Consumers are becoming increasingly interested in healthful foods and are open to soy protein in- gredients. Soybeans as food are very versatile and a rich source of essential nutrients. They are also an excellent source of good-quality protein, comparable to other protein foods, and suitable for all ages. Adverse nutritional and other undesirable effects followed by the consumption of raw soybean meal have been attributed to the presence of endogenous inhibitors of digestive enzymes and lectins, as well as poor digestibility. To improve the nutritional quality of soy foods, inhibitors and lectins are generally inactivated by heat or eliminated by fractionation during food processing. Soybeans provide an alternative source of protein for people who are allergic to milk protein. Soy protein is highly digestible (92% to 100%) and contains all essential amino acids. Although relatively low in methionine, it is a good source of lysine. Soy-protein products contain a high concentration of isoflavones, up to 1 g/kg. Increased acceptance of soy proteins is due to unmatched qualities like good functional properties in food applications, high nutritional quality, abundance, availability, and low cost. At present the various forms of soy proteins are primarily utilized for their functional effects rather than their nutritional properties. This article summarizes the integrated overview of the widely available, scattered information about the nutritional and functional uses of the soy proteins when applied in food systems and intends to present the most current knowledge with an interest to stimulate further research to optimize their beneficial effects.

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Functional and Edible Uses of Soy Protein Products

Antioxidants are considered as the most promising chemopreventive agents against various human cancers. However, some antioxidants play paradoxical roles, acting as "double-edged sword." A primary property of effective and acceptable chemopreventive agents should be freedom from toxic effects in healthy population. Miscarriage of the intervention by β-carotene made us realize the necessity for evaluation of safety before recommending use of antioxidant supplements for chemoprevention. We have evaluated the safety of antioxidants on the basis of reactivity with DNA. Our results revealed that phytic acid, luteolin, and retinoic acid did not cause DNA damage under the experimental condition. Furthermore, phytic acid inhibited the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an indicator of oxidative DNA damage, in cultured cells treated with a H2O2-generating system. Thus, it is expected that these chemopreventive agents can safely protect humans against cancer. On the other hand, some chemopreventive a...

Evaluation for safety of antioxidant chemopreventive agents.

Influence of extremely low frequency magnetic fields on Ca2+ signaling and NMDA receptor functions in rat hippocampus.

Phytoestrogens have the potential to maintain bone health and delay or prevent osteoporosis. This review focuses on their dose-dependent effects on bone and their possible mechanisms of action. Phytoestrogens exert biphasic dose-dependent effects on osteoblasts and osteoprogenitor cells, stimulating osteogenesis at low concentrations and inhibiting osteogenesis at high concentrations. They inhibit osteoclast formation and activity. Recent data show that the balance between estrogen receptors and peroxisome proliferator-activated receptors, which are dose-dependently activated by phytoestrogens, determines their biological effects on bone. This review provides a new understanding of the mechanism of action of phytoestrogens and could be important for future studies to find precise beneficial doses in vivo and in clinical trials.

https://www.cell.com/trends/endocrinology-metabolism/pdf/S1043-2760(05)00096-2.pdf

Dose-dependent effects of phytoestrogens on bone.

The soy phytoestrogen daidzein has biphasic dose responses, but the underlying mechanisms are not yet clear. Transcriptional and biochemical data show that PPARs, in addition to ERs, are molecular targets of daidzein, which divergently regulates osteogenesis and adipogenesis. Dose responses are the result of a balance among PPARs and between ERs and PPARs.



Introduction: Soy phytoestrogens have been used for the purposes of treatment and prevention of osteoporosis. Biphasic dose responses of daidzein, one of the main soy phytoestrogens, have long been recognized, but the underlying molecular mechanisms of action are not yet clear.



Materials and Methods: Mouse bone marrow cells and mouse osteoprogenitor KS483 cells that concurrently differentiate into osteoblasts and adipocytes were cultured. Biochemical measurement of alkaline phosphatase (ALP) activity, RT-PCR, and gene reporter assays were used in this study.



Results: Daidzein, one of the major soy phytoestrogens, had biphasic effects on osteogenesis and adipogenesis. Daidzein stimulated osteogenesis (ALP activity and nodule formation) and decreased adipogenesis (the number of adipocytes) at concentrations below 20 μM, whereas it inhibited osteogenesis and stimulated adipogenesis at concentrations higher than 30 μM. When estrogen receptors (ERs) were blocked by ICI182,780, daidzein-induced effects were not biphasic. A decrease in osteogenesis and an increase in adipogenesis were observed at the concentrations higher than 20 and 10 μM, respectively. In addition to ERs, daidzein transactivated not only peroxisome proliferator-activate receptor γ (PPARγ), but also PPARα and PPARδ at micromolar concentrations. Activation of PPARα had no direct effects on osteogenesis and adipogenesis. In contrast, activation of PPARδ stimulated osteogenesis but had no effects on adipogenesis, whereas PPARγ inhibited osteogenesis and stimulated adipogenesis. Transfection experiments show that an activation of PPARα or PPARγ by daidzein downregulated its estrogenic transcriptional activity, whereas activation of PPARδ upregulated its estrogenic transcriptional activity. Activation of ERα or ERβ by daidzein downregulated PPARγ transcriptional activity but had no influence on PPARα or PPARδ transcriptional activity.



Conclusions: Daidzein at micromolar concentrations concurrently activates different amounts of ERs and PPARs, and the balance of the divergent actions of ERs and PPARs determines daidzein-induced osteogenesis and adipogenesis.

https://asbmr.onlinelibrary.wiley.com/doi/pdf/10.1359/jbmr.040120

Xue-Yan Wang

Papers

Daidzein enhances osteoblast growth that may be mediated by increased bone morphogenetic protein (BMP) production.