Synonyms/Common Names/Related Substances:

• Abalone®, beta-conglycinin, bioactive peptides, bowman-birk inhibitor (BBI), coumestrol, daidzein, daizuga-cha (Japanese), dark soy sauce, dietary soy protein, edamame, equol , Fabaceae, flavonoids, fortified soy milk, frijol de soya, functional proteins, genistein, genistin, Glycine max, greater bean, haba soya, hydrolyzed soy protein, isoflavone, isoflavones, isoflavonoid, Isomil®, kuromame-cha (Japanese), kuromame-cha Gold (Japanese), kuromame-soy milk drink (Japanese), lecithin, legume, lignans, margarine, miso, Mull-Soy®, natto, Nursoy®, okara, phosphatidylserine, phytate, phytoestrogen, plant estrogen, PtdSer, S-PtdSer, shoyu, shoyu polysaccharides, soja, sojabohne, soya, soya-based food, soya protein, soya sauce, soybean, soybean-barley paste, soybean oil, soy milk, soy fiber, soy flour, soy food, soy isoflavones, soy lecithin, soy milk, soy nuts, soy oil, soy phosphatidylcholine complex (IdB 1016), soy phosphatidylinositol (PI), soy product, soy protein, soy protein isolate, soy sauce, Supro®, Ta-tou, tempeh, texturized vegetable protein, tofu, yuba.
• Note: Ipriflavone, a synthetic isoflavone, has been studied as a possible way to treat or prevent bone loss in post-menopausal women. This monograph concentrates on natural soy. Ipriflavone is discussed separately. Soy isoflavones, genistein and daidzein, have been studied as treatments for various conditions. This monograph concentrates on soy protein or foods containing soy protein. Isoflavones are discussed separately. Soy lecithin is derived from the processing of soybeans. It is a mixture of fatty substances separated from soybean oil and used as a food additive. Its chemical name is phosphatidylcholine and contains the constituents of choline, phosphoric acid, glycerin, and fatty acids. Soy lecithin is discussed in a separate monograph. Soybean oil and soy-derived sterols are not specifically discussed.

Clinical Bottom Line/Effectiveness

Brief Background:

• Soy is a subtropical plant, native to southeastern Asia. This member of the pea family (Fabaceae) grows from one to five-feet tall and forms clusters of three to five pods, each containing two to four beans per pod. Soy has been a dietary staple in Asian countries for at least 5,000 years, and during the Chou dynasty in China (1134-246 B.C.), fermentation techniques were discovered that allowed soy to be prepared in more easily digestible forms such as tempeh, miso, and tamari soy sauce. Tofu was invented in 2^nd-Century China. Soy was introduced to Europe in the 1700s and to the United States in the 1800s. Large-scale soybean cultivation began in the United States during World War II. Currently, Midwestern U.S. states produce approximately half of the world's supply of soybeans.
• Soy contains protein, isoflavones, and fiber, all thought to provide health benefits. Soy is an excellent source of dietary protein, including all essential amino acids. Soy is also a source of lecithin or phospholipid. Soy isoflavones and lecithin have been studied scientifically for numerous health conditions. Isoflavones such as genistein are believed to have estrogen-like effects in the body, and as a result are sometimes called "phytoestrogens." In laboratory studies, it is not clear if isoflavones stimulate or block the effects of estrogen, or both (acting as "mixed receptor agonists/antagonists"). In Japan, dietary levels of isoflavones are estimated to be between 20-80mg per day as opposed to less than 1mg daily in North America (1). This monograph will concentrate on the effects of soy foods and soy protein and not soy components such as lecithin or isoflavones.
• Common sources of soy isoflavones include roasted soybean, green soybean, soy flour, tempeh, tofu, tofu yogurt, soy hot dogs, miso, soy butter, soy nut butter, soy ice cream, soy milk, soy yogurt, tofu pups®, soy cheese, bean curd, seitan, and soy noodles. Soybean flour is found in Spanish sausage products (chorizo, salchichon, mortadella, and boiled ham), doughnuts, and soup stock cubes (2). Although processed soy foods (e.g., veggie burgers, tofu pups®, meatless dinner entrees, chicken-free nuggets, soy "ice creams" and energy bars) are usually high in protein, they typically contain lower levels of isoflavones (3). Textured vegetable protein produced from soy flour and soy isolates are expected to contain isoflavones while those produced from soy concentrate usually have none (4). No difference in satiety has been found between egg albumin, casein, gelatin, soy protein, pea protein, and wheat gluten (5).
• There is currently an approved health claim for soy (25g daily) for cholesterol reduction in the United States (6), and there is clinical evidence to support the use of soy protein as a lipid-lowering agent (7;​8). Based on epidemiological study (NHANES I Epidemiological Follow study), dietary intake of legumes, including soy, have been associated with a reduced risk of cardiovascular disease.
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Dosing/Toxicology

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Precautions/Contraindications

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Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

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Mechanism of Action

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History

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Evidence Table

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Evidence Discussion

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Products Studied

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Author Information

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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