Time To Learn About It

To illustrate the key benefits of the soybean it is important to describe the properties of this low cholesterol source of protein. Soy protein is high caliber. One can obtain all of the essential amino acids when consuming the recommended levels of soy protein. Just including soy into a non vegetarian diet can also be a very healthful contribution. Americans eat too much meat protein. This adversely affects our cancer rates, as excess protein is tumor promoting. Rising heart disease rates stem from saturated fats and cholesterol in meats that can also contribute to other diseases, especially osteoporosis. Other populations who consume less meat protein and include more soy protein are generally healthier in terms of certain lower disease rates and diseases of affluence particularly cancer of the breast and prostate as well as heart disease, diabetes, osteoporosis, and menopausal symptoms, to name a few.

Soy protein flours, concentrates and isolates have been shown to be versatile food ingredients, primarily due to their functional and nutritional properties, which serve to enhance the value of finished foods. Nutritional, health, safety and microbiological aspects of soy protein products when used for protein fortification in dietary supplements, infant formulas and traditional foods are all considered in this article.

Soy and Your Health

The facts are these; soy can ward off osteoporosis. It can help prevent ovarian, prostate and breast cancer. It can lower cholesterol, reducing the risk of heart disease and it can ease symptoms of menopause. Miraculously, one little soybean has the power to fight all these physical conditions, and it is finally receiving due recognition in this day and age.

There is ample evidence that soy protein products have a positive influence on health. Recent studies have considered the total diet as a basis for explaining, at least in part, the differences in mortality rates from coronary artery disease, stroke, and several types of cancer in various countries. A number of studies suggest that animal protein is more cholesterolemic and atherogenic than vegetable protein. This difference persists even in the face of high saturated fat consumption.

Soy protein products can be an excellent source of dietary fiber. Since dietary fiber seems to play a role in controlling blood cholesterol, and may have an effect in preventing colon cancer and improving glucose tolerance, studies with diets containing soy flour, soy concentrate or soy fiber merit special attention. Calorie reduction to avoid obesity is a genuine health concern in the minds of an informed populace. Soy protein products can make a significant contribution in weight reduction, mainly by providing essential high quality protein in a concentrated form for specially designed, low calorie high nutrient density meals.

Numerous dietary factors may contribute to an increased incidence of coronary heart disease. Animal fat is the most widely recognized atherogenic factor in the diet. A direct correlation has been established between saturated fatty acids, cholesterol levels, hypercholesterolemia, and the development of coronary heart disease. Until recent years, there have been few studies on proteins from vegetable sources. This is due possibly to the higher interest in the dietary fats theory of atherosclerosis. The difficulty is in selectively analyzing the role of dietary proteins, excluding such factors as fat and carbohydrate intake. Substitution of animal proteins with soy proteins in the diets of some animals and humans has been studied with interest, primarily for the impact on blood fat levels. Epidemiological data on the effects of various diets and the onset of atherosclerosis and heart disease show that vegetable protein intake has a beneficial impact on plasma cholesterol levels.

Lean Protein Lowers Cholesterol

The soybean plant, Glycine max, belongs to the legume family. It is able to utilize the nitrogen of the air through the action of bacteria on its roots. The protein content of the seed is about 40%. After the hulls and the oil are removed, the remaining defatted flake, which is the starting material for most commercial protein ingredients, has a protein content of approximately 50%. One of the newest developments in nutritionally based approaches to reduce the risk of coronary heart disease centers around soybeans, one of the oldest foods known to man. For centuries it has been a staple in the diets of many Asian cultures. Epidemiologists have credited soy with playing a role in minimizing the incidence of cardiovascular and other chronic degenerative diseases in the orient. Now, scientists in the United States, Europe and Australia have collectively accumulated a body of convincing evidence showing that soy protein has a positive, direct, measurable, and consistent impact on cardiovascular health.

