctive off-flavors and were tolerated at best, but not appreciated. The image of soybean-based foods became that of an inferior substitute and extender, to be used in times of crisis and shortage, rather than that of a nutritional alternative to meat and dairy foods for everyday use. In the 1950s and 1960s and during the meat shortages of the 1970s in the United States, numerous food companies and meat processors used textured soy proteins to extend meat products. These early attempts were met with resistance by consumers who complained of poor flavor, texture, and color. Following this period, many food processors found it necessary to reassure consumers that their products contained no fillers or cereal additives. As this industrial phase ended, soybean-based foods were neither highly respected nor desired by American consumers. 2981_C001.fm Page 7 Wednesday, September 28, 2005 2:14 PM
- 24. 8 Soy Applicationsin Food It was during the 1970s that a third phase for soy emerged, a new age. In both the United States and Europe, a large, young counterculture had devel- oped that began to question traditional American and Eurocentric values based on industrialization, military interventionism, and the politics of a meat-centered diet. New Age thinkers popularized the concepts of going back to the land, pacifism, vegetarianism, and the more equitable distribu- tion of food resources. Two important publications of that era were Diet for a Small Planet, in which Frances Moore Lappé wrote of the misallocation of food resources and the value of the soybean, and the Book of Tofu, in which William Shurtleff and his wife Akiko Aoyagi wrote of, and eloquently illus- trated, the beauty and tradition of soyfoods. The rediscovery of the value that the soybean could have in a modern world helped to inspire a new soyfoods movement in both the United States and Europe. During this time, hundreds of small companies were founded that were dedicated to produc- ing soyfoods and educating the public about their use. The desire for a “right livelihood” within these companies and among their customers inspired tremendous innovation and helped to build a natural food and products industry and market. According to statistics gathered by Soyatech, Inc., over 2000 new soyfood products were introduced during the 1980s in the United States, and many of them were made by small companies that made primarily (or exclusively) soy-based foods. Products such as tofu, tempeh, miso, tofu hot dogs, veggie burgers, tofu ice cream, soymilk, and other dairy alternatives all became common fixtures in natural food stores. As the young counterculture that founded this movement began forming households of their own, these soy- foods progressively crossed over into mainstream supermarkets. The Americanization of Soyfoods The pace of innovation and new product development accelerated through- out the 1990s with the continued Americanization of soyfoods into products that were more familiar and convenient, as well as healthful. In particular, the 1996 decision by White Wave, Inc. (Boulder, CO), to market its soymilk in traditional “gable-top” milk cartons in the refrigerated food cases of supermarkets led to a dramatic shift in soymilk consumption. Until that point, most soymilk was sold in natural foods stores and was packaged in aseptic packaging. Primarily vegetarians, the lactose-intolerant, and people who had ethical or religious objections to drinking cow’s milk consumed it. Later, however, when White Wave positioned its Silk® brand soymilk to taste and look more like dairy milk, sales of soymilks in the United States exploded from $124 million in 1996 to nearly $700 million in 2004. Soymilk became simply another, perhaps more healthful, choice in the dairy case. Another, broader impetus to the popularity of soyfoods was a 1999 deci- sion by the U.S. Food and Drug Administration (FDA) to allow food man- ufacturers to include a claim for heart health on foods that contained more than 6.25 g of soy protein per serving (if they were also low in fat). This 2981_C001.fm Page 8 Wednesday, September 28, 2005 2:14 PM
- 25. Soyfoods: Market andProducts 9 health claim states, “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of food] provides [amount] grams of soy protein.” Since then, the range of foods that include soy protein has been limited only by the imag- ination of food scientists and marketers. In addition to soymilk and other dairy alternatives, categories that have done particularly well include tofu, energy bars, meal replacements, and meat alternatives. Categories on the rise include soy-based snacks, chips, soynuts, edamame (fresh green soy- beans), and soy-enriched pasta, breads, and cereals. The overall soyfoods industry has grown dramatically since the mid-1990s, from $1.2 billion in 1996 to an estimated $4.0 billion in 2004 (see Table 1.3). Though the industry is beginning to show signs of maturity and growth has slowed, soyfood sales are still outpacing the growth in the grocery market as a whole, with prepared convenience foods, snacks, and dairy and meat alternatives growing quickly. In the near future, the U.S. market can expect to see a wide assortment of new products, including snack foods, chips, cultured products, and a new generation of meat products that closely resem- ble muscle meat. Soybean Nutritional Components In comparison to many of today’s major food sources, soybeans are truly a nutritional superpower. They contain the highest amount of protein of any grain or legume; substantial amounts of fat, carbohydrates, dietary fiber, vitamins, and minerals; and a veritable pharmacy of phytochemicals useful TABLE 1.3 U.S. Soyfoods Market (1996 to 2005) Year $ (Millions) Growth Rate (%) 1996 1244 11.5 1997 1484 19.3 1998 1747 17.8 1999 2288 31.0 2000 2769 21.0 2001 3234 16.8 2002 3648 12.8 2003 3912 7.2 2004 3996 2.1 2005 (projected) 4218 3.0 Source: Soyfoods: The U.S. Market 2005, Soyat- ech, Inc./SPINS, Inc., Bar Harbor, ME, 2005. 2981_C001.fm Page 9 Wednesday, September 28, 2005 2:14 PM
- 26. 10 Soy Applicationsin Food for the prevention and treatment of many chronic diseases. Soybeans vary widely in nutrient content based on the specific variety and growing condi- tions, but typically they contain 35 to 40% protein, 15 to 20% fat, 30% car- bohydrates, 10 to 13% moisture, and around 5% minerals and ash. Soy Protein The protein in the soybean contains all eight amino acids essential for human health, but until recently it was accepted that soy protein was lower in quality than many animal proteins. These earlier assumptions were based on an older method of evaluating protein quality, the protein efficiency ratio (PER), which is based on the growth rates of rats as measured in laboratory tests. However, rats require 50% more methionine (one of the amino acids found in soybeans) than humans do, making this particular method inappropriate for evaluating soy protein quality for human consumption. In order to make up for the shortcomings of the PER evaluations, the World Health Organi- zation of the United Nations and the U.S. Food and Drug Administration have adopted a new method for evaluating protein quality called the protein digestibility corrected amino acid score (PDCAAS). This method uses an amino acid score, a comparison between the amino acid pattern of a protein and human amino acid requirements, and a factor for digestibility to arrive at a value for the quality of a protein. Using the new PDCAAS method, soy protein products generally receive scores of between 0.95 and 1.00, the high- est value possible. Soy Oil Soybeans, in comparison to other beans, grains, and cereals, contain a high amount of fat, but, as we have come to learn, all fats are not created equal. Many of our major health problems today are due to the fact that people eat too much fat, and the fat being consumed is unhealthful and of poor quality. Fortunately, the fat found naturally in the soybean — and, by extension, in most traditionally processed soyfoods such as tofu, soymilk, tempeh, full- fat soy flour, and liquid soybean oil — can be categorized as a healthful fat. Approximately 50% of the fat in soybeans is linoleic acid, an essential poly- unsaturated fat that can help lower cholesterol by bringing down blood lipid levels. In addition, soybean oil can contain as much as 8% alpha-linolenic acid, which is an omega-3 fatty acid (the healthful fat commonly derived from fish) and which is believed to be beneficial in lowering the risk of heart disease. Carbohydrates and Fiber Soybeans contain an interesting mix of both soluble and insoluble carbohy- drates (including dietary fiber) that together constitute about 30% of the 2981_C001.fm Page 10 Wednesday, September 28, 2005 2:14 PM
