All about soya as a wonder food
SOYA
Improves bone health
Reduces risk of osteoporosis
Assists in reducing menopausal symptoms
Prevents calcium loss
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, and substantial amounts of fat, carbohydrates, dietary fiber, vitamins, minerals and a virtual drugstore of phytochemicals useful for the prevention and treatment of many chronic diseases.
Soybeans vary widely in nutrient content based on the specific variety and growing conditions, but typically they contain 35-40 percent protein, 15-20 percent fat, 30 percent carbohydrates, 10 to 13 percent moisture, and around 5 percent minerals and ash.
Elements of the Bean
Soy Protein
The protein in the soybean contains all of the essential amino acids necessary for humans, and can sustain health at all stages of development. Using the protein digestibility corrected amino acid score (PDCAAS) method, soy protein products generally receive scores of between 0.95 and 1.00, the highest value possible.
The soyabean is very high in protein (38%). So whole soyabeans and traditional soya foods, such as tofu, tempeh and soya milk are good protein sources. But it is not only the total amount of protein that is important, you also have to take the quality of the protein into account.
Currently, a PDCAAS (protein digestibility corrected amino acid score) is used to evaluate protein quality. This evaluation takes into account the amino acid composition and the digestibility of the protein.
The protein digestibility of most soya products is generally excellent. In fact, the digestibility of soya protein is comparable to milk and meat proteins and can reach 100%.
The chemical index or amino acid score is the ratio of the most limiting essential amino acid, calculated by comparing content of the protein with that of amino acid requirements as defined by the FAO / WHO / UNU (Food and Agriculture Administration / World Health Organisation / United Nations University). Different needs for different age groups have been defined.
The digestibility and chemical index together determine the PDCAAS value of the protein. The theoretical maximum value is 1.
The protein in most soya products has a PDCAAS that approaches a score of 1.0, indicating that both amino acid pattern and digestibility of soya protein are excellent (1,2). In addition to helping to meet the biological requirement for protein consuming soyfoods is an excellent way to increase the protein content of the diet as means of maintaining ideal weight. Research suggests that higher protein diets are more satiating and useful for weight management (3). Although high protein diets may increase risk of developing kidney disease in susceptible individuals (4), several studies indicate that soya protein favorably affects renal function in comparison to animal proteins (5-8).
The American Food and Drug Administration and the British Joint Health Claim Initiative approved the health claim that "Intake of 25 grams of soya protein a day, as part of a diet low in saturated fat, may reduce the risk of heart disease".
Soy Oil
Soybeans, in comparison to other beans, grains and cereals, contain a high amount of fat. Fortunately, the fat found naturally in the soybean, and that which ends up in whole soybean-based foods (and most traditionally processed soyfoods such as tofu, soymilk, tempeh, full fat soy flour, and liquid soybean oil) can be categorized as a healthy fat.
Approximately 50 percent of the fat in soybeans is linoleic acid, a polyunsaturated fat and an essential nutrient. In addition, soybean oil can contain as much as 8 percent alpha-linolenic acid, which is an Omega-3 fatty acid, the type of fat found in fish which is believed to be beneficial in lowering the risk of heart disease.
Carbohydrates and Fiber
Unlike other beans, there are few complex carbohydrates in soya. Soyabeans contain 10-13% carbohydrates of which sugars represent 10-12% and starch 1%. The soyabean also contains 18% fibres, a mixture of cellulosic, and noncellulosic structural components of the internal plant cell wallSoluble and insoluble carbohydrates, including dietary fiber, make up about 30 percent of the soybean. The primary soluble carbohydrates in the soybean are the sugars stachyose, raffinose and sucrose. The amounts of these sugars vary according to both the variety of soybean and its growing conditions, but for the most part, together, they make up about 10 percent of the soybean.
The oligosaccharides raffinose and stachyose are significant because they are not digested or used as nutrients directly by the human body, but instead are used as nutrients by the bifido bacteria in the lower intestine to sustain and promote their growth. These types of intestinal flora are considered important for human health, as it is believed that their presence can reduce the incidence of many diseases of the lower tract, including colon cancer.
Vitamins and Minerals
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 be very rich sources of any one particular vitamin, they do contribute to an overall nutritional well-being.