While debate remains on just how soy protein works experts are convinced that a significant improvement in America's cardiovascular health can be achieved through the consumption of as little as 25 grams of soy protein a day. Soy protein consumption effectively lowers LDL cholesterol and triglyceride levels in the blood and leaves HDL cholesterol levels generally unaltered. LDL cholesterol is one of the primary risk factors associated with cardiovascular disease. It is a primary agent responsible for progressive atherosclerosis, the name given to the build up of plaque that clogs blood flow in arteries. Seventy-five percent of cardiovascular deaths stem from atherosclerosis. Coronary heart disease is the leading cause of disease and death in the United States for both men and women, accounting for more than 950,000 deaths annually at a total projected annual cost of more than $274 billion.
Soy protein has been shown to reduce serum cholesterol levels by as much as 23 to 25 percent even among patients already on low-fat, low-cholesterol diets. Research indicates that for each 1 percent that serum cholesterol is lowered, the risk of fatal and non-fatal coronary events is decreased by 2 to 4 percent. Even at lower levels of efficacy, soy protein can have a profound impact on reducing coronary heart disease.

For centuries, soybeans and soybean products have been the chief source of protein for millions of people in the Orient. The soybean is native to Eastern Asia, playing the type of nutritional role in the region that wheat does in the United States. At the same time, during this past century, there has been a quieter, less glamorous but more important history of the soybean in the making. Researchers and scientists have been painstakingly coming to understand the nutritional benefits and biochemical mechanisms of soy protein in the human diet. The cumulative understanding arising from their efforts now has the potential to reduce the heavy burden of coronary disease in the United States.

The ability of vegetable protein to reduce coronary heart disease was first proposed in 1908 as a result of a study conducted on rabbits. Unfortunately, widespread interest in the finding was eclipsed soon after by another discovery. Cholesterol was found to promote the formation of lipid deposits in arteries. Still, research on soy did not stop, and the coronary benefits of soy protein have been documented for more than 80 years now as a result of numerous studies in animals, and more recently, humans.

About 20 years ago, soy's ability to lower cholesterol in humans was first described. Subsequent studies confirmed these findings even as other researchers sought to determine soy's mechanisms of action. The medical community, however, did not come to recognize the significance of the growing number of small, seemingly unremarkable studies on soy protein's lipid lowering action until the beginning of this decade. In fact, it was while looking for explanations of soy's anti-cancer properties that researchers discovered the unsuspected accumulation of decades of promising work on soy's ability to reduce serum cholesterol.

In 1982, a project conducted in Italy and Switzerland confirmed that the dietary substitution of animal proteins with vegetable proteins is remarkably effective among out patients with hypercholesterolemia. A group of patients with plasma cholesterol mostly in excess of 300 milligrams per deciliter received a diet completely replacing animal protein with soy protein. A 20% to 22% drop in plasma cholesterol and low density lipoprotein (LDL) cholesterol occurred with the soy protein regimen. Younger patients were more responsive to the soy protein diet than older subjects, particularly post menopausal women. More recent clinical studies, in which soy protein was substituted for animal proteins in the diet, have confirmed these findings. The value of soy protein for producing significant reduction in total serum cholesterol, LDL cholesterol and total serum triglycerides was well demonstrated. It was also shown that the polyunsaturated to saturated fatty acid ratio affects plasma cholesterol levels. A soy protein diet resulted in reductions of more than 15% plasma cholesterol, independent of the P/S ratio.

Not all human studies of soy protein-based diets have shown a significant reduction of plasma cholesterol. Individuals with normal or slightly elevated cholesterol levels would be expected to show less change in cholesterol than individuals with markedly elevated lipids. Individuals with normal cholesterol levels do not always respond with a further decrease in serum lipids. It is not yet clear how soy proteins lower total cholesterol and the LDL fraction but several theories have been postulated.

In 1995, a team of researchers conducted a combined analysis of 38 human trials on soy protein and published their findings in the New England Journal of Medicine. In that landmark analysis, the authors looked at 38 controlled clinical trials reported in 29 scientific articles to determine the relationship between soy protein consumption and serum lipid concentrations in humans. They concluded that the consumption of soy rather than animal protein significantly decreased serum concentrations of total cholesterol, LDL cholesterol, and triglycerides. With the publication of this study, the science of soy protein's action in the human cardiovascular system was retrieved from obscurity, clarified, and appreciated for the first time by the medical community at large for the impact it could have on improving public health.

Studies in animals have shown that soy protein enhances bile acid secretion, which has the effect of removing cholesterol from the blood. Other studies have shown that soy protein stimulates the liver to remove LDL cholesterol from the blood. Researchers have also speculated that soy affects various aspects of the endocrine system, altering concentrations of hormones involved in cholesterol metabolism.