- 27. Soyfoods: Market andProducts 11 soybean. The primary soluble carbohydrates in the soybean are sugars: stachyose, raffinose, and sucrose. Collectively, they make up about 10% of the soybean, although the amounts of these sugars vary according to the variety of soybean and its growing conditions. Raffinose and stachyose, the primary oligosaccharides (complex sugars) in soy, are significant because they are not digested or used as nutrients directly by the human body, but they are used as nutrients by the Bifida bacteria in the lower intestine. These types of intestinal flora are considered important for human health. It is believed that their presence can reduce the incidence of colon cancer and other intestinal disorders; however, when the bacteria break down these sugars, intestinal gas is created as a byproduct, creating discomfort and flatulence in some people. This can create a barrier to soybean consumption (especially in Western culture), but some Japanese companies are actually isolating and marketing these sugars as health supplements and food ingre- dients. The insoluble carbohydrates, or dietary fiber, come primarily from the outer hull and structural cell walls of the soybean and are composed of cellulose, hemicellulose, and pectin. This component contributes to the over- all healthfulness of the soybean, because consumption of adequate amounts of dietary fiber has been shown to reduce the risk of heart disease and cancer, as well help to improve bowel function. Vitamins and Minerals In addition to providing high-quality protein, fat, and carbohydrates, soy- beans are also rich in vitamins, minerals, and a number of other valuable phytochemicals. The major mineral components of soybeans are potassium, sodium, calcium, magnesium, sulfur, and phosphorus. Mineral content can vary widely due to both the type of soil and growing conditions for the soybean. Although soybeans are not considered to be very rich sources of any one particular vitamin, they do contribute to overall nutritional well- being. The water-soluble vitamins in soybeans are thiamine, riboflavin, nia- cin, pantothenic acid, biotin, folic acid, inositol, and choline. An integral part of lecithin, choline has been linked to the health of cellular walls and the nervous system. In 2001, the FDA formally recognized the healthful prop- erties of choline by agreeing to allow food manufacturers to add a choline health claim to product labels. Fat-soluble vitamins present in the soybean are vitamins A and E. Vitamin A exists as provitamin beta-carotene and is present in higher levels in the immature, green vegetable soybean than in the mature (dry) soybean. Tocopherols, the most widely available, naturally occurring vitamin E compound, fill two major roles as a component of soy oil. First, vitamin E is an important element of human nutrition, although its bioactive properties have been scrutinized in recent years, and many of the health claims about vitamin E remain unproven. Second, tocopherols are antioxidants, which means that they are chemicals that prevent a substance from reacting with oxygen. Their presence in soybean oil slows down the degradation of the oil. 2981_C001.fm Page 11 Wednesday, September 28, 2005 2:14 PM
- 28. 12 Soy Applicationsin Food Isoflavones It should come as no surprise that plants contain powerful chemicals that can have a profound effect on an individual’s health or well-being. Many of the drugs used in Western medicine today originate from plant sources. Traditional medicines, such as those used by some Asian cultures, herbalists, and homeopaths, are centered on plant remedies. The term phytochemical is used to describe a class of plant-based chemical compounds that have an effect on the human or animal organism. The soybean is a virtual pharmacy of beneficial phytochemicals for human health and disease regulation; how- ever, over the past few years, one particular set of compounds has gained the most attention and become the focus of hundreds of studies and numer- ous world conferences — isoflavones. For all practical purposes, no other food contains as significant an amount of these chemicals as does the soy- bean. Generally speaking, minimally processed soyfoods, including full-fat soy flour, tofu, and soymilk, have the highest levels of isoflavones. Isofla- vones are also considered phytoestrogens, or plant estrogens, because they have a similar chemical make-up and effect on the human body as estrogen; however, the estrogenic effects of soy isoflavones are much (perhaps as much as 10,000 times) weaker than the human estrogen hormone. The major isoflavones in soybeans are genistein, daidzein, and glycitein. Genistein has shown some promise in preventing and treating prostate and breast cancers. Although glycitein comprises only 5 to 10% of soy isoflavones, recent stud- ies suggest that it may have far higher estrogenicity and bioavailability than either genistein or daidzein. Soyfoods and Protein Ingredients As indicated earlier, approximately 10% of the world’s soybean crop is used directly for human food, and a stunning array of products is made from the humble bean. Many of the following soy-based foods utilize the whole soybean, while some are made with a variety of soy protein ingredients, including isolated soy protein, soy protein concentrate, and soy flour. Whole Dry Soybeans Whole dry soybeans are, of course, the original soyfood. Dried in the pod while still in the field, whole soybeans contain approximately 37% protein, 17% fat, 10% dietary fiber, 20% carbohydrates, 5% ash (total minerals), and 11% moisture. Composition varies among the many different varieties of soybeans. Some seeds are larger in size and higher in protein than others, while some varieties have a brown, buff, or clear-colored hilum (the spot on the soybean where it connects to the pod). Dried, yellow soybeans are the 2981_C001.fm Page 12 Wednesday, September 28, 2005 2:14 PM
- 29. Soyfoods: Market andProducts 13 most commonly available type. Soyfood processors carefully select the proper varieties of soybean for the type of products they are making. For example, soymilk and tofu manufacturers prefer large, high-protein soy- beans with clear hilums so their finished product yields are high, exhibit a mild flavor profile, and are light in color. Most identity-preserved food-grade varieties are sold at a premium to food processors. Dried soybeans will last over a year but must be kept cool and dry, as they begin to degrade when stored at too high a temperature or in moist conditions. Tofu Tofu is perhaps the most widely consumed soyfood in the world today. It is a regular part of the diet in many Asian nations. Tofu is widely available across the United States and in most other Western nations. This soft, white, almost cheese-like product is favored for its versatility, mild flavor, and high nutritional value. It is naturally processed and, as a result, retains a good deal of the important nutrients and phytochemicals of the soybean, such as the isoflavones. Tofu is especially valuable due to its chameleon-like quality of being able to take on the flavor of whatever spices and ingredients are used with its preparation. For example, in the same sitting, one could dine on a fresh green salad served with a creamy tofu dill dressing, eat a healthy serving of marinated barbecued tofu, and finish with a tofu chocolate cream pie. When tofu is made, soaked whole soybeans are ground to produce a slurry, which is added to water and boiled. After cooking, the pulp is removed from the mixture, leaving soymilk. While the soymilk is still hot, a natural mineral coagulant — such as calcium sulfate or