Equol is a potent metabolite of the soy isoflavone daidzein, found in soybeans and soy products. Equol is produced through intestinal bacterial metabolism in a small percentage of the adult human population. Research suggests 25 – 30% of the Western population and 50 – 55% of the Asian population produces equol when fed soy products, suggesting a link between the regular consumption of soy and the frequency of equol producers. Previously, equol has been of interest in relation to its antioxidant and hormone-like activity to support menopausal symptoms, however recent applications have observed anabolic effects with the supplementation of equol.
Equol is a selective estrogen receptor modulator, demonstrating estrogenic activity due to the near identical chemical structure to 17-β-estradiol. Equol is present in two corresponding isomers, S-equol and R-equol, with different binding affinities for estrogen receptors. S-equol preferentially binds to Estrogen Receptor β (ER-β) and R-equol preferentially binds to ER-α.
Anabolic effect
The potential of equol to present anabolic effects is promising. Androgens are steroid hormones that play a role in the development and function of reproductive organs, particularly in males. The role of androgens, including testosterone, is to present primary and secondary male sex characteristics, particularly the support of muscle function and strength.
Research has demonstrated the mechanism by which equol and other phytoestrogens can mediate these androgenic effects. With increased levels of plasma daidzein, the activation of androgen receptor coactivators in the PC-3 cell lines work to promote androgenic activity. The outcome of anabolic effect through this pathway of androgen receptor transcription is promising evidence for muscle growth and strength with the supplementation of daidzein and/ or equol. Further research has observed the effect of estrogen, in the absence of androgens, to increase lean muscle mass by up to 15%, suggesting positive effect of these potent phytoestrogens.
Prevention of chronic disease
With the supplementation of equol, reduction and prevention of estrogen-dependent diseases has been observed. Breast cancer, prostate cancer and osteoporosis are common estrogen-dependent conditions.
Research has demonstrated that bone loss due to estrogen deficiency can benefit from the positive effect of equol supplementation. This mechanism was observed through the ability of equol to inhibit osteoclast formation to prevent the development of osteoporosis.
Equol has also presented chemoprotective effects against specific endocrine-related pathologies. In populations who consume high amounts of soy-based foods, a trend of decreased cancer risk with increased equol is observed. Further research is required to understand this mechanism, whether it is due to the high antioxidant activity of equol or an alternative pathway.
Supplementation of equol
Various studies have observed the effect of equol as both a phytoestrogen and phytoandrogen to promote anabolic activity and prevent the development of chronic disease. Based on the literature, up to 50mg of equol, and/ or 450mg daidzein per day can be supplemented for the previously discussed effects.
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Setchell KDR, Cole SJ. Method of defining equol-producer status and its frequency among vegetarians.The Journal of Nutrition. 2006;136(8):2188-2193. https://doi.org/10.1093/jn/136.8.2188
Gong Y, Lv J, Pang X, Zhang S, Zhang G, Liu L, Wang Y, Li C. Advances in the metabolic mechanism and functional characteristics of equol. Foods. 2023;12(12):2334. https://doi.org/10.3390/foods12122334
Emi Sugimoto, Masayoshi Yamaguchi. Stimulatory Effect of Daidzein in Osteoblastic MC3T3-E1 Cells. Biochemical Pharmacology. 2000;59(5):471–475. Available from: https://doi.org/10.1016/s0006-2952(99)00351-2
Jen-Jih Chen, Hong-Chiang Chang. By modulating androgen receptor coactivators, daidzein may act as a phytoandrogen. The Prostate. 2007;67(5):457-462. https://doi.org/10.1002/pros.20470
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