Dietary Fiber

Diets low in dietary fiber have been correlated with increased incidence of colon cancer, coronary heart disease, diabetes, diverticular disease of the colon, and various other maladies of the lower gastrointestinal tract. Many soy protein products can be excellent sources of dietary fiber. Dietary fiber consists of different complex carbohydrates including water soluble and water insoluble compounds. Cellulose, hemicellulose, and lignin are primarily water insoluble fibers. Pectins, gums and mucilages are water soluble components.

Few studies have dealt directly with the nutritional effects of soybean fiber in man. However, there is little argument that dietary fibers have a much greater effect on human nutrition than was previously realized. For example, one human study showed changes in composition and morphology of cereal brans and soybean hulls after passage through the alimentary tract. These materials, incorporated into bread as the major food fiber components of a controlled diet, were retrieved as identifiable particles from the feces of human volunteers. Soybean hulls were found to be well digested by the human alimentary system, with major losses of cellulose and hemicellulose. In other research conducted by the U.S. Department of Agriculture's Northern Regional Research Center, it has been found that soybean hulls are a rich source of Iron, which is easily absorbed by the body.

While there is growing interest in the role fiber plays in promoting general health and preventing disease, much research must be done before these relationships are clearly understood. Many medical and health authorities, meanwhile, are suggesting an increase in consumption of fiber by most of the U.S. population.

Brief History of a Super Food

Although the food use of soybeans in China goes back to ancient times, their history in the Western World dates from the 20th century, with demand increasing as markets developed for the oil and later for the high-quality soybean meal used as a protein source for animal feeds. The industry that produces soy protein products for human consumption has grown enormously since the late 1950's. Current production is about one billion pounds of protein products for human consumption per year in the United States - or about four to five pounds per person.

It is widely accepted that soy originated in northeastern China, just south of Manchuria. The first written record of it appears circa 2800 B.C, in the writings of the Chinese Emperor Shen Nung, who is known as the "Father of Chinese Agriculture." Cultivated now for more than 3,000 years and long held in high regard by Chinese physicians, the soybean has been called "the miracle bean," the "cow of China," and "meat of the fields."

Approximately 38 percent of the soybean's edible weight is protein, three times that of wheat, corn or other cereals. Compared to other foodstuffs it is one of the most inexpensive sources of protein to produce. One calculation conducted in the 1980s estimated that one pound of protein from beef costs $9.90; from medium eggs, $3.99; from milk, $2.61; and from granulated soybeans, 82 cents.

The soybean first made its way to Europe in the 18th century and was regarded primarily as a horticultural curiosity. It was not until 1898 that the U.S. Department of Agriculture began testing soybeans and distributing them to farmers. Many farmers reported that their animals were fond of eating soybeans, yet none at the time considered the novel legume appropriate for human consumption. Corn Belt farmers first embraced the soybean in 1927 because a nasty pest, the European corn borer, had devastated that season's corn crop and soybeans had proven immune. Within two years, farmers were growing 9 million bushels of soybeans. Ten years later, they were growing 99 million bushels and by the middle of World War II, American farmers were out producing their Chinese counterparts. Today, the United States is the top producer of soybeans in the world. It is the country's second largest cash crop, worth $13 billion to the economy. Yet the bulk of this copious output is still primarily destined for export and for processing into animal feed.

The father of soybeans in America was the agronomist William J. Morse, who spent two years in China collecting more than 2000 varieties and types of Glycine max. He spent his career championing soybeans for human consumption. Henry Ford was another serious soybean aficionado. At the Chicago World's Fair in 1934, he invited 30 guests to partake in a l6 course soy dinner.

Since the 1960s, soy protein products have been used as nutritional and functional food ingredients in every food category available to the consumer. The technology needed to produce cereal crops sufficient to meet world food requirements of upcoming generations is available now. Cereals have a low protein content and are imbalanced in essential amino acid composition. Protein production has become the issue of the day as world population grows and the public becomes increasingly aware that the chronic consumption of animal protein is a significant contributing factor in the degeneritive diseases that worry us all. Soy protein products are an ideal source for some of the essential amino acids used to complement cereal proteins. At present, soy proteins outrank many other food proteins in various worldwide nutrition programs.