magnesium chloride, or a mixture of both — is slowly added to the hot liquid. Within minutes, the soymilk begins to curdle and large white clouds of tofu curd begin to form in a sea of yellow whey. After 15 minutes or so, the curds are removed from the whey and placed under pressure in cloth-lined forming boxes. The curds are then pressed to form soft, regular, firm, or extra-firm tofu. The size of the curd and length of pressing time determine the style of tofu produced. The softer the tofu, the lower the protein and fat levels and the higher the water content. Soft tofu is also usually smoother in texture than firm tofu. Firm tofu, on the other hand, is higher in protein and fat and lower in moisture and has a denser, chewier texture. Silken tofu — the soft, smooth variety commonly sold in an aseptic pack- age — is made in a slightly different manner. To make silken tofu, either calcium sulfate or glucono-delta-lactone is added to a thicker, richer soymilk, and the mixture is put into a package. This package, with the soymilk and coagulant mixture, is heated to the proper temperature to activate the coag- ulation, and the soymilk is transformed into one solid, smooth curd, right in the package. Typically, tofu contains between 10 and 15% protein and 5 to 9% fat. It is relatively low in carbohydrates and in fiber (because the pulp was removed), 2981_C001.fm Page 13 Wednesday, September 28, 2005 2:14 PM
- 30. 14 Soy Applicationsin Food making it easy to digest. Tofu made with calcium sulfate or calcium chloride contains higher levels of calcium than those made with other coagulants and is therefore sometimes sought after by those seeking to supplement their current calcium intake. One 4-oz. serving of calcium-coagulated tofu can contain as much bioavailable calcium as one 8-oz. serving of cow’s milk. Tofu is commonly found packed in sealed, water-filled tubs, but it is also available in vacuum or aseptic packaging. Unless it is aseptically packaged, tofu requires refrigeration at or under 40°F. Tofu can also be frozen for longer storage, although it will tend to have a much different texture when thawed, becoming crumbly and more chewy. Regular, pressed tofu is best when fried, baked, grilled, or barbecued; used as a meat alternative; or added to stir fry dishes. In most cases, the best way to prepare tofu for use is to first drain the tofu on paper or cloth towels to reduce the water content. This improves the ability of the tofu to absorb flavors, reduces the amount of water that has to be removed in the cooking stage, and firms up the tofu, making it easier to handle. Silken tofu is best used in soups or blended into vegetable spread, sauces, cream substitutes, pie fillings, puddings, or desserts. Some firm varieties of silken tofu are available, as well, and these can be used as pressed tofu in many recipes. The Japanese favor silken tofu and usually eat it prepared very simply. For example, it may be served fresh, with just a little soy sauce and scallions, or in miso soup. Silken tofu, because it is soft and lacks the cohesiveness of pressed tofu, is more difficult to handle. Many new tofu products on the market today have been flavored and then baked, fried, or smoked prior to sale. These new tofu products are “recipe ready” and easier to use for many consumers, especially those with a limited amount of time to cook or those who are unfamiliar with tofu. Soymilk Traditionally, soymilk is the liquid extract of the soybean, which can be used in the preparation of tofu or as a nutritious beverage, but the beverage- quality soymilks available today are usually prepared in a slightly different fashion, utilizing a number of more modern food processing techniques in order to produce a blander product with greater appeal to Western tastes. As with tofu, soymilk generally contains most of the active phytochemicals present in soybeans, including high amounts of isoflavones. Some soymilks are made with isolated soy protein as a base. Many are fortified with vitamins and minerals (such as vitamins A and D and calcium) to bolster their position as a viable alternative to cow’s milk. Soymilk can be used as a direct, one- to-one replacement for cow’s milk in most food formulations and recipes. Soymilk works very well in baking recipes and is an excellent cream soup or sauce base. It can be put on cereal or made into yogurt, pudding, or ice cream. A variety of powdered soymilk products can be mixed with water at low ratios if one needs a very thick, cream-like soymilk base. 2981_C001.fm Page 14 Wednesday, September 28, 2005 2:14 PM
- 31. Soyfoods: Market andProducts 15 Tempeh Tempeh is a traditional, fermented soyfood that is unique in its texture, flavor, and versatility. Originally from Indonesia, tempeh has a flavor that is distinctively different from other soyfoods, sometimes described as “nutty” or “mushroom like.” It is made from the whole soybean, which has been dehulled, cracked, and cooked in water with added vinegar to reduce the pH. Once cooked, the soybean is mixed with the spores of the Rhizopus oligosporus fungus and left to incubate for 24 hours at 88°F. At the end of this period, the tempeh is a compact, cake-like product that is completely covered with, and penetrated by, white mold mycelia. Tempeh may also be made with other grains or seeds mixed in during processing to vary the taste and texture of the final product. Tempeh contains about 19% protein, is higher in fiber than tofu, and is a significant source of vitamins and minerals. Tempeh is available fresh or frozen and is sold in plain and flavored varieties. It can be found in natural food stores and in the produce section of many supermarkets. Tempeh should be used within a few weeks of purchase but can be frozen for longer storage. It can be marinated prior to use, works very well in stir-fry dishes, and can be baked, grilled, or deep fat fried. Tempeh can also be grated and formed into patties or balls. Soymilk Yogurt Soymilk yogurt is made in the same manner as cow’s milk yogurt. Pasteur- ized soymilk is inoculated with Acidophilus, Bifida, or other suitable cultures and incubated until the culture has turned the soymilk into yogurt. It tastes very similar to cow’s milk yogurt, is available in a variety of styles and flavors, and is generally sold in 6- to 8-oz. and quart containers. It is very high in protein and a great source of isoflavones. These products may not be labeled as “yogurt” in the United States, as they are not made with cow’s milk, but manufacturers package them in familiar yogurt containers and refer to them as “cultured soy” or “cultured soymilk.” Miso Miso is a rich and flavorful paste made from either fermented and aged whole soybeans or soybeans in combination with wheat, barley, or rice. This salty paste is a treasured soup base and flavoring ingredient used throughout Japan, Korea, Taiwan, Indonesia, and China. Many types of miso are available in the world today, from sweet white miso, which is quite mild, to dark savory miso, which is much more robust and salty. Miso has some unique medicinal properties and is believed to help reduce the effects of radiation and other environmental poisons on the body. It contains enzymes and bacteria that can aid in digestion. It is high in protein, but it also contains high levels of sodium and should be consumed sparingly. To produce miso, whole cooked 2981_C001.fm Page 15 Wednesday, September 28, 2005 2:14 PM