The water-soluble vitamins in soybeans are thiamine, riboflavin, niacin, pantothenic acid, biotin, folic acid, inositol and choline. 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 or dry soybean. Tocopherols are an important constituent of soy oil due both to the vitamin E supplied for human nutrition and the antioxidant properties of tocopherols that protect the oil.
Calcium
The soya bean is a good source of calcium (Ca) and contains approximately 225 mg Ca/ 100 g beans. The content of soya drinks, however, is only 12-mg/100 g, so to be a good source of calcium and obtain the same quantity as in cow's milk, soya drinks have to be enriched with calcium.
The bioavailability of calcium (the quantity available to be used in the biological processes), is very important. It is sometimes heard that the bioavailability of calcium from soya milk isn't as high as from dairy milk.
Research revealed that the bioavailability of calcium is comparable, and that both are good sources of calcium.
Isoflavones
Isoflavones belong to the 'phyto-estrogens', plant compounds with a chemical structure similar to the endogenous estrogen, oestradiol (see figure). The importance of this structural similarity and its possible favourable effect on hormone-dependent cancers was first discussed in the 1980s. Phyto-estrogens are very common in plants. Large differences however exist in the concentration and type of phyto-estrogens according to the plant, growing conditions etc. In food research 3 groups of phyto-estrogens get particular attention: isoflavones, coumestans and lignans.
Lignans occur mainly in cereals, fibre, fruit and vegetables under the form of precursors. These are metabolised by the gut flora to enterolactone and enterodiol. Flaxseed is a rich source of lignans.
Coumestans are found mostly in alfa-alfa and animal feed. The content is however strongly dependent upon growing conditions, such as moisture.
Soy isoflavones are not only special because of the effect they are believed to have on health, but also, because for all practical purposes, no other food contains as significant an amount of these chemicals as does the soybean.
The major isoflavones in soybeans are genistein, daidzein and glycitein. Of these, it is genistein which is believed to have the most potential to prevent or treat certain cancers. Isoflavones are also sometimes referred to as phytoestrogens, meaning plant estrogens, because they have a similar chemical make-up as does estrogen (although the estrogenic effect of isoflavones is approximately one thousand times weaker than the natural hormone).
The soya bean is unique as it contains the highest levels of isoflavones. Soya contains three types of isoflavones; genistein, daidzein and to a lesser extent glycetein. They appear mostly in the form of sugar conjugates called beta-glucoside conjugates (1,2).
Bioavailability which is crucial for clinical effectiveness of soya isoflavones is dependent on intestinal metabolism because the intact beta-glucosides cannot be absorbed into the bloodstream (2). Hydrolysis of these sugar groups is an essential first step for absorption and activation of their biological activity and this occurs along the length of the intestine by the action of specific beta-glucosidase enzymes located on the mucosal membrane (3). Further, metabolic transformation of soya isoflavones takes place by the action of intestinal bacteria leading to the formation of many isoflavone metabolites (4,6). One of these metabolites, equol, has been found to possess even greater biological activity than its precursor in soya, daidzin (7).
Isoflavones have a low estrogenic potency; 1/10 000 to 1/140 000 of the activity of oestradiol, the major endogenous estrogen. While isoflavones, can behave as estrogen agonists, they may also antagonize the action of estrogens in certain tissues. The reason for this is complex but partly explained by a unique property of isoflavones. Unlike the body's steroidal estrogens, isoflavones have selective estrogen receptor modulatory (SERM) action (7) and show a higher affinity for the estrogen receptor subtype ERb than for ERa (8). Estrogens on the other hand bind with equal affinity to both ERa and ERb. A further distinction between estrogens and isoflavones relates to their conformational fit into the pocket and binding site of the dimerized estrogen receptor (9). Isoflavones such as genistein differ significantly from estradiol in this regard and this from that influences the recruitment of co-activators or co-repressors to the complex, resulting in differences in transcriptional activity. Isoflavones appear to show binding similarities to the SERM, raloxifene (10) and not to estradiol. In tissues where there is an abundance of ERb, such as bone, brain, vascular endothelium and bladder, soya isoflavones are likely to exert estrogen agonist action while in tissues rich in ERa it is probable that isoflavones antagonize the action of estrogen. The presence or absence of estrogens and the receptor number and distribution may also influence the overall action. The picture is by no means simple but what is clear is that soya isoflavones should not be viewed as being comparable estrogens.