Quality Human Nutrition

The nutritional value of soy protein products in the human diet has been established by extensive nutritional research with infants, children and adults at research institutes worldwide. The significance for human nutrition of the sulfur containing amino acid content of soy protein products has also been examined. It has been concluded that, for young children and adults, methionine supplementation of products containing soy protein products is not necessary; nor is methionine supplementation of the soy protein products themselves necessary for an adult diet, as was previously believed.

Soy protein products can also be used to increase the total amount of dietary protein available, thus improving human nutrition in mixed foods containing animal protein. Various beef soy combinations will affect protein utilization differently. In a study of young men consuming beef, a 50:50 mixture of beef and soy and milk showed equal nutritional value for the three protein sources. When soy was compared to fish as the sole protein source for humans, equal amounts of protein from both sources elicited a similar nitrogen balance. These results are supported by another study in which a 50:50 mixture of fish and soy isolate was found to be equivalent to fish. The low fat and cholesterol content of fish/soy combinations is claimed by many as a definite advantage to utilizing these as a protein source.
Many applications for soy proteins involve their combination with cereal grains. The addition raises both the quantity and quality of the protein in cereal products. The soy protein amino acid profile which is lysine rich and sulfur amino acid limited fits nicely with grain proteins which are lysine limited and sulfur amino acid rich. The resulting protein quality if properly blended will be superior to either protein consumed alone.

As soy proteins replace traditional protein sources in our diet, and as fiber and whole grain products gain popularity, scientists must consider how these changing dietary patterns affect nutrient bioavailability and, in turn health. Of particular interest is the impact of soy consumption on total nutrition, since trace minerals from vegetable proteins are less readily available for use than those from animal products. Fortification should be undertaken only when consumption is a significant portion of the diet. Indiscriminate fortification could cause alternate mineral deficiencies. For example, calcium addition to diets containing phytate reduces zinc utilization, whereas zinc addition may reduce copper utilization.

Factors Affecting Protein Quality

Soy protein products fall into three major groups. These groups are based on protein content, and range from 40% to over 90%. All three basic soy protein groups are derived from defatted flakes. They are soy flours, soy protein concentrates and soy protein isolates.

Protein nutritional quality is generally determined by three factors: essential amino acid composition, digestibility, and amino acid requirements of the species consuming the protein. In addition, the food system and companion protein quality need to be considered. The amino acid composition requirement of man is not for protein per se, but for specific amounts of indispensable, or "essential," amino acids as the building blocks of protein. Soy proteins provide all the essential amino acids needed to fulfill human nutritional requirements for growth, maintenance, or physical stress. This amino acid pattern is among the most complete of all vegetable protein sources and resembles, with the exception of the sulfur-containing amino acids like methionine, the pattern derived from high-quality animal protein sources. Some have suggested that, when used as the sole source of protein, soy protein products are limited in methionine. However, methionine supplementation of soy protein products in an adult diet is not usually necessary because, at levels normally consumed, soy protein products supply more than an adequate amount of essential amino acids, including methionine. The absence of an ideal balance of essential amino acids for a particular foodstuff need not be a serious limitation since a human diet usually contains a variety of protein sources, such as cereals, beans and animal proteins - each with its own characteristic amino acid pattern. By blending these proteins in a daily diet, a suitable balance of the essential amino acids can be obtained.

Soy proteins can, in fact, enhance the nutritional quality of other vegetable proteins. Amino acids that are limited in other proteins may be present in excess amounts in a soy protein product. For example, soy protein products contain a level of lysine that exceeds human requirements. Hence, supplementation with soy protein products provides an excellent way to correct the lysine deficiency in some protein containing grains, such as wheat or corn. Numerous studies have established the nutritional value of soy protein products in combination with other proteinaceous food ingredients, with or without amino acid supplementation.

According to Susan Potter, Ph.D., a research scientist who serves as director of nutritional science at Protein Technologies International "For soy protein to have a beneficial effect, it must be consumed regularly, though not exclusively, and in sufficient quantity. To eat 25 grams of soy protein every day would pose a challenge to most Americans. While soy protein is available in an increasing variety of products, it has not yet been incorporated into the mass manufacture and marketing of readily available and familiar foods such as baked goods, pastas, cereals and milks. As consumers become aware of the health benefits of soy protein, an opportunity emerges for the food industry to develop soy based foods that will be popular with consumers. The potential impact that this oldest of foods can have on the health and well being of current and future generations is profound."