- 32. 16 Soy Applicationsin Food soybeans are mixed together with koji nuggets — grain such as wheat, rice, or barley that has been cultured with a fungal starter (Aspergillus oryzae) — and fermented under very specific conditions for the type of miso being made. When the mash is fully ripened, it is blended and packaged for sale. Usually the longer the miso has aged, the more complex the flavor. Most of the miso sold today is pasteurized and refrigerated. Miso is sold in natural food stores and in many supermarkets along with other Asian foods. It has a long shelf life when refrigerated. Due to its distinctive fermented flavor, it can be added to recipes or blended with tofu to add a cheese-like note. Soy Sauce Soy sauce is the most well known and popular of the traditional soyfoods and is used extensively as a flavoring ingredient in most Asian cooking. When naturally processed, soy sauce is produced in a manner similar to that of miso. When made exclusively with soybeans, the product is called tamari. If it is processed with a fermented wheat starter, the product is called shoyu. Much of the soy sauce sold today is not naturally fermented. Instead, it is made with hydrolyzed vegetable protein (HVP), sugar, color, and preserva- tives. HVP is produced from soy protein using chemically induced fermen- tation. All soy sauces are high in sodium and should be used sparingly. Some reduced-sodium varieties are available on the market today, as well as a number of flavored soy sauce products. From a nutritional prospective, tamari contains the highest protein level of the soy sauces, followed by shoyu and then HVP-based soy sauce; however, the high amount of sodium in all of these products should preclude anyone from using soy sauce as a nutri- tional food. Naturally processed soy sauce is available in natural food stores; both the naturally fermented and HVP forms are sold in most supermarkets. Due to its high salt content, soy sauce has a long shelf life without refriger- ation but will keep longer when stored at cooler temperatures. Okara Okara is the fibrous remains of the soybean after it has been processed to make soymilk. It is very high in moisture and contains the insoluble carbo- hydrates and dietary fiber of the soybean, as well some remaining protein and fat. When fully cooked, it has a bland flavor and makes an excellent addition to breads and other baked goods. It can also be used to make meat alternatives or processed into tempeh. It is not usually sold in stores, as it is very wet, heavy, and highly perishable. Natto Natto is a whole soybean product, popular in Japan, that is produced by fermenting small, cooked soybeans with Bacillus natto until they develop a 2981_C001.fm Page 16 Wednesday, September 28, 2005 2:14 PM
- 33. Soyfoods: Market andProducts 17 sticky, viscous coating. Natto is made from a number of specific varieties of soybeans and has a distinct taste and aroma that are an acquired taste for most. It is available only in Japanese food stores and is mostly imported, as very little is produced in the United States. It can be found frozen or fresh and will last about a week when refrigerated. Soynuts Soynuts are roasted soybeans that have been prepared by the dry or oil roasting of whole or split soybeans that have first been soaked in water. They can be sold with a coating of salt or other flavoring ingredients. Soynut pieces can be blended with other nuts and used in baking applications and other food preparations. Soynuts are high in protein, fiber, and the isoflavones found naturally in whole soybeans. Soynut butter is a paste of ground soynuts that is prepared in a manner similar to that of peanut butter and may have salt, sweeteners, and additional oil added. Soynuts and soynut butter can be found in many natural food stores and in some supermarkets. Meat Alternatives This is a broad product category, as literally hundreds of products are made from tofu, tempeh, textured soy flour, textured soy concentrate, isolated soy protein, and wheat gluten. Products take the shape of burgers, hot dogs, sausages, luncheon meats, chicken, fish, and ground meat. Most products are made with a combination of vegetable protein ingredients to achieve the best texture and are flavored for a particular use. Most are low in fat, and many are completely fat free. Meat alternatives are sold fresh and frozen and can be purchased in natural food stores, supermarkets, and, increasingly, in res- taurants. Recent innovations include improved flavor and texture, as well as a new generation of extruded products that resemble muscle meat. Cheese Alternatives A wide range of cheese alternatives is made from soymilk, tofu, and other vegetable protein ingredients. These products can be found flavored to taste like American, mozzarella, cheddar, Monterey Jack, parmesan, and other cheeses. Most of these processed cheese products are made with a combination of soy and casein protein (from cow’s milk). Casein is used because it is the protein responsible for the melting action common in cheese when it is heated. Without added casein, soy cheese alternatives would soften when heated but not melt or stretch. It also adds a flavor note that is associated with cheese. Some soy-based cheese alternatives have either had the fat replaced with vegetable oil or completely removed. These products are usually lactose and cholesterol free, as well. Soy cheese alternatives are also used as an ingredient in prepared frozen pizzas, stuffed in pasta, and added to frozen entrees. 2981_C001.fm Page 17 Wednesday, September 28, 2005 2:14 PM
- 34. 18 Soy Applicationsin Food Nondairy Frozen Desserts This product category was one of the first to prove to Americans that products made from tofu and soybeans could taste good. Popularized by products such as Tofutti® brand (Tofutti Brands, Inc., Cranford, NJ) frozen desserts in the mid-1980s, this category has seen a recent reemergence due to the increased popularity of soymilk and premium dessert products. Nondairy frozen des- serts are essentially ice cream products that are made using soymilk, tofu, or soy protein in place of dairy milk or cream. Both hard-pack and soft-serve styles exist, as well as novelty ice cream pops and sandwiches. Green Vegetable Soybeans (Edamame) This simple and nutritious soyfood is really just the whole soybean picked at its peak of maturity, at a time when it is high in sucrose and chlorophyll. It is harvested in the pod and is sold either in the pod or shucked, after being blanched and frozen. Because they are picked when their sugar levels are high, green vegetable soybeans are very sweet and pleasant tasting, and they have a firm texture. The common and traditional Japanese names for the green vege- table soybean are edamame when it is sold in the pod and mukimame when it is sold as individual beans. Green vegetable soybeans contain about 13% protein (the same amount as tofu) and are naturally high in calcium. They work very well in stir-fry dishes and can also be blended into dips and other preparations. They are becoming increasingly easy to find in the United States, as some American food processors are now packaging them for the domestic market. Soy Sprouts Soy sprouts are the fresh, crisp sprouts of germinated soybeans. They are a traditional food of Korea and may be eaten raw or in prepared food dishes. They are usually harvested after having grown for 5 to 7 days. They contain vitamin C and are high in protein and fiber. Soy sprouts are slightly larger than ordinary bean sprouts, which are prepared from mung bean seeds. Soy sprouts are available in some specialty food stores. Full-Fat Soy Flour Full-fat soy flour is made from whole or dehulled soybeans, which are ground into fine flour. Because it is made from the whole soybean, the composition of full-fat flour is identical to that of the natural soybean, with a protein content between 35 and 40% and a fat level between 15 and 20%. It is extremely nutritious and high in fiber and contains all of the vitamins, minerals, and phytochemicals of soybeans. Full-fat soy flour is available either as raw, enzyme-active flour or as toasted flour. The raw form is great for baking, as the active enzyme, lipoxygenase, helps to bleach wheat flour and produce a whiter bread loaf with improved moisture retention and shelf 2981_C001.fm Page 18 Wednesday, September 28, 2005 2:14 PM