They appear to be without the negative effects of estrogens used in hormone therapy, which has invoked so much fear in women due to the recent negative findings from the large clinical studies of hormone replacement therapy.
SOY LECITHIN COMPOSITION
Soy lecithin consists of three types of phospholipids; phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphotidylinositol (PI). It is extracted from soybean oil and is generally used as a natural emulsifier or stabilizer in various food applications.
PROCESSING
Lecithin is a combination of naturally-occurring phospholipids, which are extracted during the processing of soybean oil. The soybeans are tempered by keeping them at a consistent temperature and moisture level for approximately seven to 10 days. This process hydrates the soybeans and loosens the hull. The soybeans are then cleaned and cracked into small pieces and the hulls are separated from the cracked beans. Next, the soybean pieces are heated and pressed into flakes. Soybean oil is extracted from the flakes through a distillation process and lecithin is separated from the oil by the addition of water and centrifugation or steam precipitation1.
FUNCTIONAL BENEFITS
Lecithin is utilized in a wide variety of food and industrial applications. The French scientist, Maurice Gobley, first discovered the substance in 1850, and named it "lekithos," the Greek term for egg yolk. At the time, eggs provided a primary source of commercially-produced lecithin. Today, the majority of lecithin used in food applications is derived from soybeans.
Soy lecithin offers a multifunctional, flexible and versatile tool. It is probably best known for its emulsifying properties, which help promote solidity in margarine and give consistent texture to dressings and other creamy products. Lecithin is also used in chocolates and coatings and to counteract spattering during frying. Additionally, its unique lipid molecular structure makes lecithin useful for pharmaceutical and cosmetic applications and various industrial uses such as paints, textiles, lubricants and waxes.
HEALTH BENEFITS & CLAIMS
Lecithin provides an excellent source of choline, which is essential to every living cell in the body and is one of the main components of cell membranes. Not only is dietary choline important for the synthesis of the phospholipids in cell membranes, it is also necessary for methyl metabolism, cholinergic neurotransmission, transmembrane signaling, and lipid-cholesterol transport and metabolism2. Without choline, the cell membranes would harden, prohibiting important nutrients from entering and leaving the cell. Scientists believe lecithin and choline may aid in memory and cognitive function, cardiovascular health, liver function, reproduction and fetal development and physical and athletic performance.
In 1998, the Institute of Medicine (IOM) of the U.S. National Academy of Sciences identified choline as an essential nutrient and recommended daily intake amounts3. And, in 2001, the U.S. Food and Drug Administration (FDA) approved a nutrient content claim for choline, enabling food manufacturers to inform their consumers via the food label. Foods that contain over 110 mg of choline per serving may claim that they are an "excellent source of choline" and those with over 55 mg may claim that they offer a "good source of choline4."
ALLERGENICITY
The allergens in soybeans reside in the protein fraction of the bean. The allergenic potential of specific soyfoods and/or ingredients is largely based on processing techniques and the amount of protein or protein residue remaining in the final product5. The majority of soy lecithin used in food applications is derived from refined soybean oil that has been processed using the hot-solvent extraction technique, which eliminates most, if not all, allergenic proteins.
In 1998, Awazuhara et al published a study on the antigenicity of the residual proteins in soy lecithin and soybean oil, in which they tested soybean-sensitive individuals for reactions to soybean oil and soy lecithin. Researchers investigated the IgE- and IgG4-binding abilities of the soy lecithin and concluded that the proteins in soy lecithin have little antigenicity in regard to soybean allergy6.
Although limited data exist on the allergenicity of soy lecithin, Steve Taylor, PhD, head of the Department of Food Science and Technology at the University of Nebraska and co-director of the Food Allergy Research Resources Program, concludes that, "avoidance is probably unnecessary for most soy-allergic individuals7."
CONCLUSION
Soy's healthy image extends beyond soyfoods and carries over to byproducts of the bean itself, such as soybean oil and lecithin. The discovery of specific health benefits continues, making soy a welcome sight on ingredient labels. Not only does soy present a potential marketing advantage, but the abundant supply of soybeans guarantees that ingredients such as lecithin are readily available and cost effective.