Soy Bioavailability

There is strong incentive for using low-cost vegetable sources of protein in the world economy. This has prompted segments of the U.S. food industry to focus on vegetable proteins in food formulations. Soy protein products offer more than just the obvious economic advantages that vegetable proteins have over animal proteins. Advances in soy ingredient technology have resulted in products that can perform many functions in foods such as emulsification, binding, and texture. Soy protein product acceptance has grown because of such functional properties, in addition to their excellent nutritional quality, abundance and low cost. However, the full potential of soy proteins for food applications has not yet been realized in regard to functionality, nutrition and new food concepts.

Both human clinical studies and animal research have demonstrated that soy protein products are comparable in digestibility to other high-quality protein sources, such as meat, milk, fish and egg. Studies with 2 to 4 year old children showed that the digestibilities of the different soys tested were equal to or greater than the digestibility of milk proteins at the same intake level. One study used young adult men to evaluate protein digestibility when a commercial soy isolate was combined with beef at graded levels. The digestibility was found to be in the range of 97% to 99%. Another study compared a commercial isolate with egg protein at intake levels ranging from 0.2 to 0.6 gram protein per kilogram of body weight per day. The results indicated that the digestibility of the isolate was 98.4% of the whole egg protein.

Summary data on human studies determining the digestibility of nitrogen are also available for various soy protein products. The digestibility values for children range from 84% for soy flour to 95% for soy isolate. For adults, well processed products from any oilseed can be expected to have values higher than 90%. Digestibility values of soy protein concentrates and isolates for humans fall in the range of 91% to 96%, comparable to the digestibility values for milk.

The nutritional significance of protease inhibitors in human and animal studies have shown soy products to be excellent sources of protein. In most food applications, soy protein products are not used as the sole source of protein, but in combination with other proteins. Many studies have shown soy protein products effectively improve the nutritional value of the food, especially when combined with proteins of cereal origin. In many raw food ingredients, proteins may not be hydrolyzed by digestive enzymes because of the presence of protease inhibitors.

Food allergies are much more common in children than in adults. Cow's milk has been identified as the food allergen most common to children, affecting perhaps as many as 7%. Soy protein formulas are recommended for infants, as well as others, who are allergic to milk protein or who are lactose intolerant. Approximately 10% of formula-fed infants are being fed formulas containing soy protein. For the adult population, the figures for both general and specific food allergies are more uncertain because no reliable epidemiological studies have been performed for this group. The immunochemical reactivity of most of the soybean's protein components are destroyed by heat treatment. Heat processed soy protein products, including soymilk, are generally considered to be hypoallergenic.

Hormones & Isoflavones

Soybeans are unique among beans because they contain compounds called isoflavones. These molecules have structures very similar to the body's natural estrogens hence the name plant or phyto estrogens, major research efforts are directed at understanding what isoflavones do in our bodies when we eat soy. Soy's unique phytochemical, genistein is especially important for both men and women. From this plant nutrient men can look to lower risk for prostate cancer and younger women to lower risk for breast cancer and other estrogen dependent cancers.
All of this indicates that should one desire a healthful alternative to estrogen and progesterone therapy for postmenopausal symptoms, consuming soy with 40-50 mg isoflavone content per day may obviate the need for exogenous hormone drug therapy. Check with your doctor first but soy consumption within a varied diet that includes vitamin and calcium supplementation may be worth a trial before starting hormone therapies.

Researchers are still designing studies to determine the mechanisms through which soy protein with isoflavones exercises its beneficial effects. Because they are structurally similar to mammalian estrogens, it is thought that isoflavones in soy protein work like hormones by binding to specific receptors on cell surfaces and triggering activity. Estrogens are hormones that our bodies make and require for normal growth and development. They maintain good adult health not only in women, but also in men. Estrogens are essential for the female reproductive system, but they are also important for the bones, the heart, and possibly the brain. For women faced with menopause and its loss of estrogens, how to replace estrogens is a major issue. In standard hormone replacement therapy (HRT), the combination of estrogens with synthetic progesterone prevents osteoporosis. It also largely overcomes the increased risk of uterine cancer from using estrogens alone. Combination HRT is less effective than estrogens alone in protecting against heart disease.