- 35. Soyfoods: Market andProducts 19 life. The toasted variety has a somewhat nuttier flavor and tends to have a slightly darker color. Enzyme-active full-fat soy flour can also be used to make fresh soymilk, which eliminates the need to soak or grind soybeans. Defatted Soy Flour Defatted soy flour, sometimes referred to simply as soy flour, is made by finely grinding defatted soybean flakes. The defatted flakes are produced by first crushing soybeans in a roller mill and then using a solvent to remove the oil. Any remaining solvent is then removed from the flake by heat and evaporation. Because the fat is thus removed, defatted soy flour has a higher protein content than full-fat soy flour. It contains 44 to 54% protein, 0.5 to 1.0% fat, 17 to 18% dietary fiber, and 30 to 35% total carbohydrates. (Defatted soy grits are processed from the same material but are not as finely ground.) Low-fat soy flours can also be produced using soybeans that have been mechanically pressed to remove the oil from soybeans. Because mechanical extraction of the oil is not as efficient as solvent extraction, these flours almost always contain some remaining fat, usually between 7 and 10%, and their protein content ranges from 45 to 50%. Defatted soy flour contains a higher level of isoflavones than either whole soybeans or products produced from them, due to the increased concentration of protein. Some of the nutrients attached to the oil — such as the vitamin E and lecithin — have been removed, but most of the vitamins, minerals, fiber, and phytochemicals have been retained. Textured Soy Flour Textured soy flour is probably the most popular form of defatted soy flour available to consumers. It is produced from defatted soy flour that is hydrated and then cooked under high pressure in an extruder to produce a variety of textured and shaped products. The extrusion process produces the unique texture by expanding the structure of the soy protein. A die at the end of the extruder determines the shape and size of the piece or granule. Flavor or color can be added to the soy flour prior to processing. Available in a range of colors, shapes, and sizes, textured soy flour, or textured soy protein (also known as TVP®, a registered trademark of the Archer Daniels Midland Com- pany), is most commonly used as a meat extender or replacement due to its meat-like appearance and consistency when prepared for use. To use textured soy flour, one must first hydrate the granules with hot or boiling water. As the textured soy flour absorbs the water, it expands and softens. Soy Protein Concentrate Soy protein concentrate is comprised of between 65 and 70% soy protein, with trace amounts of fat and 5 to 6% fiber. It is made by processing defatted 2981_C001.fm Page 19 Wednesday, September 28, 2005 2:14 PM
- 36. 20 Soy Applicationsin Food soybean flakes in either an alcohol or water bath to remove soluble sugars. The result is a concentrated form of soy flour with improved flavor and functional characteristics. It can be texturized (the most common form found in meat alternatives) or spray dried to form a powder used in infant formulas and other dairy alternative applications. Due to the alcohol-washing step used to reduce the sugars, most of the isoflavones are removed during processing, although the quality of the protein is not reduced. It is also more easily digested than soy flour as most of the sugars responsible for creating flatulence are removed in the processing. Soy Protein Isolate Soy protein isolate, or isolated soy protein, is 85 to 90% pure soybean protein, processed from the same defatted soy flakes as defatted soy flour and soy protein concentrate, but isolated soy proteins are processed one step beyond concentrates to remove not only the fat and soluble sugars but also the insoluble sugars and dietary fiber. Isolated soy proteins are very low in flavor, highly digestible, and easy to use in food, beverage, and baking formulations. They disperse easily in water and work well as emulsifiers, helping to bind water and fat together. Isolated soy proteins are found in many of the meat and dairy alternatives on the market today. They are also used in conjunction with whole soybeans to make certain types of tofu, are blended with tofu in tofu hot dogs to improve the texture, are used in some soymilk products in place of the whole soybean, and are used in nondairy creamers and infant formulas. They are also found in many of the weight- and muscle-building products sold to the fitness market. Due to their highly functional qualities, the meat industry uses isolated soy proteins to help bind water and fat in processed meats and to reduce shrinkage during cooking. Consumers can buy isolated soy proteins under a variety of names and labels, marketed as a nutritional aid or a base ingredient for food and bev- erages. They are most likely to be found in natural food or supplement stores and can be purchased through some direct mail catalogs. Properly stored, they should have a long shelf life with or without refrigeration. Conclusion One would be hard pressed to find a more valuable resource for our planet’s food supply than the humble soybean. With its healthfulness proven by its widespread use for thousands of years and its ample supply and low cost, the soybean is proving itself to be a food for all humankind. For the next few decades, it is likely that we will see continual improvements in plant genetics and processing technology that will make the soybean an even more 2981_C001.fm Page 20 Wednesday, September 28, 2005 2:14 PM
- 37. Soyfoods: Market andProducts 21 valuable resource for food, feed, and a myriad of innovative industrial uses as well. Given its long history and tremendous versatility, the soybean is indeed proving itself to be a new food platform for the 21st century. 2981_C001.fm Page 21 Wednesday, September 28, 2005 2:14 PM
- 38. 2981_C001.fm Page 22Wednesday, September 28, 2005 2:14 PM
- 39. 23 2 Overview of theHealth Effects of Soyfoods Mark Messina CONTENTS Introduction ...........................................................................................................23 Soybean Isoflavone Content and Profile ...........................................................24 Isoflavone Absorption and Metabolism ............................................................26 Asian Soy Protein and Isoflavone Intake...........................................................27 Soy and the Risk of Chronic Diseases................................................................27 Cancer...............................................................................................................27 Breast Cancer .............................................................................................28 Prostate Cancer..........................................................................................29 Osteoporosis ....................................................................................................30 Coronary Heart Disease.................................................................................30 Hot Flashes.......................................................................................................32 Intake Recommendations for Healthy Adults..................................................32 Safety Concerns.....................................................................................................33 Conclusions............................................................................................................33 References ..............................................................................................................34 Introduction Foods made from the soybean have been consumed for centuries in Asia and by vegetarians in non-Asian countries for decades. The soybean has long been embraced as a source of high-quality protein from which a wide variety of foods can be made. The quality of soy protein is now recognized as being essentially equivalent to that of animal protein, and for this reason, in the year 2000, the U.S. Department of Agriculture (USDA) issued a ruling allowing soy protein to completely replace animal protein in the National School Lunch Program; previously, soy protein could replace no more than 30% of animal protein.1 2981_C002.fm Page 23 Wednesday, September 28, 2005 12:38 PM
