Isolated soy protein is an extract of soy containing 92% protein; by contrast, soy concentrate is 65%. Isolated soy protein is typically used commercially in meal replacements and snacks; at home it is usually added to foods or shakes as a protein source or meat extender.
About 85% of all soy produced is now fed to livestock. Replacing some or all of the meat, which is an inefficient use of the vegetable protein destined for human consumption, is being proposed by some as the single most healthy change that could be made to the Western diet.
Isolated soy protein's amino acid profile exceeds FAO/WHO/UNU minimum recommendations for all essential amino acids for preschool and school age children, and for adults.
Isolated soy protein also has the highest possible Protein Digestibility-Corrected Amino Acid Scores (PDCAAS) -- equal to milk and eggs, better than beef. The PDCAAS is mandated by the FDA as the measure of protein digestibility.
Method of Action
In addition to serving as a major protein source, isolated soy protein provides a wide variety of phytonutrients (plant-derived nutrients) with specific biological actions.
Scientists have found that several components of soy protein may help reduce cancer risk. These include isoflavones (especially genistein), methionine, phytic acid, and protease inhibitors.
Genistein may interfere with an enzyme required for cancer cell growth (protein tyrosine kinase). The tumors are rendered incapable of stimulating new blood vessels to support its growth. It may also block the growth of estrogen-dependent cancers.
Methionine, which is abundant in soy, appears to inhibit the development of breast cancer.
Pytic acid may help prevent the oxidation of dietary iron, thus preventing production of possibly carcinogenic free radicals.
Cholesterol and Heart Disease
Soyfoods, particularly soy protein, may also contribute to reduced risk because they are an excellent, low fat source of protein, and typically replace high-fat meats in the diet.
Several components of soy protein help lower cholesterol. These include the amino acids and peptide fractions in soy protein, and the isoflavones (such as genistein and daidzein) and other cofactors. in addition to lowering cholesterol.
Soy protein may also help to keep blood vessels clear in other ways:
Soy isoflavones have been shown to inhibit oxidation of LDL cholesterol, a major specific source of plaque.
Supporting the functioning of both the inner lining of blood vessels, and their smooth-muscle cells, which help keep blood moving.
Affecting the macrophages and T-cells which infiltrate the lesions (damaged surfaces) in blood vessels that can cause plaque to form.
Female Hormonal Balance
The traditional Japanese diet is rich in soy proteins. And, there is no word for "hot flashes" in the Japanese language!
Phyto-estrogens in the Japanese diet is ne reason why Japanese women have less severe menopausal symptoms than Canadian and other Western women. They compared relative hormone levels by measuring how much was eliminated from the participants' bodies. The Japanese women eliminated the isoflavones genistein, daidzein and equol at 100 to 1000 times the levels of the hormonal estrogens eliminated by the meat-eating Western women.
Asian women are also said to have longer menstrual cycles, apparently due to their high isoflavone diet. One sign of menopause is often shortened or irregular menstrual cycles.
Research indicates that isoflavones are similar enough to real estrogen that they can attach to the places where the hormone usually goes, leaving the hormone with no place to attach to. The locations which protect against hot flashes and the loss of bone density can be activated by the weaker phyto-estrogen. However, the locations where real estrogen can trigger cancer are less likely to be activated by the isoflavone, thus reducing the risk.
Genistein, the major soy isoflavone, stimulates bone formation. Only 40 grams (1½ ozs)of isolated soy protein per day increased bone mineral content and density.
A drug used widely in Europe to treat osteoporosis, which prevents bone from breaking down, is metabolized to daidzein (another soy isoflavone) in the body.
Balanced protein, from whatever sources, is important for maintaining health, especially the following groups: those who are lactose- or milk protein-intolerant; those on a vegetarian diet; recovering from surgery; safe weight loss; etc.
Vegetarians and lactose- or milk protein-intolerant people (most are):
Isolated soy protein is a safe, complete protein replacement source, and very benefical environmentally. (Soy feeds far more people per acre and per gallon of water used than meat, and it is an ideal soil conditioner, fixing more nitrogen than it uses.)
Fitness training physical labor
Adequate protein is essential to support fitness training and hard physical labor.
Protein requirements are based on total energy needs, body mass, type of activity, level of training, age, sex, and climate, temperature and altitude. Isolated soy protein has been proven to enhance athletic performance, especially where endurance and/or strength are critical factors.
Exercise results in an increased oxidation rate (how fast they are used up) for the branched chain amino acids (leucine, isoleucine and valine).
The anabolic effect of training may be influenced by adequate levels of testosterone, growth hormone and insulin in the blood. Arginine, lysine and ornithine may stimulate release of testosterone, growth hormone or insulin and promote muscle development. Isolated soy protein is high in these amino acids also, surpassing casein, whey and egg white and almost as high as beef.
Recovery from surgery and other severe trauma:
Muscle wasting (catabolism) is a serious problem after surgery and other severe trauma. Isolated soy protein and complete soy foods (with fiber and fats left in) can be useful in protecting against loss or restoring original muscle mass, when added to the diet in sufficient quantities.
Isolated soy protein is effective in maintaining nitrogen balance and normal biochemical parameters as part of a balanced, low-calorie diet.
Studies have demonstrated that isolated soy protein is a safe, high quality, complete protein, comparable in quality to milk, meat and egg proteins which fully meets the protein requirements of normal healthy infants, preschool children, and adults.Abstracts
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