Estrogens work with complex proteins called estrogen receptors. These proteins dock at sites within selected genes in the cell's nucleus, switching those genes on or off. This switching makes cells proliferate like breast growth during puberty or causes them to differentiate and make special products for example, milk following pregnancy. There are two estrogen receptors, alpha and beta, and predominates in certain estrogen responsive tissues, such as bone and the bladder.

Soy isoflavones fit into estrogen action through genistein, the most abundant isoflavone in soybeans. It binds only weakly with estrogen receptor alpha, but binds with estrogen receptor beta almost as well as estrogen does. This probably explains genistein's ability to prevent bone loss in ovariectomized rats. The predominance of estrogen receptor beta in the cardiovascular system suggests that soy isoflavones may be partly responsible for the lower incidence of heart disease in soy consuming countries.

In other countries particularly in Southeast Asia where soy consumption is high, the incidence of breast, prostate and uterine cancer is substantially lower than in the USA. A group of white Australian women whose diets included higher amounts of isoflavones and other phytoestrogens had a lower incidence of breast cancer. Interestingly, the intake of soy in these women was less than one serving per day. This could mean that eating soy and its isoflavones protects us from cancer. Conclusive evidence cannot be given at this time, since the observed beneficial effects could be the result of associated dietary and lifestyle factors. It should also be noted that using concentrated isoflavone preparations extracted from the soybean leaves behind the rest of the phytochemicals in soy foods that have health benefits.

Isoflavones appear to work in ways that are non-hormonal as well. In the test tube, genistein has been able to prevent a process called phosphorylation from taking place, in essence shutting off a chemical message that stokes inflammation of arterial walls. Researchers in Finland have found that isoflavones protect cholesterol from oxidation. LDL cholesterol only becomes harmful when it is oxidized as a result of reacting chemically in the blood with molecular fragments known as free radicals. Once oxidized, LDL cholesterol can provide the raw ingredients for plaque.

The isoflavone genistein is also known to shut down the action of tyrosine kinase, a protein crucial in the cascade of biochemical events that result in the formation of adhesive clots and lesions in the bloodstream. In addition, researchers suspect that genistein can reduce inflammation of arteries following balloon angioplasty and stent placement and decreases the high rates of failure associated with those expensive and invasive cardiovascular procedures. Genistein is a chemical compound found only in soy in our daily foods. Dr. Lothar Schweigerer at Heidelberg University discovered that genistein blocks an event called angiogenesis, the growth of new blood vessels that nourish malignant tumors. Once a tumor grows beyond a millimeter, it must foster the growth of new blood vessels into it in order to become malignant and life threatening. By inhibiting blood vessel growth, genistein may keep new tumors from growing beyond harmless dimensions and eventually lead to shrinking of the tumor. These discoveries could have important implications for treatment of solid tumors, including malignancies of the breast, prostate, colon and brain.

Other investigators have confirmed that soy's isoflavones improve the elasticity of arterial vessels, which otherwise stiffen with advancing age. Other components of soy protein, aside from isoflavones, also are under investigation for their potential beneficial effects. Some studies indicate that the particular ratio of the different amino acids to be found in soy protein might play a role in reducing cholesterol. Certain amino acids especially lysine increase blood cholesterol levels, while arginine counteracts this effect. Soy protein contains a greater arginine to lysine ratio than animal protein, but this fact alone does not sufficiently account for soy's hypocholesterolemic effects.

New frontiers in the field of nutrition will be explored as we learn more about specific phytochemicals such as isoflavones. Phytochemicals are non-nutritive, meaning they are neither vitamins nor minerals. There are many hundreds of these bioactive plant chemicals found in dietary sources of fruits, vegetables, legumes, whole grains, nuts, seeds, herbs and spices. Isoflavones have received a great deal of research, especially for their possible cancer and heart disease preventing properties. To date, most of the research has been done in animals, cell culture and in vitro studies. There are many types of phytoestrogens and not all are in edible plants. Isoflavones are found in chick peas and other legumes. The soy bean has the most concentrated amount of them all.