- 40. 24 Soy Applicationsin Food During the past 15 years, the popularity of both traditional and Western- style soy products has increased dramatically in the United States. This popularity has little to do with the protein quality of the soybean; rather, it is because of research suggesting that the consumption of fairly modest amounts of soyfoods is associated with health benefits in a variety of areas. In fact, in 1999, the U.S. Food and Drug Administration approved a health claim for the cholesterol-lowering effects of soy protein.2 Beyond heart dis- ease, proposed benefits include reductions in the risk of breast and prostate cancer3 and osteoporosis.4 More speculative data suggest soyfoods may also favorably affect kidney function5 and cognitive function6 and help to allevi- ate hot flashes in menopausal women.7 In addition to an assortment of vitamins and minerals, like all plant foods the soybean contains numerous biologically active nonnutritive substances.8 Certainly, it is reasonable to think that collectively these components (nutri- ents and nonnutrients) account for the hypothesized health benefits of soyfoods; however, much evidence suggests that one particular class of compounds — isoflavones — is primarily responsible for many of these benefits, although the protein is required for cholesterol reduction. Isoflavones are classified as phytoestrogens because they bind to estrogen receptors,9 but they are very complex molecules that not only differ from estrogen but also have potentially important nonhormonal properties as well.10 Furthermore, in comparison to estrogen receptor alpha, isoflavones preferentially bind to9 and activate estrogen receptor beta (ERβ).11,12 The pref- erential binding of isoflavones to ERβ likely contributes to evidence suggest- ing that isoflavones function as selective estrogen receptor modulators.13 The “estrogen-like” qualities of isoflavones have caused them to be viewed as possible alternatives to conventional hormonal therapy, and for this reason many women experiencing menopause have been attracted to soyfoods. Isoflavones are present in many different plants, but the soybean is the only commonly consumed food to contain nutritionally relevant amounts of these diphenolic molecules. Consumer interest in isoflavones has led to the devel- opment of isoflavone supplements and the use of isoflavones as food forti- ficants. The purpose of this review is to evaluate the strength of the evidence for the different proposed benefits of soy and to make intake recommendations on the basis of this information. Due to space limitations only cancer, osteoporosis, coronary heart disease, and hot flashes are discussed. Soybean Isoflavone Content and Profile Isoflavones are a subclass of flavonoids that have a very limited distribution in nature and are found in few commonly consumed foods, which accounts for surveys showing that among typical non-Asians isoflavone intake is 2981_C002.fm Page 24 Wednesday, September 28, 2005 12:38 PM
- 41. Overview of theHealth Effects of Soyfoods 25 negligible. The 15-carbon (C6–C3–C6) backbone of flavonoids can be arranged as a 1,3-diphenylpropane skeleton (flavonoids nucleus) or as a 1,2-diphenyl- propane nucleus skeleton (isoflavonoid nucleus). In isoflavones, the B-ring is attached to the C-ring at the 3- rather than the 2-position (Figure 2.1). The three soybean isoflavones are genistein (4′,5,7-trihydroxyisoflavone), daidzein (4′,7-dihydroxyisoflavone), and glycitein (7,4′-dihydroxy-6-methoxyisofla- vone). Typically, more genistein exists in soybeans and soyfoods than daid- zein, whereas glycitein comprises less than 10% of the total isoflavone content of the soybean.14 Isoflavone supplements made from the hypocotyledon (often referred to as soy germ) portion of the soybean are rich in glycitein and low in genistein. In contrast, isoflavone supplements derived from soy molasses have an isoflavone profile similar to that found in the soybean. Soybeans contain approximately 1.2 to 3.3 mg isoflavones per g dry weight, and every gram of protein in traditional soyfoods is associated with approximately 3.5 mg isoflavones; however, processing can dramatically reduce isoflavone content, especially in the case of alcohol-extracted soy protein concentrate and isolate (Table 2.1). Consequently, it is difficult to predict the isoflavone content of soy protein without knowing the process used to the make the specific product. For example, isolated soy proteins have an isoflavone content that ranges from 0.5 to 2.0 mg/g. In conjunction with Iowa State University, the USDA has created an online database of the isoflavone content of foods (http://www.nal.usda.gov/fnic/foodcomp/ Data/isoflav/isoflav.html). Isoflavones are naturally present in the soybean primarily in their beta glycoside form (genistein, daidzein, and glycitein). The sugar molecule is attached at the 7-position of the A ring. An acetyl or malonyl group can be FIGURE 2.1 Structures of the three aglycone soybean isoflavones. O HO O R1 R2 OH 7 5 1 A C B 2 4 H OCH3 H H OH H R2 R1 Genistein Daidzein Glycitein 2981_C002.fm Page 25 Wednesday, September 28, 2005 12:38 PM
- 42. 26 Soy Applicationsin Food attached to the glucose molecule, resulting in a total of 12 different soybean isoflavones isoforms. Heating does not cause a significant loss of isoflavones, although it can result in decarboxylation, thereby converting the malonyl isoflavone glycosides into acetyl glycosides. Perhaps more relevant from a physiological perspective because of the possible impact on bioavailability (see next section) is the conversion (primarily as a result of bacterial hydrol- ysis during fermentation) of the glycosides into aglycone isoflavones. Finally, because the weight of the aglycone isoflavone, the biologically active isomer, is only approximately 60% that of the glycoside, unless spe- cifically indicated 100 mg isoflavones can refer to between 60 and 100 mg of active molecule. To avoid confusion, the recommendation has been made to use the aglycone weight.15 This is the case in the text that follows. Isoflavone Absorption and Metabolism Isoflavone glycosides are not absorbed intact, but hydrolysis (from the acid pH of the stomach, endogenous enzymes, and intestinal microflora) does readily occur in vivo; thus, there is little difference in bioavailability between the glycoside and aglycone forms of isoflavones.16 After the ingestion of soyfoods, a small peak in serum levels occurs approximately 1 to 2 hours later, but the major serum peak occurs 4 to 6 hours after ingestion. Most work TABLE 2.1 Isoflavone (Aglycone Weight) Content of Selected Foods Food (Nutrient Database Number) Samples Isoflavone Content (mg/100 g edible portion) Mean Minimum Maximum Tofu Firm (16126) 6 24.7 7.9 34.6 Regular (16427) 4 23.6 5.1 33.7 Silken, firm (16162) 2 27.9 23.8 32.0 Natto (16113) 5 58.9 46.4 87.0 Soymilk (16120) 14 9.7 1.3 21.1 Miso (16112) 7 42.6 22.70 89.2 Tempeh (16114) 6 43.5 6.9 62.5 Soynuts, dry roasted (16111) 7 128.4 1.66 201.9 Soybeans, cooked (16109) 1 54.7 NA NA Isolated soy protein (16122) 14 97.43 46.5 199.3 Soy protein concentrate (aqueous washed) (99060) 3 102.1 61.2 167.0 Soy protein concentrate (alcohol washed) (16121) 5 12.5 2.1 31.8 Source: U.S. Department of Agriculture, Washington, D.C. (http://www.nal.usda.gov/ fnic/foodcomp/index.html). 2981_C002.fm Page 26 Wednesday, September 28, 2005 12:38 PM
- 43. Overview of theHealth Effects of Soyfoods 27 estimates that the half-life of isoflavones is between 4 and 8 hours; 24 hours after the consumption of soyfoods nearly all of the isoflavones are excreted.16 Serum isoflavone levels increase in a dose-dependent fashion in response to soyfood consumption.17,18 The highest sustained serum isoflavone levels are likely achieved by dividing daily isoflavone intake into several doses. This method of ingestion reflects the pattern of isoflavone intake from soyfoods in Asia. A huge variation in isoflavone metabolism exists among individuals. This variation leads to very different serum levels of both isoflavones and their metabolites in response to the ingestion of isoflavones.19 This variation likely contributes to the inconsistency noted in the literature regarding the health effects of isoflavones. An especially potentially important observation is that only approximately 30 to 50% of subjects possess the intestinal bacteria that convert the isoflavone daidzein into the isoflavonoid equol, which has been proposed as an especially beneficial compound.20 Asian Soy Protein and Isoflavone Intake Part of the enthusiasm for the health benefits of soy, rightly or wrongly, is based on the low rates of breast and