The Soybean's Effect on Health
Cardiovascular Disease
In 1995 a meta-analysis of previous studies entitled "Health Benefits of Soy Protein" (written by Dr. James Anderson of the University of Kentucky) was published in the prestigious New England Journal of Medicine. Dr. Anderson's study found that soy protein intake was associated with a 9.3 percent reduction in serum cholesterol, a 12.9 percent reduction in LDL cholesterol, and a 10.5 percent reduction in serum triglycerides. For HDL, the "good" cholesterol, concentrations increased by 2.4 percent. It is estimated that this serum cholesterol modification has the potential to reduce risk for coronary heart disease by 18 to 28 percent. Based on the findings from 34 out of the 38 studies reviewed, Dr. Anderson concluded that soy protein was clearly potent in decreasing LDL-cholesterol levels.
But the positive effect of the soybean on heart health is not solely due to the protein and its related compounds; the fats that are found naturally in the soybean also can contribute to a reduction in cholesterol levels. It is understood now that oils that are high in unsaturated fatty acids, such as soybean oil, tend to decrease total serum cholesterol levels. Soybean oil contains about 50 percent linoleic acid, an essential polyunsaturated fat. In addition, soybean oil also contains about 8 percent linolenic acid, which is an omega-3 fatty acid, such as that found mainly in fish oils. This fatty acid has been the subject of numerous studies that link its consumption with a decreased incidence of heart disease and cancer. Soybeans are one of the few plant sources of omega-3 fatty acids.
Osteoporosis
Consumption of soyfoods may help to maintain and even rebuild bone density and strength, and act as an effective treatment for osteoporosis.
Studies have shown that diets high in animal protein tend to cause more calcium to be leached from the bones and excreted in the urine and feces. On the other hand, protein from soybeans does not have this effect. Other studies have shown that the isoflavone genistein inhibited bone breakdown and may increase bone density as well.
Much attention has been focused on the need to increase calcium intake to help prevent osteoporosis, and most people tend to focus on dairy products as the best source for calcium. But many soyfoods are naturally rich in calcium, and the calcium from soyfoods is absorbed as well as that which comes from milk. Among soyfoods, good sources of calcium are tofu (in particular, tofu which has been coagulated with calcium sulfate), calcium-fortified soymilk, whole soybeans, soy flour and tempeh.
Malnutrition
Soybeans can produce at least twice as much protein per acre than any other major vegetable or grain crop, 5 to 10 times more protein per acre than land set aside for grazing animals to make milk, and up to 15 times more protein per acre than land set aside for meat production.
Adding soy protein to breads, tortillas, corn meal, pasta, milk or any traditional food is a low cost and efficient way to ensure adequate nutrition for vulnerable populations. In this manner, not only do people receive enough high quality protein for the development and maintenance of their health, but they also get the added disease prevention benefits of soybean phytochemicals.
Cancer
Since 1990, there have literally been thousands of studies conducted by researchers around the world hoping to identify which of these compounds may be the most valuable in the fight against cancer. And although it is not yet certain which one of these compounds is the most important, or if in fact some or all of them work together to a certain extent, many researchers believe that it is the isoflavones which are responsible for much of the anti-carcinogenic effect. Interestingly enough, soybeans are one of the few widely consumed foods that contain a significant amount of isoflavones.
Because they look similar in structure, isoflavones tend to bind with the receptors normally used by estrogen to exert its effects on the body, some of which are cancer promoting. By binding to these receptors in place of the estrogen, the soybean's phytoestrogens have in essence acted as anti-estrogens.
These protective estrogen-related effects of isoflavones are not just beneficial to woman. It is possible that isoflavones may also exert a therapeutic effect for men with prostate cancer, as estrogen has been shown to be an effective therapy for treating that cancer.
In experiments on human prostate cancer cells, genistein has been shown to inhibit cell proliferation. And in addition, genistein has been shown to inhibit angiogenesis, or new tumor vessel growth, thereby slowing the progression of existing cancer.
Research on soybeans and soyfoods continues to probe their role in the prevention and treatment of disease. For men, women and children, soybeans appear to be one of nature's healthiest and highest quality food sources.
Soya protein is emerging as one of the great alternative protein sources for human consumption. 