prostate cancer21 and coronary heart disease (CHD)22 in Asia, particularly Japan. Thus, arguably, one basis for determining Western soy intake recommendations is Asian soy consump- tion. Although widely varying estimates of Asian soy intake have been reported in the literature within the past 7 years, many large surveys of soy protein and isoflavone consumption by Asian adults have been published. These surveys, which often include as many as nine different questions related to soy, provide a very accurate picture of actual intake in Asia. It is clear from these data that early soy intake estimates were greatly exagger- ated. Surveys suggest that older (50 years) Japanese adults typically consume 7 to 11 g soy protein and 30 to 50 mg isoflavones per day. Intake in Hong Kong and Singapore is lower than in Japan, and significant regional intake differences exist for China. Evidence suggests ≤10% of the Asian population consumes as much as 25 g soy protein or 100 mg isoflavones per day. Soy and the Risk of Chronic Diseases Cancer The National Cancer Institute in the United States has been actively investi- gating the anticancer effects of soy since 1991, when the first request for applications on this subject was issued.8 In part, this interest in soy stems 2981_C002.fm Page 27 Wednesday, September 28, 2005 12:38 PM
- 44. 28 Soy Applicationsin Food from the historically low incidence rates of breast and prostate cancer in Asia.21 Evidence suggests that the potential anticancer effects of soy extend beyond these two cancers, but, because most research has focused only on breast and prostate cancer, these are the cancers discussed in this chapter. Several putative anticarcinogens can be found in soybeans and soyfoods;8 however, the soybean isoflavones have received the most attention.10 With regard to both cancer prevention and treatment, the effects of genistein on signal transduction are of particular interest.10 Genistein inhibits the growth of a wide range of cancer cells in vitro by inhibiting the activity of certain enzymes, inducing apoptosis, and inhibiting the activation of NF-κB and Akt signaling pathways;10 however, the possible antiestrogenic effects of isofla- vones — which were first demonstrated in rodents almost 40 years ago — provide an additional possible mechanism for the hypothesized anticancer effects of soy.23 Breast Cancer The relationship between soy intake and breast cancer risk has been inves- tigated extensively. Animal studies generally suggest that soy is protective against this cancer; however, the epidemiologic data are only weakly or not at all supportive of this hypothesis.24 Furthermore, clinical studies investi- gating markers of breast cancer risk, such as breast tissue density and serum estrogen levels, have also produced relatively unimpressive results.25,26 Thus, overall, it is difficult to conclude that adult soy intake reduces breast cancer risk; however, provocative data suggest that intake during adolescence reduces breast cancer risk later in life. Two research groups from the United States — Larmatiniere and col- leagues from the University of Alabama and Hilakivi-Clarke and colleagues from Georgetown University in Washington, D.C. — are responsible for all of the animal work examining the effects of early genistein exposure on mammary carcinogenesis. Both teams conducted their research in Spra- gue–Dawley rats, and each used the indirect acting carcinogen 7,12-dime- thylbenz(a)anthracene to initiate mammary tumors. These studies show that exposing rats to genistein during the first three weeks of life reduces tumor multiplicity by approximately one half (Table 2.2).27,28 Interestingly, Lamartiniere et al. have shown that, although genistein administration dur- ing adulthood has little impact on tumor development, when it is given to rats also exposed to genistein when they were young, tumor number is suppressed significantly beyond that achieved with early intake alone (Table 2.2). Only two epidemiologic studies have examined the “early soy” hypothe- sis, but both studies are consistent with the animal data. A large (1459 cases and 1556 controls) Chinese case-control study found that soy protein con- sumption during adolescence reduced adult breast cancer risk by approxi- mately 50%, but adult soy consumption had no impact.29 In this study, the intake cutoff of the fourth quartile was only 11.19 g/d soy protein. Also in 2981_C002.fm Page 28 Wednesday, September 28, 2005 12:38 PM
- 45. Overview of theHealth Effects of Soyfoods 29 support of this hypothesis is a U.S. study (501 cases and 594 controls) involv- ing Asian– Americans that found high soy consumption throughout life was associated with a one third reduction in risk of breast cancer, whereas high adult intake alone was not protective.30 Prostate Cancer In 2000, the International Prostate Health Council suggested that isoflavones prevent latent prostate cancer from progressing to the more advanced form of this disease.31 Recent animal work supports this conclusion.32 Overall, with few exceptions, animal studies show that isoflavones and isoflavone- rich soy protein inhibit prostate tumors induced by chemical carcinogens or via the implantation of prostate cancer cells.3 Interestingly, isoflavones in combination with tea extracts were shown to reduce tumor growth in mice implanted with androgen-sensitive prostate cancer cells more effectively than either agent alone.33 Both soyfoods and tea are important components of the Asian diet. Very limited epidemiologic investigation of the relationship between soy intake and prostate cancer risk has been conducted, although the data are generally supportive of the hypothesis that soy is protective. A recent anal- ysis of ten epidemiologic studies found that soy intake was associated with a one third reduction in prostate cancer risk.34 However, the limitations of the epidemiologic data in terms of both quantity and quality should not be overlooked. Many of the epidemiologic studies did not comprehensively evaluate soyfood intake, although a recent Japanese case-control study that did found that, when comparing the highest with the lowest soyfood intake, quartile risk was reduced by nearly 50%.35 The mechanism by which soy may reduce prostate cancer risk has not been identified, but soy does not appear to lower serum testosterone lev- els,36,37 although in mice equol was recently shown to bind to and inactivate TABLE 2.2 Effect of Genistein on Development of 7,12-Dimethylbenz(a)anthracene- Induced Mammary Tumors in Rats Exposure Period Tumors/Rat None 8.9 Prenatal (in utero) 8.8 Adult (PND 100–180) 8.2 Prepubertal (PND 1–21) 4.3 Prepubertal and adult 2.8 Note: Nursing dams and adults were fed diets containing 250 mg genistein per kg. PND, postnatal day. Source: Lamartiniere, C.A. et al., J. Women’s Cancer, 2, 11–19, 2000. With permission. 2981_C002.fm Page 29 Wednesday, September 28, 2005 12:38 PM
- 46. 30 Soy Applicationsin Food dihydrotestosterone, the active metabolite of testosterone within the pros- tate.38 Finally, in several studies neither soy nor isoflavones were found to lower prostate-specific antigen (PSA) levels — a marker of prostate cancer risk — in healthy subjects,39,40 although several very preliminary studies have found that soy or isoflavones may favorably affect PSA levels in prostate cancer patients.41,42 Osteoporosis The first human study suggesting that isoflavones favorably affect bone health was published in 1998.43 Since then, at least 14 additional publications have examined the effects of soyfoods, isoflavone-rich soy protein, or isolated isoflavones on bone loss in perimenopausal (N-1) or postmenopausal (N-14) women.4 As reviewed by Messina et al.,4 these trials were conducted in 9 countries, included from 10 to 75 subjects per group (although most involved more than 30), and, with one exception, were conducted for less than 1 year. The results from these studies are mixed but overall indicate that isoflavones reduce bone loss; however, the relatively small size and the short duration of these osteoporosis trials prevent drawing definitive conclusions. To best predict likely long-term effects, trials should be conducted for 2 to 3 years.44 The disappointing results from a 3-year trial involving the synthetic isofla- vone ipriflavone are certainly evidence of this.45 Nevertheless, the results from these isoflavone trials are sufficiently encouraging to recommend that women concerned about their bone health consider using isoflavones to help ward off osteoporosis although they should not be used as a substitute for estab- lished antiosteoporotic medications. This conclusion is consistent with the Asian epidemiologic data, which generally show that among Asian women higher soy/isoflavone intake is associated with higher bone mineral density.4 Little dose–response information is available, but most trials examining the skeletal system have used approximately 80 mg total isoflavones per day. The means by which bone loss is reduced has not been identified, but evidence suggests both hormonal and nonhormonal mechanisms. Large, long-term trials of isoflavones and bone health are underway. Coronary Heart Disease The cholesterol-lowering effects of soy protein were first demonstrated in humans in 1967.46 Ten years later, a landmark paper by Italian researchers on the hypocholesterolemic effects of soy protein was published in the jour- nal Lancet.47 Despite these reports, however, and others published over the next 15 years, it was not until 1995 that soy received widespread attention.48 That year, Anderson and colleagues published a metaanalysis in the New England Journal of Medicine which summarized the existing data on soy and cholesterol.48 They found that soy protein lowered cholesterol in 34 of the 38 trials and that the average decrease in low-density lipoprotein cholesterol (LDLC) levels was an impressive 12.9%. The metaanalysis also found soy 2981_C002.fm Page 30 Wednesday, September 28, 2005 12:38 PM
- 47. Overview of theHealth Effects of Soyfoods 31 protein modestly raised high-density lipoprotein cholesterol, a finding that has been confirmed by other research.49 The metaanalysis comprised the bulk of the research on which the FDA based its approval for a health claim for soy protein 4 years later (the 14 clinical studies with the best experimental designs were given the highest priority50), although it is now generally recognized that the initial estimates of the potency of soy protein were exaggerated. In 2003, a metaanalysis by Weggemans and Trautwein51 that included 10 clinical trials and involved nearly 1000 subjects published after 1995 found that the average reduction in LDLC in response to soy protein was only 4%. These more modest effects are still clinically relevant, however. Some estimates suggest that each 1% reduction in cholesterol reduces CHD risk by as much as 3 to 4%.52,53 Fur- thermore, soy protein can be combined with other dietary approaches to effectively lower cholesterol.54 Also, the use of soy protein along with a statin might help to avoid doubling the dose of medication when the target cho- lesterol goal is not achieved with the medication alone, thereby reducing the possibility of adverse drug effects. When the FDA approved the soy protein health claim, they established 25 g/day as the threshold intake level necessary for cholesterol reduction. The consumption of this amount of soy protein represents a significant dietary challenge for non-Asians, as this figure is approximately 2.5 times the typical Japanese intake. The FDA set 25 g/day as the required intake not because evidence suggested that lower amounts were not efficacious but because few trials used amounts lower than this. In fact, provocative evidence indicates that fewer than 25 g/day is hypocholesterolemic.55 A far more contentious issue is the extent, if any, to which isoflavones impact the cholesterol-lowering effects of soy protein (isoflavones by them- selves do not lower cholesterol). The position of the FDA is that the evidence does not warrant concluding that isoflavones play a role in cholesterol reduc- tion, although a recent metaanalysis suggests otherwise.56 A leading hypoth- esis for the hypocholesterolemic effects of soy is that the peptides resulting from the ingestion of soy protein upregulate hepatic LDLC receptors.57,58 Importantly, the role of soy in reducing CHD risk may extend far beyond cholesterol reduction. In fact, it may be that the possible coronary benefits of isoflavones exceed those of soy protein, although this remains speculative. Several studies have found that isoflavones enhance endothelial function59 and systemic arterial compliance,60 both of which are considered to be indi- cators of coronary health.61,62 In addition, isoflavones and their metabolites are antioxidants,63 and speculative data suggest that isoflavone-rich soy pro- tein inhibits LDL-oxidation64,65 and perhaps platelet aggregation.66 Indirect support for the coronary benefits of isoflavones comes from several Asian epidemiologic studies that found soyfood intake to be strongly inversely related to the risk of coronary events; the reduction in risk was far beyond that which could be attributable to cholesterol reduction alone.67–70 It is clear that the many possible coronary benefits warrant adding soyfoods to a heart- healthy diet. 2981_C002.fm Page 31 Wednesday, September 28, 2005 12:38 PM
- 48. 32 Soy Applicationsin Food Hot Flashes For the majority of women, hot flashes begin prior to menopause, and about 10 to 15% of women who have hot flashes have them very frequently and severely.71 Both clinical7 and epidemiologic72 data suggest that isoflavones help to alleviate hot flashes. The percentage of women in Asian countries, especially Japan, who experience hot flashes is quite low relative to the West.73 In 2003, Messina and Hughes7 published a review of 19 trials that involved over 1700 women and examined the effects of soyfoods or isofla- vone supplements on menopausal symptoms. After excluding six trials from their regression analysis for methodological reasons, they found among the remaining 13 trials a statistically significant relationship between initial hot flash frequency and treatment efficacy. According to these findings much of the inconsistency in results from the clinical trials can be attributed to the variation in mean initial hot flash frequency among the studies. No dose– response information from the trials in this analysis is available, but the isoflavone doses used in the clinical trials range from 34 to 100 mg/day. In contrast to this analysis, however, Krebs et al.74 found no support for the ability of isoflavones (from both red clover and soybeans) to alleviate hot flashes. Their analysis included 25 trials involving 2348 participants who had a mean daily hot flash frequency of 7.1. Thus, at this point it is not possible to conclude that isoflavones are helpful for alleviating hot flashes, but, arguably, the data are sufficiently suggestive for health professionals to suggest that women try isoflavones for relief. This recommendation is par- tially justified because of the possible coronary and skeletal benefits of isofla- vones, as discussed previously. Intake Recommendations for Healthy Adults The only soy intake recommendation from an established health organiza- tion comes from the FDA, which recommends a soy protein intake of 25 g/ day for cholesterol reduction. This recommendation should not form the basis for soy intake among the general population, however, because it pertains to only one health attribute of soy and is unrelated to isoflavone intake.50 If soy contributes to the lower breast and prostate cancer incidence in Asia, then the average daily Japanese intakes of 30 to 50 mg isoflavones may be efficacious, but the mean intake may significantly underestimate the amount needed for maximum protection. The epidemiologic studies dem- onstrating reductions in the risk of coronary heart disease and cancer involved comparisons across intake categories, and the largest reductions in risk are typically associated with intakes greater than the mean. Thus, max- imum protection might require the consumption of closer to 75 mg/day of isoflavones. This higher value is similar to the level of isoflavones used in 2981_C002.fm Page 32 Wednesday, September 28, 2005 12:38 PM
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